Maintenance Positions Study Guide

Maintenance Positions Study Guide
Maintenance Positions Study Guide This document is intended to provide information about some of the knowledge necessary to perform duties as an employee in the Maintenance departments at Community College of Allegheny County and may be used to prepare for the pre‐employment assessment conducted during the search process for a vacancy. The information provided in this guide is not intended to be a comprehensive document covering all areas of the assessment. This guide may not be used or referenced during the actual assessment. Version 1.0 TABLE OF CONTENTS
1. Groundskeeping ........................................................................................................ 4
A. Preventative Maintenance – Lawn Equipment ............................................................. 4
B. Pruning ............................................................................................................................. 7
C. Fertilizers ......................................................................................................................... 8
2. Maintenance – General ........................................................................................... 10
A. Door hardware lubricants ............................................................................................. 10
B. Keying ............................................................................................................................ 10
C. Drill bits .......................................................................................................................... 11
D. Woodworking ................................................................................................................ 12
E. Saw blades..................................................................................................................... 15
F. Concrete ordering ......................................................................................................... 18
3. Maintenance – Automotive ..................................................................................... 20
A. Engine oil ....................................................................................................................... 20
B. Automotive Radiators ................................................................................................... 21
C. Automotive Tire changing ............................................................................................ 23
4. Building Construction ............................................................................................ 25
A. Painting Brushes ....................................................................................................... 25
B. Framing/Drywall ............................................................................................................ 29
C. Suspended Ceilings ...................................................................................................... 37
5. HVAC ........................................................................................................................ 43
A. Belt replacement ........................................................................................................... 43
B. Filters .......................................................................................................................... 43
C. Pumps ............................................................................................................................ 46
D. Compressors ................................................................................................................. 48
E. Chillers/Condensers ..................................................................................................... 49
F. Cooling Towers ............................................................................................................. 51
G. Troubleshooting ........................................................................................................... 54
H. Leak detection ............................................................................................................... 55
6. Boilers ...................................................................................................................... 60
A. The Laws of Energy: Thermodynamics ...................................................................... 60
7. Plumbing ................................................................................................................. 62
A. Flush Valve Maintenance ............................................................................................. 62
B. Aerators ......................................................................................................................... 63
C. Soldering ........................................................................................................................ 64
D. Backflow Prevention ..................................................................................................... 65
Maintenance Positions Study Guide 2. 8. Electrical................................................................................................................... 67
A. Conduit installation ....................................................................................................... 67
B. Transformers ................................................................................................................. 73
C. Industrial wiring – 3 Phase ........................................................................................... 74
D. Single-Phasing .............................................................................................................. 76
9. Architectural Drawings ........................................................................................... 79
Maintenance Positions Study Guide 3. 1. Groundskeeping
A. Preventative Maintenance – Lawn Equipment
1) Mowers
1-2-3 Maintenance
At the start of the season, usually spring, there are three main areas to focus on
when it comes to lawn mower maintenance:
a) Change the oil: Even if you don’t think it needs it, do it! The oil should be
changed at the beginning of every season. Over the course of the cutting
season, dirt and other impurities will collect in the oil and those things will ruin an
engine. Check the mower’s owner’s manual for the proper procedure.
b) Change the spark plug: That little space at the end of the plug where the metal
end bends at a 90 degree angle is called the gap. Many manufacturers are now
packaging new plugs with the gap pre-set, so it’s as simple as removing the old
and installing the new. However, it’s still a good idea to double-check the gap
with an inexpensive spark plug gap tool just in case. Many people like to change
the plug every year so you’re starting every cutting season with a new spark
c) Clean the air filter: If the filter in your mower is an accordion-style paper type,
simply remove the filter cover and blow out all the debris with a high-pressure air
hose. If the filter is made from foam, wash it in a water and detergent solution, let
it dry, and apply a few drops of oil to it. In some rare cases, you may need to
replace the filter, but most of the time, a simple cleaning will do.
2) Blades
a) It takes a little extra effort to remove the blade and sharpen or replace the
blade. Every year, though, this should be done prior to the first cutting. You
need to have a sharp blade when cutting grass, otherwise it doesn’t cut the
grass but, tears it instead, which can lead to a diseased lawn. Before
removing the blade, be sure to detach the spark plug wire to prevent the
mower from accidently starting. Then tilt the mower up and use a wrench to
loosen the bolt that holds the blade on by turning it counter clockwise.
b) Sharpening a blade can be done with a metal file, sharpening stone, or a
motorized grinder. Regardless of the method used, follow the existing
beveled edge on the blade by passing the file over the blade in the same
direction each time. An even easier way to sharpen the blade is to use a
small grinding attachment for your cordless drill. Just place the blade in a
bench vice and you can hone the edge with no trouble.
3) Push Mowers
a) For a small lawn, a simple push mower is perfect. While some workers use push
mowers to take care of large lawns, it takes several hours of work and defeats
the whole purpose of making the chore easier. A larger cutting deck is a good
feature. Many small mowers start at around 19”, but 21” is better. Also, think
about how easy it is to crank and the type of bagging attachment (a rear bagger
is easier to maneuver).
b) Battery powered cordless models are becoming more and more popular. Not
only are they quieter and more environmentally friendly than gas powered
models, but cordless electric mowers greatly reduce the maintenance needed,
since they don’t need oil changes, spark plugs, or air filters.
Maintenance Positions Study Guide 4. 4) Riding Mowers
For a large lawn, riding mowers are the machine of preference. Professional services
use ZTR (Zero Turn Radius) mowers, which can turn on a dime. The biggest
drawback for many homeowners is trying to operate the ZTR’s with the two separate
directional levers. The cutting decks for riding mowers start at 42”. While most
workers don’t need one that’s too big, a 48”-50” model is ideal.
Cutting Tips
Here are a few quick tips that will keep your lawn looking great:
a) Don’t cut wet grass: Aside from having a tendency to clog the machine and leave
clumps of wet grass all over the yard, wet grass won’t cut easily. It tears, just as it
does with a dull blade.
b) Set the cutting height to at least 1½”: Taller grass will hold moisture better and
will also allow the root system to “grab hold” of the soil better, which means a
healthier lawn. Never cut more than 1/3 of the existing height. Bluegrass mixed
turf should be mowed to a height of 2 ½ ” to 3”
c) Don’t mow in the same direction every time you cut: For example, one week mow
north to south. The next week, mow east to west. This prevents ruts from forming
in the yard and also lets the grass grow thicker.
d) Use a grass catcher for the first cut and last cut of the season: Use the mulching
feature the rest of the time to reduce yard waste and add nutrients back into the
5) Annual Maintenance
Lawnmowers need annual maintenance to keep running and cutting right. Blades
need to be sharpened and balanced. Caked-up grass needs to be removed from
underneath so it won't rust out the cutting deck. Oil needs to be changed. Things
need to be lubricated. Nuts and bolts work loose and need to be tightened. Doing
annual maintenance can keep your mower running years longer, rather than having
to buy a new one. Here are the normal annual maintenance times:
a) Walk-behind mower annual maintenance (no repairs needed): 1 hour.
b) Riding mower annual maintenance (no repairs needed): 1-1/2 hours.
c) Zero-turn mower annual maintenance (no repairs needed): 2 hours.
6) Putting Your Mower Up For The Winter
a) The last time you cut grass put just enough gas in the mower to finish cutting.
When you're done, run the engine till it runs out of gas. Run ALL the gas out of it.
If there is too much gas in the tank to do that, either drain it out, or put fuel
stabilizer in and run the engine for a few minutes to get the stabilizer down into
the carburetor.
b) Change the oil. Most mower engines use straight 30 weight detergent oil. Walkbehind mowers have the oil drain plug underneath. Use a 3/8 drive ratchet with
an extension. The end of the extension fits the drain plug exactly. Raise the
mower on it's side, put a large pan underneath, take the oil drain plug out, set the
mower back down, let the oil run out for a few minutes, then put the drain plug
back in. Riding mowers usually have the oil drain on the side of the engine. Put a
large pan underneath, take the drain plug out, let the oil run out for a few
minutes, then put the plug back in. Fill the engine with oil. Most walk-behind
mowers take up to 1 quart. Most riding mowers take up to 2 quarts. Add oil
slowly, stopping frequently to check the oil level on the dipstick.
Maintenance Positions Study Guide 5. c) Other lubrication. Steering sector gear and steering linkage needs to be lubed so
the mower is easy to steer. Steering arms and front wheel bearings with grease
fittings need to be lubed with a grease gun. Go around the mower with an oil can
and oil every moving point on the mower, every linkage point, etc, particularly the
blade raise / lower arm and cutting deck linkage, blade engage arm and cutting
deck linkage, etc. Most of that linkage is underneath the mower. You'll have to
lay down on the driveway so you can see under there and oil those linkage
points. (When lubricating bearings on a rider mower, only one pump of grease
into the bearing fitting is necessary.)
d) Air filter / fuel filter / spark plug. Blow the air filter out with compressed air. If the
fuel filter is a few years old put a new one on. Clean and gap the spark plug. By
the way, spark plugs hardly ever give problems. If your mower won't start it's
usually a carburetor/fuel problem.
e) Sharpen/balance the blade(s) so it will be ready to go next spring. On a riding
mower and zero-turn mower you'll have to jack up the front of the mower and
raise the cutting deck all the way up to get the blades off. Sometimes blade
bolts/nuts are very tight. Use an air-powered impact wrench to remove them.
f) Clean underneath the cutting deck. While you have the blades off to sharpen
them, get under the cutting deck with a scraper and scrape all the caked up
grass out. Getting all that grass out from underneath the cutting deck will keep it
from rusting, improve air flow, help grass blow out easier, and help the blades cut
g) Check belts and pulleys for excessive wear. Check the drive belt(s) and blade
belt(s) for excessive wear, cuts, etc. Replace as needed. Turn the blade spindles
by hand and feel for roughness and play in the bearings. Be sure to back off the
blade brake so the spindle turns. Turn the pulleys by hand and feel for roughness
and play in the bearings. Blade spindles and pulleys should turn smoothly with no
roughness and no play (no looseness, no wobble). If you feel roughness,
grinding, looseness or play in the bearings, it's time to replace them. Replace
them now, before they go out completely. On some mowers you can replace just
the bearings. On some mowers you have to replace the entire blade spindle
assembly or the entire pulley.
h) Note: Sometimes it's easier to unhook the cutting deck from the mower, pull it
out, and lean it up against the mower to sharpen blades, clean grass out, check
belts, check pulleys, check blade spindles, etc.
i) Inflate tires to proper pressure. Recommended pressure is on the side of the tire.
Sometimes it's difficult to see, but it's there.
j) Disconnect the battery. All you have to do is disconnect the negative battery
cable. This is also a good time to clean the cables and battery terminals. After
cleaning them, smear grease on them with a small brush to prevent corrosion,
especially the positive terminal.
k) Hose off the entire mower. Wash all the grass and dirt off the entire mower. Hit
everything, including the engine, battery area, and top of the cutting deck.
l) Do steps 1 - 4 and 10 on your weedeater and anything else with an engine that
you won't be using during the winter.
m) Getting the gas out of it, or adding fuel stabilizer, is the most important thing. The
gas goes stale, in some cases varnishes up the carb, and the mower won't start
next spring. Then you would need to drain the old gas out, pull the carb off, take
it apart, clean it, put it back on the mower, blow the fuel line out, sometimes put a
new fuel filter on, and put fresh gas in for the mower to start and run right.
Maintenance Positions Study Guide 6. n) Keep the battery charged during the winter. Put a trickle-charger on it, or check
the voltage once per month during the winter. If it drops below 12 volts, recharge
it. Many batteries go bad during the winter because they're allowed to discharge
o) Keep tires inflated during the winter. If a tire goes flat, sometimes it breaks the
bead loose from the rim. You'll have to reseat the bead to inflate the tire again.
Avoid that by keeping the tires inflated during the winter. Check them about once
per month.
B. Groundskeeping - Pruning
1) A tree may need pruning for a variety of reasons:
a) to remove diseased or storm-damaged branches
b) to thin the crown to permit new growth and better air circulation
c) to reduce the height of a tree
d) to remove obstructing lower branches
e) to shape a tree for design purposes
Once the decision has been made to prune, your next decision is whether or not to
tackle the job yourself. In the case of a large tree where you want to remove
branches in the upper area of the crown, it may be best to hire experts. Large tree
pruning, in particular, can require climbing and heavy saws or even cherry-pickers
and chain saws. However, there are new tools available that can make this a
manageable job.
2) How to Prune
Whether the tree is large or small, the key is to prune the unwanted branch while
protecting the stem or trunk wood of the tree. Tree branches grow from stems at
nodes and pruning always takes place on the branch side of a stem-branch node.
Branches and stems are separated by a lip of tissue called a stem collar which grows
out from the stem at the base of the branch. All pruning cuts should be made on the
branch side of this stem collar. This protects the stem and the other branches that
might be growing from it. It also allows the tree to heal more effectively after the
prune. To prevent tearing of the bark and stem wood, particularly in the case of
larger branches, use the following procedure:
a) Make a small wedge shaped cut on the underside of the branch
just on the branch side of the stem collar. This will break the bark
at that point and prevent a tear from running along the bark and
stem tissue.
b) Somewhat farther along the branch, starting at the top of the
branch, cut all the way through the branch leaving a stub end.
c) Finally, make a third cut parallel to and just on the branch side with in 1/2” of the
of the stem collar to reduce the length of the stub as much as possible. A similar
procedure is used in pruning one of two branches (or one large branch and a
stem) joined together in a 'u' or 'v' crotch. This is known as a drop crotch cut.
Make the first notch cut on the underside of the branch you're pruning well up
from the crotch. For the second cut, cut completely through the branch from
inside the crotch well up from the ridge of bark joining the two branches. Finally,
Maintenance Positions Study Guide 7. to shorten the remaining stub, make the third cut just to one side of the branch
bark ridge and roughly parallel to it. (Source:
C. Fertilizers
1) All fertilizers are labeled with three numbers that represent the primary nutrients that
plants need: nitrogen, phosphorous and potassium. They are always listed as a
percentage of those nutrients and always in that order. For example, a 4-1-2 fertilizer
contains 4 percent, by weight, nitrogen, 1 percent phosphorous and 2 percent
potassium. These can occur in different ratios and combinations, but they all
represent the strength or concentration of the fertilizer. So an 8-2-4 would be twice
as concentrated as a 4-1-2. This is important when comparing prices because it
would take twice as much of the second fertilizer to equal the same amount of
nutrient as the first.
2) What do the Three Primary Nutrients do? –
Nitrogen is very important in plants for good foliage growth and dark green color.
Phosphorous is important for rooting and also for blooming, and potassium is
important for cold hardiness and plays a role in fruiting and blooming. It is possible to
use a balanced fertilizer, one where the three numbers are equal or close to one
another (15-15-15), throughout the growing cycle. A better plan is to look for a
fertilizer brand that has at least two formulas to accommodate different stages in the
plants growing cycle and/or different varieties of plants.
For vegetables grown mostly for their leaves (salad or other greens) a fertilizer with
more nitrogen than anything else (a higher first number) is best. For vegetables that
flower first like peppers and tomatoes, a fertilizer with a higher proportion of
phosphorus (a higher middle number) works well. Alternatively, some gardeners
produce great results by using a high growth (high nitrogen) formula for the
beginning of the growth cycle and then switch to a high bloom (high phosphorus)
fertilizer when the plants begin to flower.
3) Micronutrients:
The three primary macronutrients have been discussed, but what about the other
micronutrients that plants need to stay healthy. Fortunately the better fertilizer
companies have added these micronutrients to their products as well. It is a good
idea to look for a brand of fertilizer that includes additives to address necessary
micronutrients. The following is a list of micronutrients and their functions:
a) Calcium (Ca)
1) Strongly influences proper soil pH
2) Essential to strong cell wall structure and cell division
3) Can improve soil structure and water retention
b) Magnesium (Mg)
1) Plays an important role in photosynthesis and chlorophyll production
2) A necessary component in many essential enzyme systems within plants
3) Important in aiding the plants use of phosphorous
c) Sulfur (S)
1) Works with nitrogen to produce new protein for plant growth
2) Plays an important role in the utilization of oxygen
3) Influences the level of activity of soil microorganisms
d) Iron (Fe)
1) Necessary for the formation of the chlorophyll
Maintenance Positions Study Guide 8. 2) Aids in the activation of a number of biochemical processes within the plant
e) Manganese (Mn)
1) Important to the formation of chlorophyll and the activation of the initial growth
f) Zinc (Zn)
1) Necessary for the production of chlorophyll
g) Copper (Cu)
1) Important in the synthesis of certain plant growth substances
2) Serves as an activator for several essential enzymes
h) Chlorine (Cl)
1) May help in the regulation of osmotic pressure within the plant cell
4) Both organic and chemical fertilizers are available in dry and liquid forms. Once a
decision is made concerning which type to use, the information can be applied to
compare and select the most economical brands. Regardless of which brand is
selected it is a good idea to have a few favorites and switch fertilizers every few
Maintenance Positions Study Guide 9. 2. Maintenance – General
A. Door hardware lubricants
1) When you insert your key into the lock and it is difficult to turn, or even to slide the
key in or out of the keyhole, the lock probably needs to be lubricated. To confirm this,
try using the key when the door is standing open. If it is still difficult to operate, then
the problem lies in the lock.
2) There are a couple different types of lubricants that can be used in a lock, but we
prefer graphite powder. Graphite powder is odorless and tends to stay in the lock
rather than sticking to the key. If you use a petroleum based oil, it can make your
keys oily and worse, dust tends to stick to it inside the lock and become gunky.
Silicone products are also acceptable. However, whichever you choose, stick with
that lubricant. Mixing lubricants is a sure way to gunk up a lock.
3) Graphite powder comes in a small squeeze tube. Simply uncap the tube, place the
tip of the tube in the keyhole, tip the tube up slightly and give a couple of squeezes
to blow the powder into the lock. Now insert your key repeatedly and turn the lock
repeatedly to work the powder into the lock. You should also lubricate the bolt by
squeezing graphite into the cracks around the bolt or latch on the edge of the door.
Some lubricant manufacturers also have silicone based products that do well.
4) The lock should operate more smoothly now. If it is still difficult to operate, the
problem may lie in the doorknob itself, the latch mechanism or the alignment of the
door with the latch plate in the door jamb. Disassembly of the door knob and latch
may help to identify the problem. If pulling or pushing on the door makes it easier to
unlock, then the door's alignment is the problem. Adjustment of strike plate, on the
door jamb, may help correct this problem.
B. Keying
1) What is a Master Key System?
a) A master key system is a set of locks that are keyed so that they each may
have an individual key, called a pass key, yet all are opened by an additional,
special key called a master key. These locks would be described as keyed
different and master keyed.
b) Within a master key system, groups of locks can be keyed alike, so that the
same key operates all locks in the group, plus all locks in the group are
operated by the master key. These locks would be described as keyed alike
and master keyed.
c) Under the master, groups of locks can be keyed different, keyed to a
submaster, and keyed to the master. For example, you might have three
buildings. Each building has six locks keyed differently and a submaster key
that operates all the locks within a single building. The master key opens all
Maintenance Positions Study Guide 10. the locks in all three buildings, but the submaster from one building will not
open any lock in either of the other two buildings.
d) A grand master key might be necessary if a property manager is responsible
for groups of buildings, for example. Each group of buildings would be under
a separate master key; each building would have a submaster key; and
overall would be the grand master key that would open everything.
e) The weakness of a master key system is in the key control. If the wrong
person gets a copy of the grand master key, every lock in the system may
have to be changed.
f) The way a master key system is laid out determines the ability that each
individual key holder may have to operate any given lock. Therefore it is best
to have a clear idea of who needs to get in before you start.
2) Identify the Doors
If your master key system is going to be part of new construction, use the door
numbers from the architect's hardware schedule to identify the doors. If this is an
existing facility, you can assign names or numbers to the doors as you see fit. The
point of this is to be able to match up a key with a door in the future so that you will
be able to look at your keying schedule and identify what key(s) open which door.
C. Drill bits
1) Drill Accessories Safety Tips
a) When drilling with hole saws or large capacity bits, use a drill press or clamp the
material to the table. If this is not possible, beware that the drill bits can bind in
the material if the drill is not held exactly level with the hole. If the drill bit binds, it
may stop moving, but the drill may continue to move, taking your hand with it.
b) Avoid burning the workpiece by drilling at slower speeds when using a hole saw
or large capacity cutter.
c) Never try to free up a jammed drill bit by stopping and starting the drill.
d) Always unplug the drill before changing bits and accessories.
e) Always have secure footing when drilling. Carefully brace yourself when drilling
on a scaffolding or ladder.
f) Always make sure the drill chuck is securely tightened around the spindle of the
drill bit.
2) Twist Drill Bit
a) Used in both wood and unhardened metals to make clearance holes for bolts,
screws, etc., and to make holes for tapping.
b) Bits marked HS (high speed) or HSS (high speed steel) are suitable for drilling in
metals or wood,
c) Bits made of carbon steel should be used only in wood and not in metal as they
are more brittle and less flexible than HSS bits.
3) Hole Saw
a) Cup-shaped blade with a bit in the middle, called a
b) Used for cutting holes in wood, plastic, plaster and light metals.
c) Available in a range of diameters
Maintenance Positions Study Guide 11. 4) Brad Point Bit
a) Used for wood drilling only.
b) Tip has a screw-type point leading the drill flute that prevents drill walking.
c) Helps prevent splintering, as the brad point is the first part of the drill to emerge,
allowing the user to back the drill out of the hole and finish from the other side of
the material.
5) Spade Drill Bit
a) Used in electric drills and drill presses for fast drilling of
holes in wood.
b) Bits have a forged, flat paddle with a point and cutting edges on one end.
c) Bits are heat treated and cutting angles finish ground.
d) Electricians use them for drilling clearance holes for wire in floor beams.
6) Countersink Bits
a) Widen holes so flathead screws may be flush mounted below the surface for a
finished appearance.
b) The counterbore is another version that makes a straight-walled hole so there’s
room for a wooden plug.
7) Auger Drill Bit
a) Most commonly used with a brace for drilling holes in
b) Length varies from 7" to 10".
c) Dowel bits are short auger bits from 5" long.
d) Long (ship) auger bits range from 12" to 30
8) Expansion Bit
a) Takes the place of many larger bits.
b) It is adjusted by moving the cutting blade in or out by a geared
dial or by a lockscrew to vary the size of the hole
9) Masonry Bit
a) Also known as a carbide-tipped bit.
b) Used in electric drills, drill presses or hand drills for drilling holes in brick, tile,
cement, marble and other soft masonry materials.
c) Some versions have a titanium nitride-coated tip.
d) Feature two machined in spiral threads, one for each cutting edge, to provide
passageways for all dust and cuttings from the bottom of the hole.
e) Diameters of carbide tips are the same as the full diameter of the body.
10) Tile Bit
a) Used for drilling ceramic tile and glass.
b) Has a ground tungsten carbide tip.
c) Best if used with a variable speed power drill at a low speed.
11) Step Bit
a) Has a graduated design so that various sized holes can
be cut without changing bits.
Maintenance Positions Study Guide 12. b) Designed for use with power drills and has self-starting tips eliminating the need
for center punching. Can be used on all materials, but especially designed for
use on metals.
12) Circle Cutter
a) Also known as a fly cutter.
b) Has a cutting blade attached to a horizontal arm. It can cut
holes up to 7” in diameter.
c) Primarily used on a drill press
D. Woodworking
1) Types of Wood for Woodworking
a) Solid wood — that is, wood cut into boards from the trunk of the tree — makes
up most of the wood in a piece of furniture. The type of wood you choose
determines the beauty and strength of the piece. Many varieties of wood are
available and each has its own properties. The following sections introduce you
to the most common types of soft- and hardwoods.
b) Softwoods aren't weaker than hardwoods. Softwoods come from coniferous trees
such as cedar, fir, and pine and tend to be somewhat yellow or reddish in
appearance. Because most coniferous trees grow fast and straight, softwoods
are generally less expensive than hardwoods.
2) The following is a list of common softwood varieties and their characteristics.
a) Cedar
1) The most common type of cedar is the western red variety. Western red
cedar, as its name implies, has a reddish color to it. This type of wood is
relatively soft (1 on a scale of 1 to 4), has a straight grain, and has a slightly
aromatic smell. Western Red cedar is mostly used for outdoor projects such
as furniture, decks, and building exteriors because it can handle moist
environments without rotting. Western red cedar is moderately priced and can
be found at most home centers.
b) Fir
1) Often referred to as Douglas Fir, this wood is very soft, has a straight,
pronounced grain, and has a reddish brown tint to it. Fir is most often used for
building; however, it's inexpensive and can be used for some furnituremaking as well. It doesn't have the most interesting grain pattern and doesn't
take stain very well, so it's best to use it only when you intend to paint the
finished product. Douglas fir is pretty hard, rating 4 on a scale of 1 to 4.
2) This wood is worth mentioning because it is very common at your local home
center and it's so inexpensive you'll probably be tempted to make something
with it.
c) Pine
1) Pine comes in several varieties, including Ponderosa, Sugar, White, and
Yellow, and all of them make great furniture. In some areas of the country
(especially southwest United States), pine is the wood to use. Pine is very
easy to work with and, because most varieties are relatively soft, it lends itself
to carving.
Maintenance Positions Study Guide 13. 2) Pine generally takes stain very well (as long as you seal the wood first),
although Ponderosa pine tends to ooze sap, so be careful when using this
stuff. Pine is available from most home centers, but it's often of a lesser
grade than what you can find at a decent lumberyard.
d) Redwood
1) Like cedar, redwood is used mostly for outdoor projects because of its
resistance to moisture. Redwood (California redwood) is fairly soft and has a
straight grain. As its name suggests, it has a reddish tint to it. Redwood is
easy to work with, is relatively soft (2 on a scale of 1 to 4), and is moderately
priced. You can find redwood at your local home center.
e) Hardwoods
1) Most woodworkers love to work with hardwoods. The variety of colors,
textures, and grain patterns makes for some beautiful and interesting-looking
furniture. The downside to hardwoods is their price. Some of the more exotic
species can be too expensive to use for anything more than an accent.
3) Following is a list of common hardwoods and their characteristics:
a) Ash
1) Ash is a white-to-pale-brown colored wood with a straight grain. It's pretty
easy to work with (hardness of 4 on a scale of 1 to 5) and takes stain quite
nicely, but ash is getting harder and harder to find. You won't find ash at your
local home center — it's only available from larger lumberyards. Ash is a
good substitute for white oak.
b) Birch
1) Birch comes in two varieties: yellow and white. Yellow birch is a pale yellowto-white wood with reddish-brown heartwood, whereas white birch has a
whiter color that resembles maple. Both types of birch have a hardness of 4
on a scale of 1 to 5. Birch is readily available and less expensive than many
other hardwoods. You can find birch at many home centers, although the
selection is better at a lumberyard.
2) Birch is stable and easy to work with. However, it's hard to stain because it
can get blotchy, so you might prefer to paint anything that you make with
c) Cherry
1) Cherry is a very popular and all-around great wood; easy to work with, stains
and finishes well with just oil, and ages beautifully. Cherry's heartwood has a
reddish-brown color to it and the sapwood is almost white. Cherry has a
hardness of 2 on a scale of 1 to 5. This is a very common wood for furnituremaking and is available from sustainably-grown forests. You won't find cherry
at your local home center, so a trip to the lumberyard is necessary if you want
to use it. Because it's in demand, cherry is getting somewhat expensive
compared to other domestic hardwoods, such as oak and maple.
d) Mahogany
1) One of the great furniture woods, mahogany (also called Honduran
mahogany) has a reddish-brown-to-deep-red tint, a straight grain, medium
texture, and a hardness of around 2 on a scale of 1 to 5. It takes stain very
well and looks great with just a coat (or 10) of oil.
2) The only drawback is that mahogany isn't being grown in sustainable forests.
Forget going to your home center to get some — the only place to find
mahogany is a decent lumberyard (and it'll cost you).
Maintenance Positions Study Guide 14. e) Maple
1) Maple comes in two varieties: hard and soft. Both varieties are harder than
many other woods; hard maple is so hard (a 5 on a scale of 1 to 5) that it's
difficult to work with. Soft maple, on the other hand, is relatively easy to work
with. Because of their fine, straight grain, both varieties are more stable than
many other woods. They also tend to be less expensive than other
hardwoods. You won't find maple at your local home center, but most
lumberyards have a good selection of it.
f) Oak
1) Oak is one of the most used woods for furniture. Available in two varieties —
red and white — oak is strong (hardness of about 4 on a scale of 1 to 5) and
easy to work with. White oak is preferred for furniture-making because it has
a more attractive figure than red oak (white oak is also resistant to moisture
and can be used on outdoor furniture).
g) Poplar
1) Poplar is one of the less expensive hardwoods. It's also fairly soft (1 in
hardness on a scale of 1 to 5), which makes it easy to work with. Poplar has
a white color with some green or brown streaks in the heartwood. Because
poplar is not the most beautiful wood, it's rarely used in fine furniture and if it
is, it's almost always painted. Poplar can be a good choice for drawers
(where it won't be seen) because it is stable and inexpensive. You can find
poplar at larger home centers, but a lumberyard will have a better selection.
h) Teak
1) Teak is becoming rarer as the days go on, but it is the staple for fine outdoor
furniture. Teak is highly weather-resistant and beautiful (not to mention
expensive — can you believe almost $24 a board foot?). Teak has an oily
feel and a golden-brown color. It rates a 3 on a scale of 1 to 5 for hardness
and is only available from larger lumberyards and specialty suppliers.
i) Walnut
1) With a hardness of about 4 on a 1 to 5 scale, walnut is a rich brown wood
that's easy to work with. Unfortunately, walnut is somewhat expensive
(usually around $8 a board foot) and finding large boards for big projects is
getting difficult. In spite of this, walnut is still a great wood to work with and
lends itself nicely for use as accents and inlays to dress up a project. You
won't find walnut at your local home center and you may need to special
order it from a lumberyard if you want a large quantity.
E. Saw Blades
1) Saws Safety Tips
a) Always wear proper eye protection, such as safety glasses or a face shield.
b) When selecting any type of saw, be sure to pick one that is the right size and
design for the type of material being cut.
c) The right saw handle should keep the user’s wrist in somewhat of a natural
position that is horizontal to the piece being cut.
d) Always make sure the piece being cut is free of objects such as screws and
nails, that could make the saw buckle,.
e) To start the cut properly, place your hand with the thumb in an upright
position pressing against blade. Go slow at first to prevent blade from
Maintenance Positions Study Guide 15. jumping off the cut line. Then, after the blade is engaged, begin with partial
cutting strokes and be sure to set the saw at the proper angle.
f) During the cut, pressure is applied only during the downstroke.
g) Be sure the stock being cut is secured firmly in place.
h) When cutting longer stock, always be sure the stock is properly supported.
i) Pull teeth can be a safety hazard. Always make sure the teeth and blades are
properly sharpened, set and cleaned.
j) Always protect the teeth of any saw when the tool is not in use.
k) When using hacksaws, make sure the bade is secured with the teeth pointing
forward and that the frame is aligned properly.
l) When cutting with a hacksaw, use the full length of blade in each cutting
2) Rip Saw
a) Has large, chisel-shaped teeth, usually 5-1/2 teeth per inch, and is made to
cut with the wood grain.
b) Blade lengths measure from 24" to 28".
c) Teeth are cross-filed to ensure that the chisel point is set square to the
direction of cutting for best performance.
d) This saw is best held at a 60º angle to the surface of the board being cut. The
ripping action of the saw produces a coarse, ragged cut that makes the saw
unsatisfactory for finish work.
3) Crosscut Saw
a) Designed for cutting across wood grain and produces a smoother cut than rip
b) Has teeth shaped like knife points to crumble out wood between cuts.
c) The most commonly used crosscut saws are 10- to 12-point for fine work and
7- or 8-point for faster cutting. 10 teeth per inch is considered general
d) Blade lengths range from 20" to 28", with 26" the most popular.
e) Can also be used to cut plywood.
f) Best cutting angle for this saw is about 45º.
4) Hacksaw
a) Is a fine-toothed saw designed to cut metal or plastic. Hacksaws consist of a
blade held in a steel frame with relatively high tension to hold the blade rigidly
straight. High-tension models (with tension to 32,000 p.s.i.) are also available.
b) Blades come in coarse-, medium (18 tpi), fine (24 teeth per inch and very
fine-toothed (32 tpi). Regular or standard blades are used for generalpurpose cutting; high-speed or bi-metal blades for cutting hard, extra-tough
c) Most models can be adjusted to hold various blade lengths. Some have both
horizontal and vertical positions for blades. Others provide blade storage.
d) A close-quarter (or utility) hacksaw holds and positions a hacksaw blade so it
can be used effectively in narrow spaces and slots.
e) Replacement blades include rod saw blades capable of cutting through most
hard materials—spring and stainless steel, chain, brick, glass and tile.
5) Compass or Keyhole Saw
a) Cuts curved or straight-sided holes.
Maintenance Positions Study Guide 16. b) Saw blades are narrow, tapered nearly to a point to fit into most spaces.
c) Blades come in three or four styles that can be changed to fit the job.
d) Some models have induction-hardened teeth for longer life without
e) Keyhole saws are small compass saws with finer teeth that can cut metal.
f) Turret head keyhole blades can be rotated and locked in several positions for
easier cutting in tight, awkward spots.
6) Coping Saw
a) Used for cutting irregular shapes, curves and intricate decorative patterns.
b) Name comes from saw’s usefulness in coping back the joints of molding
when fitting two pieces together.
c) Saw consists of a thin blade and a C-shaped steel tension frame.
d) The removable blade is typically 6-1/2" long.
7) Backsaw
a) Is a thick-bladed saw with a stiff, reinforced back to provide the rigidity
necessary in precision cutting.
b) It varies in length from 10" to 30" and is found in tooth counts from seven to
14 teeth per inch.
c) Used with miter boxes to cut miters.
8) Bow Saw
a) Consists of a tubular steel frame and a saw blade for fast cutting of all woods.
b) The bow saw's frame is important, since the thin blade, usually 3/4" wide,
must be held under high tension for fast cutting.
c) Advantages of this general-purpose saw are its all-around utility and light
d) Some bow saws are designed to hold hacksaw blades as well as standard
bow saw blades. These multi-purpose saws can be used to cut wood, metal
or plastic.
9) Dovetail Saw
a) Similar to a backsaw, with stiff reinforced back, only smaller with finer teeth.
b) Used for fine finish cuts, such as cutting dovetail joints in woodworking.
c) Common saw for trimming molding and furniture repair.
d) Can also be used to cut plastics and laminates.
10) Toolbox Saw
a) Also called Panel Saw or Short Cut Saw.
b) Good for ripping, crosscutting and general cutting of lumber, plywood and
particleboard and plastic materials.
11) Drywall Saw
a) Resembles a kitchen knife in design and is used to cut drywall and
plasterboard in the same fashion as a keyhole saw, such as for sawing holes
for electric outlets and switchplates.
b) The saw is self-starting with a sharp point for plunge cuts.
c) It may also have induction teeth for longer life without sharpening.
Maintenance Positions Study Guide 17. 12) Plywood Saw
a) Is specially designed for sawing plywood, veneers, laminates and moldings.
b) The blade, which cuts on the push stroke, is curved downward at the end to
allow user to start cuts in the center of a board.
c) Not designed for cutting solid wood.
d) Standard saw lengths are 12"-13", generally with 14 teeth per inch.
13) Pull Saw
a) Is similar to most traditional saws except the teeth are designed to cut with a
pulling motion.
b) Pull saws cut wood faster and with less effort because of the thinner and
more flexible blade.
c) The saws feature teeth diamond-ground on three cutting edges.
d) Because of the flexibility of the blade and the minimal set to the teeth, the
saws are excellent for flush cutting.
e) Mini pull saws that cut sharply on the pull stroke are used for precision
14) Plastic Pipe Saw
a) Designed to cut PVC and ABS plastic.
b) Can also cut wood and drywall.
15) Retractable Saw
a) Comes in a variety of designs and is engineered for the blades to either
retract or fold back into a plastic or wooden handle.
b) Also called a folding saw.
c) Some models have combination features, such as utility knives, on end
opposite saw blade.
16) Miter Box
a) Used to help cut exact angles for wood trim and rafters.
b) Better models provide a mechanism for a backsaw.
c) They are made of plastic, hardwood or aluminum.
d) Some boxes feature magnetic mount guides. The magnets grasp and hold
the saw to the miter box saw guide or hold the saw blade to the plane of the
saw guide.
F. Concrete ordering:
1) Calculations
a) Calculate the right volume. Concrete is always ordered in cubic yards. First figure
out the cubic footage, then convert to yards by dividing by 27. Here’s how:
1) multiply the length of your project times the width times the depth (4 in. = 33
ft.) and divide the total by 27.
2) Using a sidewalk as an example: 60 ft. (long) x 4 ft. (wide) x .33 ft. (deep) =
79.2 cu. ft. ÷ 27 = 2.93 cu. yards. You can also figure your cubic yards by this
example: length times width, divided by 12, times thickness, divided by 27.
Maintenance Positions Study Guide 18. 3) Using the figures from above example. 60 ft ( length ), times 4 ft (width),
divided by 12, times 4 inches (thickness), divided by 27 = 2.96 cubic yards.
4) Concrete is cheap and nothing is worse than coming up short (except rain). A
good rule of thumb is to order an extra 5 percent rounded up to the next 1/4
yd. to handle spillage and uneven bases.
b) Order from the nearest supplier. Get fresh concrete mixed near the site, not
mixed across town by some company with a lower price.
c) Ask for 5 percent “air entrainment” in the mix. Suppliers add a chemical that traps
microscopic air bubbles to help the concrete handle the expansion and shrinkage
caused by climatic changes such as freezing.
d) Get the right strength. Tell them you’re pouring an exterior sidewalk and they’ll
recommend the correct “bag mix” (ratio of cement to gravel and sand). In cold
climates, they’ll probably suggest at least a 3,000-lb. mix. That means concrete
that’ll handle a 3,000-lb. load per square inch without failing.
2) Tips
a) The truck comes with the concrete premixed with the correct water content. But
the driver may send a little concrete down the chute and ask if you’d like more water
added. Unless the mix is too dry to get down the chute, forget it. The mix should be
thick—not runny. Wetter concrete may be easier to place (fill the forms), but the
wetter the mix, the weaker the concrete.
Maintenance Positions Study Guide 19. 3. Maintenance – Automotive
A. Engine oil
1) Choose Your Oil
a) Your owner's manual for your vehicle should recommend a certain grade of
oil to be used under normal driving conditions as well as the number of miles
that you can drive your vehicle before changing your oil (maximum drain
interval). However, if you drive under severe conditions such as extreme
temperatures, frequent short trips, stop and go traffic or towing and hauling,
the extra strain on your engine will necessitate more frequent changes. The
average driver generally doesn't realize it but the vast majority of their driving
falls into this category, which is why most mechanics will refer to and change
oil by the shorter drain interval recommended by the manufacturer for use in
"severe" driving conditions.
b) As a general rule of thumb, change your motor oil and oil filter every 3,000
miles or every 3 months, whichever comes first. This strategy will provide
superior engine protection and long engine life. (Be certain to check your
owner's manual for special conditions and do not exceed warranty
2) Prepare Your Vehicle
a) Always be certain to consult your owner's manual for specific safety
precautions before climbing under your vehicle.
b) Never use a bumper jack to hold your vehicle up - it is simply too unstable.
Portable wheel ramps are ideal and much safer. Wheel ramps will tilt the car
just enough to allow you to slide underneath. After making sure that you are
on level ground, drive your vehicle up onto the wheel ramps so that the front
tires are elevated. Set your emergency brake and brace both rear wheels
with wooden blocks to prevent the vehicle from rolling. Put your vehicle in first
gear if you have a manual transmission and in Park if you have an automatic
transmission. Cold oil will not drain properly so idle your engine for about 310 minutes to bring it to normal operating temperature (never start your
engine without oil). Then switch off the engine and raise the hood to locate
and loosen the oil sump cap to avoid creating a vacuum. This will allow the oil
to drain from the bottom more freely.
3) Drain the Old Oil
a) Locate the oil drain plug on the underside of your vehicle. It should be located
at the bottom rear end of the engine sump or oil pan. Be sure not to loosen
the automatic transmission drain plug by mistake. (It is usually located a bit
further back.)
b) Place the drain pan underneath the drain plug and slightly toward the back.
Using your wrench, turn the plug counterclockwise until it rotates freely.
Finish removing the plug by hand. At this point, be careful of the oil since it
may release rapidly and is likely to be rather hot. Try not to drop the plug into
the pan, but don't worry if you do!
Maintenance Positions Study Guide 20. 4) Remove the Oil Filter
a) Next, loosen the oil filter - which may be warm - by turning it counterclockwise
with a filter wrench. Complete the removal by hand, taking care not to touch
the hot exhaust manifold. The oil filter may be filled with oil and feel slightly
heavy, so carefully ease it down and away from the engine and tip its
contents into the drain pan.
5) Replace the Oil Filter
a) Take your rag and wipe in and around the filter seat on the engine. Then take
a new filter and use your finger to apply a light film of oil (new or used) to the
gasket (the circular edge of the filter itself). This film will act as a sealant. Now
gently screw the new filter onto the threaded oil line, turning it clockwise. If it's
aligned properly, the filter should thread on easily. Hand-tighten the filter
approximately ½ to ¾ of a turn after the gasket makes contact with the
mounting surface. Make sure the filter is mounted snugly, but be gentle,
Hercules; you don't want to over-tighten.
b) Be sure to clean the copper gasket and the oil plug. Use a paper towel or rag
to clean old oil or road dirt from the area on the oil pan near the oil plug hole
before re-installing the drain plug. Then align and replace the plug. Screw it in
by hand, but finish tightening it with your wrench. Tighten the oil plug to the
proper torque recommended in the owner’s manual to prevent under- or overtightening.
6) Add Clean Oil
a) On the top of the engine you will find a cap that says "Oil." Unscrew the cap
and proceed to fill the engine with the required quantity of oil, checking with
the dipstick to assure proper fill level. Use a funnel to pour the new oil into the
filler hole on top of the engine (oil spilled onto the engine or exhaust system
will stink up the engine; oil spilled onto the exhaust system can even
potentially be ignited). Then replace the cap and wipe off any spillage. The oil
light should go out as soon as the engine is started. Run the engine for
several minutes, then switch it off and check the dipstick once again to
assure proper oil level. Last, but not least, check under the vehicle for leaks.
B. Automotive Radiators
1) A vehicle radiator and cooling system needs to be clean to be cool. As time goes on,
your car's radiator builds solid deposits that can clog the cooling system. A quick,
inexpensive radiator flush can keep the system in shape. It's important to change
your antifreeze seasonally.
2) Before you start your radiator flush, make sure you have everything you need.
There's nothing worse than draining your radiator only to realize that you need to
drive to the auto store for something!
3) What you'll need to perform a radiator flush:
a) Phillips head screwdriver or wrench (whichever your radiator drain requires)
b) Cloth rag
Maintenance Positions Study Guide 21. c)
Radiator Flush solution
Used coolant receptacle
4) *Be sure to let your engine cool completely before you loosen or remove the
radiator cap. Hot coolant can be painful!
5) Performing the Flush
a) The first step in your radiator and cooling system flush is to drain the old coolant
from the radiator.
1) Using your owner's manual or your eyeballs, locate your radiator's drain plug.
It could be anywhere along the bottom of the radiator, and will be either a
screw plug, bolt plug or a petcock (simple drain valve). Be sure you have your
used coolant receptacle in place under the drain before you open it up.
2) With your coolant catcher underneath the drain, unscrew it and let the coolant
empty completely. If you have a screw or bolt type radiator drain plug,
remove it completely. If your radiator has a petcock, open it all the way.
*IMPORTANT: Coolant can be very dangerous to pets. It tastes sweet to them but
ingesting it can be fatal. Be sure not to leave any -- even a small puddle -- where an
animal could drink it.
a) Once all of the coolant has drained from the radiator, replace the drain
plug and remove the radiator cap. Add the contents of the radiator flush
solution to the radiator, and then fill it to the top with water.
b) Replace and tighten the radiator cap. Now start the car and let it run until
it gets to its operating temperature (the place on the temp gauge that it
normally stays at).
c) Turn your heater on and move the temperature control to the hottest
position. Let the car run for 10 minutes with the heater on.
d) Turn the car off and wait for the engine to cool off. If the radiator cap or
metal radiator is hot to the touch, it's still too hot to open.
*IMPORTANT SAFETY REMINDER: Do not attempt to loosen or remove the radiator cap
while the engine is hot. Serious injury can result! Your cooling system is hot!
e) Once the engine has cooled down, open the drain and completely empty
the contents of the radiator. Your radiator flush is almost finished!
f) Depending on the size of your coolant receptacle and cooling system, you
might have to empty it into a separate container to make room for the
second draining. No matter what, never pour coolant on the ground!
g) Now that you have performed a radiator and cooling system flush, all you
need to do is refill the radiator with fresh coolant.
h) Replace the radiator drain plug or fully close the petcock.
i) Using a funnel to eliminate spills, fill the radiator with a 50/50 mixture of
coolant and water. With the radiator filled, go ahead and fill the plastic
coolant reservoir if your car has separate openings, again with a 50/50
j) Tighten all of your caps well.
Maintenance Positions Study Guide 22. k) It's a good idea to check your radiator coolant level in a day or so to be
sure it's proper, sometimes an air bubble works its way out and you need
to add a little.
C. Automotive Tire Changing
1) Whenever changing a rear tire on a vehicle, it is required that the vehicle is in Park,
the parking brake is engaged and the opposite side front tire is chocked.
a) Jack up the Car
1) The first step is to find your car's spare tire, jack and tire iron. The spare tire
is almost always located underneath the floor mat in the trunk. Unless, of
course, your car doesn't have a trunk. If you own an SUV, minivan or pickup,
the spare tire is often mounted on the back of the tailgate or underneath the
vehicle itself.
2) Once you have found the spare tire, remove it from the car. If you have an air
pressure gauge handy, you will want to check the spare tire's pressure. If this
tire is flat, too, you're in a bit of trouble. But let's just assume you have been
keeping tabs on the spare tire's health, and its air pressure is perfect.
3) The next step will involve removing the flat tire. Make sure that the car is in
gear (or in "park" if the car is an automatic) and the emergency brake is set.
The car should be parked on a flat piece of pavement. Do not attempt to
change a flat if the car is on a slope or if it is sitting on dirt. It's also a good
idea to block the tire opposite of the flat tire. Therefore, if the left front tire is
flat, it would be a good idea to place a brick or other large, heavy object
behind the right rear tire. Blocking the tire makes the car less likely to move
when you are raising it.
4) Use the tire iron (the L-shaped bar that fits over the wheel lugs) to loosen
each wheel lug. The wheel lugs are almost certainly very tight. You'll have to
use brute force. You loosen them by turning them counterclockwise, by the
5) Now, at this point, you don't want to actually remove the lugs. You just want
them loose. Once you have accomplished this, move the jack underneath the
car. If you don't know where the proper jacking points are, look them up in the
owner's manual (you keep your owner's manual in your car, right?).
6) Maneuver the jack underneath the jack point and start to raise the jack. Most
car jacks these days are a screw-type scissor jack, which means you simply
turn the knob at the end of the jack using the provided metal hand crank.
Raise the jack until it contacts the car's frame and continue expanding the
b) Remove the Flat and Install the Spare
1) Raise the car with the jack until the flat tire is completely raised off the
ground. Once this is done, remove the wheel lugs completely. Depending on
how tight the lugs are you might be able to remove them by hand. Set the
lugs aside in a secure location where they can't roll away.
2) Position the spare tire over the wheel studs. This is the most physically
challenging part of the whole process. You'll have to hold up the tire and try
to line up the holes in the wheel with the protruding wheel studs located on
Maintenance Positions Study Guide 23. 3)
the brake hub. One trick that might help is to balance the tire on your foot
while you move it into position.
After you have the spare tire hanging on the wheel studs, screw each of the
wheel lugs back on. You'll want to start them by hand. Make sure you do not
cross-thread them. The lugs should screw on easily. Once each of them is
snug and you can't tighten them any further by hand, use the tire iron to finish
the job. At this point, you don't need to get the lugs super tight. You just want
them snug for now. Make sure that the wheel is fitting flush against the brake
Once the spare tire is on, carefully lower the jack. Pull the jack away from the
vehicle. The final step is to tighten down the lugs completely. The reason you
tighten the lugs now is that the tire is on the ground and it won't rotate around
like it would if it was still hanging in the air.
Wheel lugs have a specific torque rating that they are supposed to be
tightened down to, but there is pretty much no way you can figure that out
using a simple tire iron. The general rule here is to tighten down the lugs as
much as possible.
That's it. Put the flat tire in the space where the spare tire was and put the
jack and tire iron back in the car. Most compact spare tires are smaller than
regular tires , so it is possible that the flat tire won't fit in the spare tire well.
Also, compact spares have a limited top speed. The tire's top speed will be
written on its sidewall. If your vehicle has a full-size spare, you won't
encounter these problems. With the spare installed, you should be able to
reach your house or the nearest service station.
Maintenance Positions Study Guide 24. 4. Building Construction
A. Paint Brushes
1) Painting Tools Overview
a) Although it might seem that you could use any paint brush to paint with, the
brush you choose can be as important as the project itself. It doesn't make much
sense to buy a top quality paint, and then apply it with a really cheap paint brush
or roller. The quality of the results you achieve will be much better with a top
quality paint brush. A great paint brush will hold more paint, give you more
control, provide a smoother finish with fewer brush strokes and will save you
time. As with anything, you get what you pay for when it comes to paint brushes.
The main differences in paint brushes will be the bristle types, the taper, bristle
flagging or splitting, bristle density, the ferrule and balance.
2) Bristle types
a) There are many different types of bristles. Hog hair (or china bristle), polyester,
nylon and blends. China bristle is actually hog hair. It is the best when using oilbased paint because the hog hair is stiff enough for control but soft and naturally
splits at the ends for a very smooth application. Hog hair cannot be used for
water-based paints however because the bristles absorb water. Polyester bristles
are generally stiff. These bristles provide good control but often are too stiff for a
smooth application. Nylon bristles are very soft, which make for very smooth
application but are too flimsy for control. The best synthetic brushes contain a
blend of polyester and nylon bristles. The polyester provide the stiffness for
control while the nylon bristles provide the softness for a very smooth application.
Varying quality of the filaments will also affect how well the paint flows off the
bristle (called the "release").
3) Taper
a) A good brush will taper so that the brush is actually thicker at the bottom and
narrower at the top. This shape gives the brush more stiffness and control. A
cheap brush will generally have bristles of all the same length. A good quality
brush will have a finer tapered edge and longer bristles than the cheaper kinds.
4) Bristle flagging
a) Flagging, or split ends, is what you see at the tips of the bristles. Flagging is
when the bristles are scored or split at the end to provide finer and smoother
application. Great paint brushes have flagged or split bristles whereas a cheap
paint brush will not.
5) Bristle density
a) The more bristles a paint brush has the better (too a point). Paint is held in the
space between the bristles, so more bristles will hold more paint. This allows the
paint to flow from the brush, giving you more control, smoother application and
longer time for holding your line. You'll achieve a straighter and cleaner edge and
spend less time filling your brush and more time painting. A cheaper paint brush
won't hold much paint and therefore is more or less smearing the paint rather
than flowing the paint onto the surface.
Maintenance Positions Study Guide 25. 6) Ferrule
a) The ferrule is the area of the brush that holds the bristles against the handle.
Ferrules are commonly metal and are either square or rounded. Good paint
brushes will have either a stainless steel or other rust-proof ferrule whereas a
cheap brush will use a lower quality metal that is more subject to rusting. The
shape of the ferrule will have an impact on the shape of the bristles. It isn't
necessarily important whether it is square or rounded, and often is just a matter
of personal preference.
7) Balance
a) Most handles are made of rubber or wood. What you want in paint brushes is a
balanced brush that feels comfortable in your hand and is easy to control.
8) The Right Size
a) Your surface will determine what type of brush you use. If you have a wide
surface you will want to use one of the larger 3-4 inch brushes. If you need to
trim around paneled doors you will want a smaller 1½-2" brush. The most popular
brush size is a 2-inch angled sash brush because it is comfortable to use and
hold and can be used to trim around tight areas.
9) Paint rollers
a) The paint roller is your best friend when it comes to painting. Rollers help you
cover a very large surface area in a relatively short time. A good roller sleeve will
hold a large amount of paint and release it onto the wall with minimal splattering
and minimal lint. Nine inch is the most popular roller width. 3/8-inch is the most
common nap length, but 5/16-inch and 1/2-inch are also commonly used. The
best nap length will depend on your wall smoothness and the sheen of the paint
you are using. 1/4-inch or 3/16-inch is the best nap for semi-gloss paint on a
smooth surface, 3/8-inch or 5/16-inch is most common for smooth walls and
matte or eggshell paint, 1/2-inch nap would be used for medium surfaces and
3/4-inch or longer would be used for rough surfaces such as concrete block.
10) Roller Handles and Trays
a) The right paint roller handle is very important. Most people think they can just use
the cheapest roller handle made with thinner gauge steel. The thinner gauge
causes two problems: first, the pressure is only distributed across the roller
sleeve on a couple inches closest to the handle. A good quality roller handle will
distribute the pressure evenly across the whole nine-inch roller cover, so you are
painting with 2 to 3 times more surface area with a good roller handle than a
cheap roller handle. Second, the thin gauge doesn't provide enough tension to
adequately keep the roller sleeve on the handle, so the sleeve will spin itself off
the cage while you paint and you'll find yourself every few minutes trying to put it
back on - this is very annoying and time consuming. A good roller handle has
special locks that keep the roller cover firmly in place on the handle.
b) A roller tray will also be necessary. You'll want to choose a tray that holds a good
amount of paint and can be used with disposable liners.
11) Painting Tapes
a) Blue painting tape is used to mask any area you don't want covered with paint.
Use it to edge along the ceiling or wall prior to painting, around door and window
trim and on any hardware or fixtures you don't want painting. Taking a little extra
Maintenance Positions Study Guide 26. time preparing the area before painting can ensure great results. There are two
main types of blue painting tape: crepe paper and rice paper. Crepe paper tape
is less expensive, but is thicker and not as smooth. Riced paper tapes are thinner
and much smoother. They give the most crisp lines but are more expensive.
12) Drop cloths
a) A drop cloth is used to protect floors and furniture from paint drips, splatters and
spills. Heavy Duty Canvas is best for walking on or anywhere paint can spill.
Plastic sheeting is best for covering furniture or anything else against splatters.
13) Preparing the Brush
a) Before painting, dip the brush into water if it will be used with latex paint or into
mineral spirits if it will be used with oil paint. Dab it dry with a clean rag. This step
will help keep the paint from crusting under the ferrule. If paint should dry against
or behind the ferrule, the brush will be useless for painting because the bristles
will be clumped — like a club — and the reservoirs to hold paint between the
bristles will be destroyed.
14) Position the Brush
a) Holding a paintbrush correctly not only reduces hand fatigue but helps to control
the brush stroke and dispenses the paint smoothly. It also extends the life of the
b) Painters with large hands often hold all their brushes like a pencil with the ferrule
between the thumb and forefinger. Those with small hands often find they can do
this only with their small brushes. Large three- to four-inch wide brushes are
often held with all fingers on the ferrule and the crook of the thumb around the
handle and the tip of thumb on the underside of the ferrule.
c) The paintbrush should feel balanced. Hold it at a 45º angle to the surface. By
holding it with your hand toward the base of the handle you improve control and
prevent spatter. It will also help to relieve repetitive injury to your wrist.
d) If the handle feels uncomfortable, experiment by covering it with layers of duct
tape or spongy pipe insulation.
15) Using the Brush
a) Don’t waste time lapping the dipped brush against the paint can rim to remove
excess paint. Instead pour a few inches of paint from the original container into a
clean paint can and dip the brush into the paint — dip one-third to one-half the
length of the bristles into the paint. Raise it out and tap both sides of the brush
against the inside of the can. Rather then having paint running off of the brush
into the can rim and down the sides of the can, it flows back into the painting can.
Tapping the brush also forces paint between the bristles where it is stored until
the brush touches the painting surface.
b) In a small area no more than two by three feet, begin painting in a back and forth
method, from one side of the brush to the other. Force the brush against the
surface just hard enough to slightly flex the bristles. Tip off, or feather the edges
of the painted area. This is done by brushing out on the final stroke with the tips
of the bristles and lightly pulling the brush off the surface. By feathering off on the
stroke there will not be paint build up on the next stroke. Paint from the dry area
Maintenance Positions Study Guide 27. back to the previous wet stroke (area just feathered) to further avoid lap marks
caused by paint build-up.
c) Never paint with the side of the brush because it splays the bristles and makes it
difficult to maintain a clean edge.
16) Cleaning Brushes
a) Start cleaning the brush by swiping it back and forth across some newspaper.
b) For latex paint: Rinse the brush under running tepid to warm water making sure
to have the water running down the handle, through the bristles. Holding the
brush incorrectly with the water running from the bristles toward the handle traps
any paint debris in the ferrule causing the bristles to separate. Use a wire brush
or brush comb to remove any dried bits of paint. Rub a drop or two of dish soap
into the bristles and rinse under running water.
c) If the latex paint is extremely tacky and difficult to remove, dip the brush into a
solution of a quarter-cup of fabric softener to a half-gallon of warm water. Divide
the mixture into two containers. Swish the brush around for a minute in the first
container. The fabric softener is a wetting agent, which reduces the surface
tension of the water, helping the water to dissolve the paint. Rinse the brush in
the second container.
d) For oil paint: Select several containers with lids that are big enough to hold the
dirty brush suspended in the container filled halfway with mineral spirits. Use the
hole in the paint handle to tie the paintbrush to a paint stick or ruler laid across
the container of solvent. Soaking the brush for five to ten minutes softens the
paint and makes it easier to clean. Wearing plastic gloves, use a wire brush or
brush comb to remove any dry paint particles Move to the next container of
solvent and flex the bristles so the solvent reaches into the ferrule. When the
solvent turns cloudy, move to the last container of solvent as a final rinse.
e) Be sure to mark all the solvent containers as “Poison Mineral Spirits.” The paint
residue will settle to the bottom and the solvent can be poured off and used over
and over. Keep the lids on tightly and store away from heat or flames.
f) Wipe the clean brushes on newspaper to remove excess water or solvent. Then
spin them by hand or with a mechanical brush spinner. Do this over an empty
bucket or trashcan to collect the spray.
g) Wrap the dry brushes back in their original cardboard sleeves or make a sleeve
out of the paper from a double-strength grocery sack. Secure the paper with
tape. Label the sleeve with the size of the brush and if it is for oil or latex. Store
the brushes by hanging them by the hole drilled in their handles.
h) For a short break in painting, as long as overnight, don’t bother cleaning the
brush; simply put the entire brush into a plastic bag, seal it, and put it in the
refrigerator. Some do-it-yourselfers put their brushes in the freezer but this is a
bad idea because the freeze-thaw cycle destroys the paint on the brush — in
effect — and gums up the first few strokes. If the brush has a wooden handle it
can crack, and if it has nylon bristles they will become brittle and break.
i) The worst thing you can do with a dirty paintbrush — short of tossing it into the
trash — is to stand it in a container of water or mineral spirits to prevent it from
drying out. Standing a brush on its bristles will distort the bristles — think of a bad
hair day or a cowlick — and the brush will not be usable for painting a clean
j) Finally, don’t think cleaning the brush is something that occurs only at the end of
painting. If the brush should start to feel stiff and the bristles seem to be
saturated, gummy, or unresponsive, stop and clean the brush. Professional
Maintenance Positions Study Guide 28. painters will often clean their brushes every two hours to make sure they leave a
smooth, not grainy, surface behind.
k) The well-maintained brush will lay down a thick film of paint, improving the hiding
power of the paint. And because a good brush means no thick and thin spots in
coverage, the painted surface should wear uniformly. With the absence of brush
marks, the sheen will be uniform and the surface will not collect as much grease
and grime.
B. Framing/Drywall
1) Plan Your Project
a) Measuring: Using a tape measure, determine the dimensions of the existing
space as well as the lengths of your new walls. It is a good idea to plot those
dimensions on grid paper (1square=1foot) so that you have a top view of the
project. Mark the wall dimensions on your drawing.
b) Stud Spacing: Space the studs 12”, 16” or 24” on center. Note allowable wall
height table below.
c) Number of Studs: Based on spacing requirements, divide the wall length by 1
(12” o.c.), 1.3 (16” o.c.) or 2 (24” o.c.) to figure the number of studs needed. Add
one more stud for each corner.
d) Number of Track Sections: Multiply the total lineal feet of wall by 2 to figure the
amount of track needed for floor and ceiling runners. Track is sold in 10’ lengths
and may need to be cut per wall.
2) Tools
a) Reversible Drill or Screw gun for installing or removing fasteners, and should
have clutch to stop over penetration of fastener.
b) Tin Snips – for trimming studs/track.
c) Plumb Line – for aligning floor track with ceiling track.
d) Measuring Tape – for measuring lengths and distances
e) Framing Square – for square-cutting studs and track
f) Level – for checking vertical/horizontal alignment
g) C-Clamps or Open-Frame Locking Pliers – for holding unattached studs/track
securely when fastening with screwgun.
3) Safety Warning
a) Eye protection is required to safeguard against metal pieces and particles
produced while cutting or screwing metal components.
b) Safety goggles or glasses are recommended.
c) Leather-palm Gloves are recommended to protect against sharp edges or
4) Drywall Tools
a) Square
b) Utility Knife or Drywall Saw
c) Rasp
d) Joint Compound
e) Paper Joint Tape
f) Joint Knives
g) Top Runner (Track)
Maintenance Positions Study Guide 29. h) Metal Wall Stud
i) Plastic Grommet
j) Bottom Runner (Track)
5) Instructions
a) Cut studs/runners to required lengths as you install using aviator snips or
circular saw with abrasive, metal-cutting blade.
b) Attach ceiling runner. Use drywall screws to attach to joists. For parallel
joists, bridge two joists with C-runners spaced 24” o.c. or less and install
ceiling runner across bridges. Use expandable fasteners in the field of an
existing ceiling. Space fasteners 12”-16” on center (2” from ends of runner).
c) Plum to position floor runner directly below ceiling runner.
d) Attach floor runner. Use powder-actuated fasteners for concrete floor. Use
drywall screws for wood subfloor. Same fastener spacing as ceiling runner.
Then mark stud locations 16” or 24” o.c. top and bottom starting from the
same end.
e) Insert stud at slight angle into runners–then twist into place. Be sure all stud
legs are pointed the same way for easier drywall attachment and punchouts
are oriented the same way for easy plumbing or electrical installation.
f) Screw-attach stud to ceiling runner and floor runner with 7/16” pan or waferhead screws. Hold stud flange to runner for easier screw attachment.
Attachment of drywall will hold studs in alignment.
g) Cut tabs approximately 4” long for attaching door header and stud bracing.
Tabs may be bent either up or down.
h) Attach C-Runner bracing across studs to support cabinet attachment. CRunner must be notched to fit between studs.
i) Insert grommets or pieces of pipe insulation into pre-punched holes
whenever you pass through wiring and/or plumbing. Your framing is now
complete and ready for installing the drywall.
LIMITATIONS: 25-gauge Steel Studs are designed for use in nonload-bearing
construction only. Check local building codes before beginning construction.
6) Tips
a) The flange on a steel stud is flexible and may deflect when you’re trying to
pierce it with a drywall screw, especially when two panel edges meet on a
single stud. To prevent this, secure the first panel to the open side of the stud
(the one that’s opposite the web)—to give it rigidity—and then hang the
second panel. Grip the back of the stud flange near the screw connection
point with your fingers (to give it support) and then drive the screw.
b) Levels with one magnetic side are helpful when working with steel studs.
c) Some people find it well worth the little extra money to use 20 gauge studs
rather than the usual 25 gauge ones. The walls feel more solid and the cost
difference typically isn't all that much.
d) Use common sense when doing any type of work. If you are extremely tired,
or rushing, you may hurt yourself.
e) Self-tapping screws make joining pieces much easier.
f) Don’t try nailing trim into steel studs. It will not hold. Instead, use specially
designed trim screws for the job.
g) Cut steel is sharp - wear gloves.
Maintenance Positions Study Guide 30. h) Wear eye protection when cutting steel and when driving screws. It's not
unheard of for a screw to jump off the power screwdriver and shoot out at
you. Once it happens once, you'll appreciate your safety glasses.
7) Drywall
a) Drywall typically comes in 4'x8' sheets and is normally installed horizontally
but can be installed vertically if desired. Larger 4'x12' sheets are available
however they are hard to work with unless you are a professional with a few
extra hands. These larger sheets tend to break easily during transport to the
job site but are great because the larger sheets mean fewer joints to tape.
b) Thicknesses range from 1/4" - 5/8" with 1/2" being the most popular. The 1/4"
sheets are often used as overlays to existing drywall and are not intended to
be used in new construction. Check your local building code for requirements
in your area.
c) Composition is another factor when selecting drywall as there are various
moisture resistant products commonly called 'green rock' designed for
installation in high moisture areas such as garages and bathrooms. Check
your local building supply store before committing to purchase. Green rocking
the whole house may be overkill but is great because of it's moisture resistant
d) Prepare the wall for your new drywall by removing all old drywall, nails,
screws and anything else that will prevent the new drywall sheets from laying
flat on the studs.
e) Now is a good time to inspect and repair hidden damage such as loose
blocking, moisture damage, termites, etc. Don't be surprised to find steel
studs instead of wood. This is really a good thing since steel has many good
qualities such as added strength, termite-proof, and fire retardant. The only
difference is that you have to use drywall screws instead of nails, and that is
better anyway.
f) Inspect insulation that is stapled to the studs. Use Kraft tape to repair tears in
the paper backing to maximize your energy efficiency.
g) Use triple expanding foam to seal cracks and gaps on exterior walls.
h) Be advised that drywall has a mud cavity along the length wise seams to give
the mud a place to adhere without forming a mound that will be unsightly on
your finished wall.
i) Measure the wall where you would like to install drywall. Most likely you will
have to cut some pieces. When cutting drywall, use a razor knife and score a
line on one side of the drywall paper. Place your knee on the opposite side of
the cut and quickly pull the drywall piece towards you while at the same time
pushing your knee outward to snap the drywall in a clean line. Then simply
use your razor knife to cut the remaining paper along the newly formed
j) Cut the pieces being very carefully, because the knife or saw that you use
always somehow seems to want to go off the line. I recommend using a
straight edge as a guide for the razor knife. Remember that you don't have to
press any harder than required to cut one side of the paper since you will
snap the drywall along your cut line.
k) Use a hand drywall saw to make cuts along irregular openings such as
l) A good practice when installing drywall over protruding pipes is to place the
drywall against the pipe and lightly tap with a flat block of wood to dimple the
Maintenance Positions Study Guide 31. back, then pull the drywall away and use a drywall circle cutter or drywall hole
saw and cut a perfect hole that should be much easier to finish out than if you
punch out a large hole that requires 3-4 coats of mud to finish.
m) Locate the studs with a stud finder if they are not visible. Don't trust that your
studs will all be on 16" or 24" centers. A good idea is to run a length of
masking tape along the floor while you have the studs exposed and mark the
center line of each stud with a high visibility marker.
n) Make sure to use a spring loaded drywall screw dimpler since they are
designed to automatically countersink each drywall screw to precisely the
same depth before ratcheting the screw bit as a sign to quit and back off the
o) Have someone help you hold the drywall on the wall, and use the drill to
install the screws in at approx 8" centers on the vertical studs. Extra screws
may help in some situations however they are usually overkill and will require
extra mudding and sanding that will detracting on the overall finish.
p) When possible, install the screws closer to the edges that will be trimmed so
that the screw heads will be covered by baseboard or door frame trim.
q) Use at least a 6" drywall knife to apply a liberal amount of mud to each seam.
r) Have your drywall tape pre-cut and lightly dampened with clean water. Don't
need to soak it down too much.
s) Recommend avoiding the perforated and fiber tapes as they don't produce a
flawless finish and require gobs of extra mud and sanding to get the job done
t) Put drywall tape over the joint you just applied the mud, then use your 6" or
8" drywall putty knife to flatten the tape by starting at one end and pulling
towards you to the other end in one smooth motion.
to clean your blade after each swipe to ensure a professional finish. Dip it in
water in between each swipe and wipe it on the mud tray edge to ensure a
clean application. The putty knife will collect small dust particles that will
cause streaks in your finish which is why you will want to discard the excess
mud after each swipe.
v) Inspect your recently taped joint for air bubbles. Wet your blade and flatten
them out with another swipe if needed.
w) Repeat for each joint until all joints are taped.
x) Don't apply any mud over freshly taped joints! Allow them to thoroughly dry
for one day between coats unless you are using hot mud that will dry in an
hour. A great idea is to use pink mud that dries white indicating it is ready for
another coat.
y) For corner beads you may want to use a corner tool that is available for both
inside and outside corners to give your job a professional finish.
z) Apply at least 2-3 more coats using a slightly wider putty knife for each
application letting it dry between each coat. It will bubble if you rush it!
aa) Don't forget to apply a swipe coat over each screw. You shouldn't notice any
edges after screeding the mud over a joint line or screw dimple. Make sure to
hold the blade flat against the drywall and pull towards you in smooth but firm
strokes. Practice on an old piece of drywall to refine your technique.
bb) Also screed some mud over any small imperfections in the drywall that may
occur during installation such as missed nail/screw holes.
cc) Many thin coats of mud will give you better results but patience is required to
let it dry.
Maintenance Positions Study Guide 32. dd) Use a pole sander with drywall sand paper to sand the joints after the final
coat has dried. Don't get carried away and sand until you expose the paper.
This step goes quickly because the mud will sand off easily.
ee) Contrary to urban legend, you don't have to sand everything such as mud
over screws or nails if you created a smooth screed of mud when you put on
your top coat.
ff) Drywall breaks very easily, so when you carry it, don't let the middle bow
down too much.
8) How to Tape and Mud Drywall
a) Know that drywall board comes in a variety of sizes, types and widths.
1) Typically walls are covered in 1/2 or 5/8 inch thick drywall board bought in
4x8 or 4x12 foot sheets. There are also many different specialty products on
the market, such as larger 4x16 sheets, specialty ceiling boards called "CV"
boards that are more resistant to sagging, and there are sheets that are
54"x8 or 12' for specialty applications such as 9' ceilings.
b) If you find you need to cover walls that are in poor shape and past the typical
amount of repair, you can also get 1/4 inch drywall sheets, but they may be as or
more expensive than regular thicknesses.
1) Ceilings and walls unless as regulated by specific fire codes are usually
covered in 1/2" drywall sheets. In ceilings you usually use "CV" rated or
ceiling boards. In some instances you may be required to place 5/8" drywall
on your ceilings or outside walls, 5/8" drywall is usually classified as "Firerated" drywall and stands up to fires longer than traditional 1/2" drywall does.
A special lift (easy to rent) can hold these large sheets against the ceiling
while you attach them.
2) A 'drywall lift' can also be made using 2 x 4s nailed into a T-shape that is
placed under the dry wall to hold it against the ceiling as you place a few
screws into the panel to secure it. However, if you are installing drywall on
your own or don't think you have the upper body strength to manipulate the
drywall, a lift is well worth considering renting.33
c) Drywall that will be installed in wet locations is called green board or MR board
meaning moisture resistant (for example, behind bathroom tile) must be the type
that can withstand water. Usually these sheets are covered in green paper, not
the usual gray.
1) Drywall should not be used for tub surrounds or showers. The correct
material would be cement board with an 8 mil vapor barrier behind it. The
seams of the cement board need to be finished with a fiberglass mesh tape
which is then covered with a "setting type" joint compound or "thin set" tile
d) Drywall that is to be installed in areas where fire is a concern, for example
around a water heater enclosure, is required to be much thicker.
1) In some municipalities you can double your drywall in fire risk areas, rather
than buy far more expensive thicker sheets.
2) Check your local planning department and municipal building codes for
drywall rules and regulations in your area.
e) Check that the drywall is attached to the wall studs correctly.
1) Wall drywall should be screwed to all the studs it covers every six to eight
inches. Ideally, it should be supported at each edge and every 12 inches in
the middle of the panel in a wall framed 24 inches on center, giving you top to
bottom 5 screws; in a more usual wall with studs on 16 inch centers, you will
Maintenance Positions Study Guide 33. have a row of screws on each edge plus two rows spaced 16 inches in from
each edge.
f) Drywall screws must be correctly countersunk. Invest in a counter-sinker
designed for drywall applications. This tool attaches to the end of your drill and
perfectly countersinks every screw you place.
1) Run the blade of your trowel over the screws to make sure none are sticking
out. Remove, countersink or otherwise deal with any screws that are sticking
out even a little bit. You want the screws to dimple but not tear the paper
coating of the drywall.
2) Do not use drywall nails unless you have been hanging drywall for years as a
professional. The chances of a nail bending, putting your hammer through the
drywall or simply an incorrect countersink on the nail head are great. Drywall
screws are far easier to work with, but you will need a power screwdriver.
g) Drywall boards should meet at chamfered edges only and be no more than 1/8 to
1/4 inches apart.
1) If two pieces of board do not meet at a chamfered edge you can use a utility
knife to cut a rough chamfer all the way down the edge if you have a steady
hand. If not, you will have to adjust the seam to accommodate the difference
in thicknesses, placing the bulk of the mud on the chamfered side.
h) If your local municipality requires an inspection before mudding your drywall,
schedule the inspection.
i) Begin with the tape coat
j) Buy ready-mixed mud and make your life much easier in one single step!
1) Do not use Spackle. Mud is not Spackle, it has no "glue like" quality.
2) Don't dilute or mess around with the mud mixture. You can do so, but there is
no reason to in the vast majority of applications. Spackle is intended primarily
to patch nail and other holes in drywall.
3) There are several brands and grades of mud. Use the "all purpose" mud for
your base (first) coat to seat or cover the tape, and light mud for the final
coat. You can also use what is called brown or topping mud; it's actually
beige and dries to a very pale color, and has a more plastic texture than
regular mud. It dries smoother, has less of a tendency to bubble, and is
intended for the final top coat.
4) You can buy mud in square plastic boxes, or in tubs. It's cheaper in the
boxes, if that is an issue. Try getting one tub and then boxes and use the tub
with the mud from the boxes when it is empty. or use another clean plastic
container that is easy to handle.
5) Stir the mud a little, but not too much. Stirring ready-mixed mud can introduce
air bubbles that will result in an uneven finish.
k) Using a trowel
1) Plastic knives (trowels) intended for use on walls have a tendency to get
burrs on their edges over time, so check if you are using plastic tools to see
that they have smooth edges. Metal knives can rust, so make sure to clean
them well at the end of your work session and dry them carefully.
2) Place a generous amount of mud onto your knife.
3) Press the mud into the seam between the drywall boards.
4) You only need to press hard enough to fill the seam and leave smooth mud
on the wall. The chamfered edge on a sheet of drywall tapers from about 2.5
inches to the edge, so you want to cover the entire six inches of drywall from
edge of the chamfer on one sheet to the edge of the chamfer on the other.
Maintenance Positions Study Guide 34. Use a bright light held at an angle to better see the chamfer area that must be
5) When using the wide blades loaded with mud the best bet is to place the
loaded blade perpendicular to the wall, at a 45° angle. As you draw the mud
and blade down the wall sharpen the angle until the blade and the wall are
almost flat together.
6) Leave plenty of mud on the wall, at least three inches on each side.
l) Cut the paper drywall tape to the correct length, with a little extra on each end.
1) Some people recommend soaking the tape in water first. While this may
make it a little easier to work with it greatly increases the mess and
awkwardness of the tape when actually mudding.
2) Only use plastic, mesh or specialized tapes for their specific applications.
They can be harder to work with and may require three, four or more coats of
mud. If you are doing inside or outside corners, for example, mesh tape is not
the best choice as the tape is not intended to fold. If you are careful mudding,
you can use mesh tape on seams with two coats, but you may find that you
spend more time getting a good final coat.
m) Press the tape into the freshly mudded wall with your hands.
1) Be sure the center of the tape is as even as possible with the seam between
the drywall boards.
2) Clean your knife. Pay attention to the back as well as the front of your knife;
when you are using the knife on the wall, if you see streaks pulled in the mud,
you may have a bit of dried mud or something else on the back of your tool.
3) Pressing as hard as practicable (you don't need to break your knife doing
this, but you still want to press most of the mud out from under that tape), pull
the knife along the seam removing extra mud as you go.
4) The goal at this stage is to get mud into the tape, not finish the job.
5) If your tape starts to buckle simply flatten it out with your hand.
6) Be sure all parts of the seam and tape are mudded.
n) Once all the tape is covered in mud use a wide knife to smooth out and remove
as much of the extra mud as possible.
1) At this stage you are not going for perfection. It doesn't have to be super
smooth. The important thing is to make sure the tape is covered in mud and
correctly positioned in the seam. However, try not to have a large hump over
the seam, or high edges. These will require sanding out later.
o) Leave this to dry. Overnight is best.
1) While waiting, fill the screw holes with mud using your palette knife. Just
apply some mud and then take it all away again, if you countersunk your
screws properly you should have a small dot the size of a screw head of mud
without seeing your screwhead. If you leave lines of mud behind while doing
this all you're doing is creating more sanding for yourself later. Mud shrinks
as it looses moisture, so you may have coat these 2 or 3 times, although
small cracks can just be filled with paint.
9) Corners
a) Corner seams require special attention. You will need to use a 45° knife while
working in the corners.
b) Fill the corner seam with mud and, once again, leave some mud on the wall.
c) Cut the tape to the right length.
d) Fold the tape down the middle. You will find a crease there to make this easier.
e) Push the tape into the corner seam as neatly as possible.
Maintenance Positions Study Guide 35. 1) Often the tape will "disappear" into the corner seam. Your goal is to make the
nicest 90 degree angle possible, and this is controlled by the tape, so pull it
out and start over.
2) Once the tape is in place in the mud, mud over it again using your 45° mud
3) Carefully remove any extra mud from the corner and walls.
10) Outside corners
a) Outside corners do not use tape, rather they use a metal corner strip. You can
also buy plastic or fiberglass corner bead although this is difficult to work with.
b) Cut the corner strip to the right length using tin snips. Be careful not to bend the
corners out.
c) Nail or screw the corner strip to the wall.
d) Load plenty of mud onto the 6 inch knife.
e) Pull the mud down the wall, one part of the blade resting on the metal and the
other on the drywall.
f) Make it as smooth as you can and leave to dry.
g) Corners typically take two coats to cover the metal, but remember that your paint
will also cover some of the metal.
11) The second coat
a) Run your dry clean blade over yesterdays work, rubbing away obvious burrs and
1) Use a larger blade, 8 to 12 inches in width.
2) Understand that the goal of this coat is a smooth finish, not filling anything in,
so take time and care.
b) Load your blade with mud.
c) Pull the mud over the seam a second time.
1) Feather out the mud as smooth as possible to a width of about four to six
inches on either side of the seam, using the knife horizontally rather than
vertically, then go over the body of the seam vertically for a final smoothing.
d) You are done when you can no longer see the tape.
1) The idea of this second coat is to fill up the bevel of the drywall so if you were
to take your drywall knife and place the edge on the seam at a 90 degree
angle you wouldn't see any light between the joint and knife, ideally on the
second coat you should have a small hump in the middle of your seam to
allow for the shrinkage of the mud as it dries.
e) Feather the edges again if necessary.
1) Use quick but hard swipes of the blade to spread the mud out to the thinnest
coat possible.
f) After this coat has dried, inspect your work. Look for pits and holes in the
mud that are too large to be filled with paint to a smooth surface. If you find
such marks, do a third coat, or if the pits and holes are few, fill them to the
surface of the rest of the dried mud.
12) Sanding
a) Do not sand after the first coat; the tape is still too close to the surface and you
risk breaking it.
b) Always sand after the final coat.
c) Sanding during intermediate coats is optional and depends on how smooth you
can get the mud. For very light sands between coats of mud consider a wet sand.
Maintenance Positions Study Guide 36. 1) Find the smoothest surfaced sponge you can and wet it down so it is damp,
not dripping.
2) Rub the sponge over the mud. The sponge will re-wet the surface of the mud,
filling in gaps.
3) Continually clean your sponge.
4) Be very careful not to use too much water or you could dislodge your
previous work.
d) Sand using a sanding block and fine sandpaper, at least 150 grit.
e) You can also use a hand-held "orbital" sander so long as you keep it in constant
f) Seal the room as best you can and wear proper breathing protection.
1) The dust created from sanding gypsum is very fine and unhealthy.
2) Use a shop vacuum to clean up, after having attached a hose to vent outside.
13) Tips
a) After the mud is dry, do not sand. Use a clean trowel and just scrape off the
lumps and bumps.
b) Keep the side of the tub clean by frequently moving the mud off the sides and
corners into the middle. Thin mud will dry quickly forming chunks that will cause
c) Do not use fiberglass tape, it's too expensive and the joints crack easily.
d) Shine a light across the wall, it will show any imperfection.
e) Tape vertical joints before taping horizontal joints. Horizontal tape joints will cover
the ends of the vertical tape.
f) Take your time. It will take two to five coats to get a perfect finish, depending on
your experience, and each coat needs to dry fully.
14) Warnings
a) Do not let dried mud fall back into the tub or bucket. Dried mud stays dry and will
introduce bumps and problems into your work. If you do see lumps in your wall
mud, remove them with your fingers or a trowel before the mud dries, otherwise
you will have to sand them off and start over.
b) Before it dries mud is water soluble, so remove drips and splashes promptly. On
carpet it can work better to leave the mud to dry and then remove it.
C. Building Construction Suspended Ceilings
1) Following are tips and instructions on how to install a
suspended ceiling. Spend a few minutes reading the
directions thoroughly. This can help save you time and
effort. Inside this document you will find information about:
a) Planning for a Suspended Ceiling
b) Installing Wall Angles
c) Locating and Hanging Suspension Wires for Main
d) Installing Main Tees
e) Installing Cross Tees and Border Cross Tees
f) Installing Ceiling Panels
Maintenance Positions Study Guide 37. FIG. 1 ‐ Sketch your room dimensions to scale here. 2) PLANNING FOR A SUSPENDED CEILING
a) First, get the exact measurements of the room where the
suspended ceiling will be installed. Use special care in
measuring any odd-shaped alcoves, bays, etc.
b) Draw the exact dimensions to scale on graph paper (Fig. 1),
or bring the room dimensions to your local retailer and ask
a salesman to assist you in estimating the materials you'll
c) You can choose from either a 2x2 or a 2x4 pattern (Fig. 2).
The pattern you pick will determine the material
requirements for your ceiling.
d) For the 2x4 pattern, decide whether you want to install the
patterns in a standard or reverse pattern (Fig. 3). Each
pattern offers a different appearance.
e) Now that you've made these decisions, sketch the layout
for the planned ceiling on graph paper. You can use the
layout in Fig. 1, or purchase graph paper in a variety or
stationery store. Regardless of which pattern you select,
FIG. 2 ‐ Select the grid pattern you draw the main tees 4' apart. Position the tees so that the want to use.
border patterns at the room edges are equal on both sides
and as large as possible. Try sketching several layouts
before beginning the actual installation to determine which
one looks best.
f) It is important to space the cross tees so the border panels at
the ends of the room are equal and as large as possible. If
you are using a 2'x4' pattern, space the 4' cross tees 2' apart.
For a 2'x2' pattern, add 2' cross tees between the midpoints
of the 4' cross tees (Fig. 2).
g) If the ceiling will be recessed and built-in lighting will be
installed, decide where to locate the panels of light and
clearly identify them on the drawing.
h) The drawing will help you pretty accurately estimate the total
cost of the materials you'll need. Fig. 4 illustrates a basic plan
for estimating costs. Add or delete materials for the job you're
a) Determine the exact height at which the suspended ceiling FIG. 3 ‐ If you're using 2x4 will be installed. Allow a minimum of 3" to 4" clearance panels, choose from either a between the old ceiling and the new ceiling for installation of standard or reversed pattern.
the ceiling panels. If clearance is a problem, you may want
to use fiberglass ceiling panels, which are more flexible.
Additional clearance will be required if you are using
recessed lighting (Fig.5).
b) After locating the exact position for the suspended ceiling,
use a level to draw a line completely around the room
indicating where the wall angle will be applied (Fig. 6). Don't FIG. 5 ‐ Allow a minimum of 6" space assume the original ceiling is level–use a level for accuracy. between the ceilings if you're using Set the wall angle low enough to conceal as many pipes, recessed lights.
Maintenance Positions Study Guide 38. ducts, etc., as possible.
c) Fasten the wall angles securely to the wall at all points.
Nail them firmly to studs, or use screw anchors or other
masonry fasteners on brick or masonry walls (Fig. 7).
d) Position the wall angle so that the bottom flange rests on
FIG. 6 ‐ Use a level to apply the wall the level line you have drawn on the wall. Take the time to
angle at a proper height around the do this right!
e) Overlap the wall angle on inside corners (A, Fig. 8), and
miter the wall angle on outside corners (B, Fig. 8). Make a
temporary wooden miter box if you don't have one. Cut any
needed angles with metal cutting snips or a hacksaw.
a) If you are going to use recessed lights, install the wiring
before putting the suspension wires in place (Fig. 5).
b) For recessed lighting, you can use 2x 2 or 2x 4 drop-in
lighting fixtures, which are specially designed for this
purpose. You can also center fluorescent light fixtures over
the panels and use a luminous lay-in panel instead of a
regular ceiling panel. These lay-in panels now come in
several attractive designs.
c) Refer to your sketch of the room for the location of all main
tees (Fig. 1). Main tees should always run at right angles to
the joists in the room.
d) Locate the position of each main tee by stretching a tight
line from the top edge of the wall angle on all sides of the
room at each position where the main tees are to be placed
(Fig. 9).
e) Now, cut the suspension wires to the proper length. The
wires should be 12" longer than the distance between the old
ceiling and the new guideline string you have stretched to
indicate the position of each main tee.
f) Locate the first suspension wire for each main tee directly
above the point where the first cross tee meets the main
tee. Check your original sketch of the room to determine
this location.
Be sure the suspension wires are securely fastened.
Apply them to the ceiling with screw eyes, screw hooks,
nails, or drilling (Fig. 10).
Attach a suspension wire every 4' along the level
guideline (Fig. 11). Stretch each wire to remove any
kinks and make a 90° bend where the suspension wire
crosses the level line.
Most main tees are 12' long and have cross tee
slots punched every 12" beginning 6" from each end
(Fig. 12).
Refer to your layout sheet to determine the
distance from the wall to the first cross tee. Now
FIG. 7 ‐ Fasten the wall angles securely to the wall at all points
FIG. 8 ‐ Overlap the inside corners and miter the outside corners.
FIG. 9 ‐ Stretch a tight line from the top edge of the wall angle on all sides of the room at each position where the main tees are to be placed.
Figure 10‐ Be sure the suspension wires are securely fastened.
Maintenance Positions Study Guide 39. measure this distance along the top flange of the main tee
and locate the slot just beyond this point.
From this slot, measure back the same distance,
subtract 1/8" and saw the main tee at that point. The 1/8"
subtraction is for the thickness of the wall angle.
If the wall angles are not square, position the cross
tee slots accordingly.
When main tees are installed in rooms less than 12'
across, cut the main tee to the exact measurement of the
room, allowing 1/8" for the thickness of the wall angle (Fig. 13).
For rooms wider than 12', the main tee can be spliced Figure 11 Add a suspension wire every (Fig. 14). Be sure to align the splice so that the suspension 4' along the level line and bend at a wires are correctly positioned. Splice carefully, or all the main 90° angle
tees will be thrown off.
Install the main tees so that they are all level with the
wall angle already mounted. Use a long level for this.
Most main tees are 12' long and have cross tee slots
punched every 12" beginning 6" from each end (Fig. 12).
Refer to your layout sheet to determine the distance
from the wall to the first cross tee. Now measure this Figure 12 Main tees generally have distance along the top flange of the main tee and locate the cross tee slots every 12".
slot just beyond this point.
From this slot, measure back the same distance,
subtract 1/8" and saw the main tee at that point. The 1/8"
subtraction is for the thickness of the wall angle.
If the wall angles are not square, position the cross
tee slots accordingly.
When main tees are installed in rooms less than 12'
across, cut the main tee to the exact measurement of the
room, allowing 1/8" for the thickness of the wall angle (Fig.
Figure 13 If the room is less than 12' f)
For rooms wider than 12', the main tee can be spliced across, cut the main tee to the width (Fig. 14). Be sure to align the splice so that the suspension of the room less 1/8" for the thickness wires are correctly positioned. Splice carefully, or all the main of the wall angle.
tees will be thrown off.
Install the main tees so that they are all level with the wall angle already
mounted. Use a long level for this.
a) Install the cross tees by inserting the ends of the cross tees into
the slots in the main tees (Fig. 15). Use the manufacturer's
instructions for fitting the cross tees into position.
b) Determine the location of the cross tees by the pattern you
selected–either 2'x2' or 2'x4' (Fig. 2).
c) Be sure the lock tab on the cross tee is on the outside of the
slot (Fig. 15). This attachment is slightly different in some
types of tees.
Figure 14 Main tees can be spliced for d) You can remove most cross tees by depressing the lock tab rooms wider than 12'
with a screwdriver.
Maintenance Positions Study Guide 40. e) Border cross tees are installed between the wall angle and the
last main tee.
f) Measure from the last tee to the wall angle, allowing 1/8" for
the thickness of the wall angle. Cut the cross tees and install
them by inserting the connector in the main tee and resting the
cut edge on the wall angle.
a) Your final main and cross tee arrangement will look similar to Fig.
16. The top part of the illustration shows an arrangement of a 2'x4' Figure 15 ‐ Insert the cross tees into layout, while the lower half shows main and cross tees arranged the slots in the main cross tees.
for a 2'x2' layout.
b) Drop the ceiling panels into position by tilting them slightly, lifting
them above the framework and letting them fall into place (Fig.
c) Check your state and local codes before starting any project.
Follow all safety precautions.
Figure 16 Your final tee arrangement will look similar to this.
Figure 17 Tilt the ceiling panels slightly and drop them into position.
Maintenance Positions Study Guide 41. Use Figure 4this as a guide in estimating the costs for your ceiling installation.
Cost per piece
Total cost
______ 12' main beam pieces
@ _______
$ _______
______ main beam splicers
@ _______
$ _______
______ 4' cross tees
@ _______
$ _______
______ 2' cross tees
@ _______
$ _______
______ 12" wall mold
@ _______
$ _______
______ 2x2 ceiling tiles
______ 2x4 ceiling tiles
@ _______
$ _______
@ _______
$ _______
Total cost of ceiling
Maintenance Positions Study Guide $ _______
42. 5. HVAC
A. Belt replacement
1) The best method when replacing drive belts on a driven exhaust fan is to loosen
either the fan assembly or the motor in its mount skid and push them toward
each other. Then place the belt around the pulleys and force the fan assembly
and/or motor away from each other and resecure in place.
2) INSTALL V-BELT in the pulley grooves by loosening the belt take-up or the
adjusting screw on the motor. Do not “roll” or “snap” the belt on the pulleys; this
causes too much strain on the pulleys. Be sure the belt doesn’t “bottom” in the
pulley grooves.
3) ALIGN BOTH PULLEY AND SHAFTS by moving the motor on its motor mount.
Hold a straight edge flush against the blower pulley, then move the motor until
the belt is parallel to the straight edge.
4) A PULLEY ALIGNMENT SHORT-CUT Sight down the top of the belt from slightly
above it. If the belt is straight where it leaves the pulley and does not bend, the
alignment is fairly accurate.
5) CHECK BELT TENSION before proceeding further. Remember that a V-belt
“rides” the inside of the pulley faces. Since the sides of the belt wedge in the
pulleys, the V-belt does not have to be tight. It should be as loose as possible
without slipping in the pulley grooves. Belt-Tension Adjustment Tip: Using the
belt take-up or motor-adjusting screw, tighten the belt until the slack side can be
depressed about 3/4″ for each foot of span between the pulleys.
6) WARNING: Excessive belt tension is the most frequent cause of bearing wear
and noise.
B. Filters
1) Always follow the manufacturer or Supervisor’s recommendation of when to replace
filters on an air handler unit. Tips on ensuring the time ex: writing on the side of the
filter with the date when last installed.
2) The U.S. Environmental Protection Agency (EPA) says that indoor air is often more
polluted (typically two to five times more and occasionally 100 times more) than
outdoor air. Most of the "respirable" dust and particles people breathe into their lungs
is approximately three microns or smaller-a fraction of the size of a grain of sand.
3) Good indoor air quality (IAQ) depends on a number of factors, including effective
filtration, which provides the primary defense for building occupants and HVAC
(Heating, Ventilating and Air Conditioning) equipment against particular pollutants.
Today's higher standards in filtration, coupled with rigorous attention paid to filter
selection, helps to produce cleaner, purer air and reduce IAQ-related problems.
Maintenance Positions Study Guide 43. 4) Filter efficiency
a) Facility managers/engineers should work to identify the types and sizes of
particular pollutants in their buildings to determine the best type of HVAC filter for
their needs.
b) Selecting HVAC filters based on the needs of the facility instead of their initial costs will
lead to a review of filter efficiency as a determining factor. Filtration efficiency defines
how well the filter will remove contaminants.
c) Low-efficiency filters are typically used to keep lint and dust from clogging the
heating and cooling coils of an HVAC system. Medium- and high-efficiency filters
are typically used to remove bacteria, pollen, soot and other small particulates.
d) Initial and sustained efficiency are primary performance indicators for HVAC
filters. Initial efficiency refers to the filter's "out-of-the-box" capability. Sustained
efficiency refers to levels maintained throughout a filter's service life.
e) Some filters have lower initial efficiency and don't achieve high efficiency until a
"dirt cake" has built up on them. This happens typically after 30 days. Other filters
offer high initial and sustained efficiency. This means they achieve an ideal
performance level early and maintain that performance level.
f) The American Society of Heating, Refrigerating, and Air-Conditioning Engineers
(ASHRAE) developed two HVAC industry standards that address the efficiency
issue: ASHRAE 52.1 and ASHRAE 52.2. In addition to the performance factors
measured under ASHRAE 52.1 and 52.2, consider these additional variables
when selecting a filter:
1) Moisture resistance. How high humidity and moisture affect the filter;
2) Temperature limitations. How the filter performs at application temperature;
3) Flammability. How the filter performs in flammability tests. Check to see if UL
Class I- or Class II-rated filters are needed to conform to local building codes.
5) Filter technology
a) There are many types of HVAC filters currently on the market, including bulk
media and pre-cut pads; automatic roll filters; disposable panel filters; polyester
rings, sleeves and links; pleated filters, medium- and high-efficiency bag filters;
rigid cell filters; and mini-pleated filters.
b) In most buildings, the best filter choice is a medium-efficiency pleated filter, which
has a higher removal efficiency than low-efficiency filters. It also more adequately
removes the particles that cause IAQ problems, unlike high-efficiency filters,
which would clog.
c) The pleated air filters used in HVAC systems are made with a wide range of
materials (media), including fiberglass, polyester, cotton, paper and synthetic
non-woven materials. Recent advances in non-woven technologies have allowed
for a step-change improvement in both performance and value of synthetic media
over standard cotton/poly blends used in HVAC filters.
d) Unlike traditional cotton/poly media, synthetic media in more modern filters can
be made of thermally bonded, continuous hydrophobic (moisture-repelling)
polyolefin fibers that resist shedding and don't absorb moisture. This is important
in resisting bacterial growth and keeping shed fibers from getting into HVAC coils
or into the breathing air.
e) Moreover, synthetic media can be manufactured without the use of chemical
binders. This means humidity will not affect the web structure and won't cause
glue to soften and thus fibers to shed.
Maintenance Positions Study Guide 44. f)
Unlike cotton/poly filter media, which are made with a surface-loading structure,
synthetic filter media can be made with a gradient density structure. The result is
a solid mechanical foundation that maintains high efficiency over the useful life of
the filter.
g) Finally, synthetic filter media have the ability to apply an electrostatic charge,
which yields a higher initial efficiency and enhances the filter's capture capability.
This is especially the case in the attraction of smaller diameter particles.
h) Electrostatic filtration is different than mechanical filtration, which depends on the
size of the fiber, size of particles being filtered and physical structure of the
media. With mechanical filtration, efficiency tends to build over time as
particulates are collected.
i) With electrostatic filtration, filter fibers are charged, thus creating a force that
attracts particles. This provides high-initial efficiency, and when coupled with a
strong mechanical structure, high-sustained performance can be achieved.
6) HVAC filter maintenance tips
a) Proper filter maintenance is crucial to keeping HVAC ductwork clean. If dirt
accumulates in the ductwork and relative humidity reaches the dew point (so that
condensation occurs), then bacteria and mold may grow.
b) This is especially the case in HVAC systems that have acoustical duct liners.
They're frequently used in air-handler fan housings and supply ducts to reduce
sound transmission and provide thermal insulation.
c) For these reasons, it's imperative to establish appropriate filter change-out
frequency. However, filters should be changed if they become wet, microbial
growth on the filter media is visible, or when filters collapse or become damaged
to the extent that air bypasses the media.
d) Make the job of changing filters as easy as possible. One tip filter suppliers
recommend for making the job of changing filters easier is to place labels on
housing units with information, including number and type of filters, date changed
and pressure drop.
e) Air handlers that are located in difficult-to-access places will be more likely to
suffer from poor air filter maintenance and overall decreased maintenance. Quick
release and hinged access doors for maintenance, therefore, are more desirable
than bolted access panels when security isn't an issue.
f) When changing the filter, make sure that the replacement filter is the correct size
and compatible with your housing. Review the performance value of the filter to
ensure the pressure drop across the filter won't be too great, especially as the
filter loads.
g) Greater resistance will reduce air flow to the unit, creating a negative impact on
the unit's heating/cooling and energy efficiency. This is another key factor to
h) It's important to follow the recommendations of the filter manufacturer/supplier
and HVAC system provider to determine proper procedures and frequencies for
maintaining and changing filters. Also, document inspections and corrective
actions should be taken into account.
Maintenance Positions Study Guide 45. C. Pumps
1) A centrifugal pump works by the conversion of the rotational kinetic energy, typically
from an electric motor or turbine, to an increased static fluid pressure. This action is
described by Bernoulli's principle. The rotation of the pump impeller imparts kinetic
energy to the fluid as it is drawn in from the impeller eye (centre) and is forced
outward through the impeller vanes to the periphery. As the fluid exits the impeller,
the fluid kinetic energy (velocity) is then converted to (static) pressure due to the
change in area the fluid experiences in the volute section. Typically the volute shape
of the pump casing (increasing in volume), or the diffuser vanes (which serve to slow
the fluid, converting to kinetic energy in to flow work) are responsible for the energy
conversion. The energy conversion results in an increased pressure on the
downstream side of the pump, causing flow.
2) General Symptoms of Cavitation and its effects on Pump Performance and Pump
a) Perceptible indications of the cavitation during pump operation are more or less
loud noises, vibrations and an unsteadily working pump. Fluctuations in flow and
discharge pressure take place with a sudden and drastic reduction in head rise
and pump capacity. Depending upon the size and quantum of the bubbles
formed and the severity of their collapse, the pump faces problems ranging from
a partial loss in capacity and head to total failure in pumping along with
irreparable damages to the internal parts. It requires a lot of experience and
thorough investigation of effects of cavitation on pump parts to clearly identify the
type and root causes of cavitation.
3) A detailed description of the general symptoms is given as under. Reduction in
capacity of the pump:
a) The formation of bubbles causes a volume increase decreasing the space
available for the liquid and thus diminish pumping capacity. For example, when
water changes state from liquid to gas its volume increases by approximately
1,700 times. If the bubbles get big enough at the eye of the impeller, the pump
“chokes” i.e. loses all suction resulting in a total reduction in flow. The unequal
and uneven formation and collapse of bubbles causes fluctuations in the flow and
the pumping of liquid occurs in spurts. This symptom is common to all types of
4) Decrease in the head developed:
a) Bubbles unlike liquid are compressible. The head developed diminishes
drastically because energy has to be expended to increase the velocity of the
liquid used to fill up the cavities, as the bubbles collapse. As mentioned earlier,
The Hydraulic Standards Institute defines cavitation as condition of 3 % drop in
head developed across the pump. Like reduction in capacity, this symptom is
also common to all types of cavitations.
b) Thus, the hydraulic effect of a cavitating pump is that the pump performance
drops off of its expected performance curve, referred to as break away,
producing a lower than expected head and flow.
5) Abnormal sound and vibrations:
a) It is movement of bubbles with very high velocities from low-pressure area to a
high-pressure area and subsequent collapse that creates shockwaves producing
Maintenance Positions Study Guide 46. abnormal sounds and vibrations. It has been estimated that during collapse of
bubbles the pressures of the order of 104 atm develops.
b) The sound of cavitation can be described as similar to small hard particles or
gravel rapidly striking or bouncing off the interior parts of a pump or valve.
Various terms like rattling, knocking, crackling are used to describe the abnormal
sounds. The sound of pumps operating while cavitating can range from a lowpitched steady knocking sound (like on a door) to a high-pitched and random
crackling (similar to a metallic impact). People can easily mistake cavitation for a
bad bearing in a pump motor. To distinguish between the noise due to a bad
bearing or cavitation, operate the pump with no flow. The disappearance of noise
will be an indication of cavitation.
c) Similarly, vibration is due to the uneven loading of the impeller as the mixture of
vapor and liquid passes through it, and to the local shock wave that occurs as
each bubble collapses. Very few vibration reference manuals agree on the
primary vibration characteristic associated with pump cavitation. Formation and
collapsing of bubbles will alternate periodically with the frequency resulting out of
the product of speed and number of blades. Some suggest that the vibrations
associated with cavitation produce a broadband peak at high frequencies above
2,000 Hertz. Some suggest that cavitation follows the vane pass frequency
(number of vanes times the running speed frequency) and yet another indicate
that it affects peak vibration amplitude at one times running speed. All of these
indications are correct in that pump cavitation can produce various vibration
frequencies depending on the cavitation type, pump design, installation and use.
The excessive vibration caused by cavitation often subsequently causes a failure
of the pump’s seal and/or bearings. This is the most likely failure mode of a
cavitating pump.
6) Damage to pump parts:
a) Cavitation erosion or pitting
1) During cavitation, the collapse of the bubbles occurs at sonic speed ejecting
destructive micro jets of extremely high velocity (up to 1000 m/s) liquid strong
enough to cause extreme erosion of the pump parts, particularly impellers.
The bubble is trying to collapse from all sides, but if the bubble is lying
against a piece of metal such as the impeller or volute it cannot collapse from
that side. So the fluid comes in from the opposite side at this high velocity
and bangs against the metal creating the impression that the metal was hit
with a "ball pin hammer". The resulting long-term material damage begins to
become visible by so called pits, which are plastic deformations of very small
dimensions (order of magnitude of micrometers). The damage caused due to
action of bubble collapse is commonly referred as Cavitation erosion or
b) Mechanical deformations
1) Apart from erosion of pump parts, in bigger pumps, longer duration of
cavitation condition can result in unbalancing (due to un-equal distribution in
bubble formation and collapse) of radial and axial thrusts on the impeller. This
unbalancing often leads to following mechanical problems:
2) Bending and deflection of shafts,
3) Bearing damage and rubs from radial vibration,
4) Thrust bearing damage from axial movement,
5) Breaking of impeller check-nuts,
6) Seal faces damage etc.
Maintenance Positions Study Guide 47. 7) These mechanical deformations can completely wreck the pump and require
replacement of parts. The cost of such replacements can be huge.
c) Cavitation corrosion
1) Frequently cavitation is combined with corrosion. The implosion of bubbles
destroys existing protective layers making the metal surface permanently
activated for the chemical attack. Thus, in this way even in case of slight
cavitation it may lead to considerable damage to the materials. The rate of
erosion may be accentuated if the liquid itself has corrosive tendencies such
as water with large amounts of dissolved oxygen to acids.
d) Cavitation – heart attack of the pump
a) Thus fundamentally, cavitation refers to an abnormal condition inside the
pump that arises during pump operation due to formation and subsequent
collapse of vapor filled cavities or bubbles inside the liquid being pumped.
The condition of cavitation can obstruct the pump, impair performance and
flow capacity, and damage the impeller and other sensitive components. In
short, cavitation can be termed as “the heart attack of the pump”.
D. Refrigeration / Compressors:
1) The Refrigeration Cycle
a) A thorough understanding of the role of a refrigeration compressor cannot exist
without a discussion of the refrigeration cycle, which essentially consists of the
transformation of a liquid to a gas and back again.
There are five main steps to a refrigeration circuit: evaporation, compression,
condensing, receiving and expansion.
b) Evaporation: Liquid refrigerant enters the evaporator. It absorbs heat when it
evaporates, which produces cooling. The refrigerant from the evaporator is fed to
a tank as a weak or saturated superheated gas. The pressure in the tank rises
until it equals the pressure in the evaporator. Refrigerant flow stops and the
temperature in both tank and evaporator both rise to ambient.
c) Compression: To maintain the necessary lower pressures and lower
temperatures, a compressor is needed to remove the vapor. Because the
refrigeration circuit is closed, equilibrium is maintained. That means that if the
compressor removes vapor faster than it can be formed, the pressure will fall and
with it the temperature in the evaporator. Alternately, if the load on the evaporator
rises and the refrigerant evaporates quicker, the temperature and pressure in the
evaporator will rise. The energy that a compressor requires is called compression
input and is transferred to the refrigeration vapor.
d) Condensing: After leaving the compressor, the refrigerant moves to the
condenser, which gives off heat that is transferred to either air or water having a
lower temperature. The amount of heat given off is the heat absorbed by the
refrigerant in the evaporator plus the heat created by compression input. The
byproduct of this is that the vapor changes to a liquid, which is then sent to the
e) Receiving: The pressure in the receiver is higher than the pressure in the
evaporator because of compression, and thus must be lowered to match the
evaporative pressure. This is achieved through the use of an expansion valve.
f) Expansion: Before the liquid enters the expansion valve, the temperature will be
just under the boiling point. Suddenly reducing the pressure in the expansion
valve causes the liquid to boil and evaporate. This evaporation takes place in the
evaporator and the circuit is complete.
Maintenance Positions Study Guide 48. g) There are many different temperatures involved in the operation of a refrigeration
plant, but in principle there are only two pressures: evaporating pressure and
condensing pressure.
2) Types
The main types of refrigeration compressors are reciprocating, screw, scroll and
centrifugal. They are used in refrigeration, heat pumps, and air-conditioning
applications, such as food processing, ice rinks and arenas, and pharmaceutical
a) Rotary Screw Compressors
1) Rotary screw compressors have screw spindles that compress the gas as it
enters from the evaporator. The screw compressor features smooth operation
and minimal maintenance requirements; typically these compressors only
require changes in oil, the oil filter and the air/oil separator. Microprocessorbased controllers are also available for standard rotary compressors, which
allow the rotary to remain loaded 100 percent of the time. There are two
types of rotary screw compressors: single and twin.
b) Reciprocating Compressors
1) A reciprocating compressor uses a piston-actuated unloading mechanism
with spring-loaded pins to raise the suction valve plate from its seat, allowing
the unit to be used at any pressure ratio. This action is similar to an internal
combustion engine in a car. This type of compressor is efficient at both fulland part-load operation. Further advantages include simple controls and the
ability to control the speed through the use of belt drives. The reciprocating
compressor is used in low-horsepower applications.
c) Scroll Compressors
1) Scroll compressors work by moving one spiral element inside another
stationary spiral to produce gas pockets that, as they become smaller,
increase the pressure of the gas. During compression, several pockets are
compressed at once. By maintaining an even number of balanced gas
pockets on opposite sides, the compression forces inside the scroll balance
and reduce vibration inside the compressor. This type of compressor uses
the scroll design instead of a fixed cylinder or a piston or single-sided
compression mechanism, eliminating wasted space in the compression
chamber and eliminating the need to compress gas again and again during
the cycle (recompression). This reduces energy use.
d) Centrifugal Compressors
1) Centrifugal compressors compress refrigerant gas through the centrifugal
force created by rotors that spin at high speed. This energy is then sent to a
diffuser, which converts a portion of it into increased pressure. It does this by
expanding the region of the flow volume to slow the flow velocity of the
working fluid. Diffusers may use airfoils, also known as vanes, to improve
this. Centrifugal compressors are suited for compressing large volumes of
gas to moderate pressures.
E. Chillers/Condensers
1) Absorption Chiller Maintenance - Heat Transfer Components
Maintenance Positions Study Guide 49. a) The life, performance, and cooling capacity of absorption equipment hinges on
keeping heat transfer surfaces free of scale and sludge. Even a thin coating of
scale can significantly reduce capacity. Therefore, cooling tower water chemistry
is critical, and failure to properly treat this water could void manufacturer
b) Scale deposits are best removed chemically. Sludge is best removed
mechanically, usually by removing the headers and loosening the deposits with a
stiff bristle brush. The loosened material is then flushed from the tubes with clear
2) Absorption Chiller Maintenance Purging Non-condensable Gases
a) All absorption chillers must be purged of non-condensable gases to maintain
performance. The three methods used are steam jet, solution jet (or "motor less
purge"), or a vacuum pump, with the vacuum pump being by far the most
b) Non-condensable gases migrate to the area of lowest pressure in the absorption
chiller (the evaporator) where a small portion of the vapor is extracted and
condensed in the purge unit using cooling water. Non-condensables are then
evacuated by the vacuum pump. In normal operation, the purge system should
operate about one hour a week. The vacuum pump oil level should be observed,
maintained, and changed as necessary. Oil purge pump motor bearings should
be inspected and replaced, and the belt adjusted as needed. In addition, the
vacuum pump should be flooded with oil during seasonal shutdown to prevent
internal corrosion.
a) Purging of non-condensables can be accomplished using a "motorless purge"
b) Where motorless purging is used, an optional vacuum pump can also be
used for evacuation.
c) In all cases, the operator should log purge operation and monitor purge
operation trends. Increasing purge operation signals increasing in-leakage of
air and moisture. (Source:
d) Industrial water chillers are available with a choice of two types of refrigerant
condensers: Water-Cooled or Air-Cooled.
e) It is important to choose the right type of condensing medium for the
environment the water chiller will operate in. Ill suited condensers may
affect process cooling and thus affect production quality.
f) Refrigerant condensers are necessary to remove latent heat from the
high pressure refrigerant gas. This heat is introduced by the
g) The condenser is a heat exchanger where refrigerant gas flows on one side
and the condensing medium (air or water) flows on the other side. The latent
Maintenance Positions Study Guide 50. heat from the refrigerant gas is transferred to the condensing medium. As the
heat is transferred to the condensing medium, the refrigerant gas cools and
“condenses” into a liquid.
h) Low temperature liquid refrigerant is required to chill the process water.
i) A basic example is where the facilities that do not have adequate water
supplies from tower or city water supplies will find that an air-Cooled
condenser is better suited than a water-cooled condenser because an aircooled condenser does not require an external water supply.
3) The two condenser types include:
a) Water-Cooled. These condensers use a tube and shell heat exchanger where
plant water circulates on one side and refrigerant on the other.
b) Air-Cooled. These condensers use a fined tubed heat exchanger and motor
driven fans or centrifugal blowers to move air through the condenser.
1. Adequate water supplies are available from tower, city or well sources.
2. Water supply is of good quality.
3. Heat recovery is not practical or unimportant.
4. Plant ambient temperatures consistently exceed 95°F.
5. Ambient air is polluted with large dust and dirt particles.
1. Offer lower capital investment.
2. Operates more efficiently on hot summer days.
3. Easier to operate.
4. Does not offer summer ventilation.
1. Adequate water supply not available from
tower or well sources.
2. Water supply is not of good quality.
3. Heat recovery is practical and important.
4. Plant ambient temperature will not consistently
exceed 95°F.
5. Ambient air is not polluted with large dust and dirt particles.
1. Somewhat more costly to purchase and operate.
2. Gives less cooling on hot summer days.
3. Consumes more electricity.
4. Offers summer ventilation and winter supplement heating.
F. Cooling Towers
1) What is Enthalpy?
a) Enthalpy is the heat content or total heat contained in a substance at any given
2) What is a (wet, atmospheric) cooling tower?
a) A cooling tower is a heat rejection device, which extracts waste heat to the
atmosphere though the cooling of a water stream to a lower temperature. The
type of heat rejection in a cooling tower is termed "evaporative" in that it allows a
small portion of the water being cooled to evaporate into a moving air stream to
Maintenance Positions Study Guide 51. b)
provide significant cooling to the rest of that water stream. The heat from the
water stream transferred to the air stream raises the air's temperature and its
relative humidity to 100%, and this air is discharged to the atmosphere.
Evaporative heat rejection devices such as cooling towers are commonly used to
provide significantly lower water temperatures than achievable with "air cooled"
or "dry" heat rejection devices, like the radiator in a car, thereby achieving more
cost-effective and energy efficient operation of systems in need of cooling. Think
of the times you've seen something hot be rapidly cooled by putting water on it,
which evaporates, cooling rapidly, such as an overheated car radiator. The
cooling potential of a wet surface is much better than a dry one.
Common applications for cooling towers are providing cooled water for airconditioning, manufacturing and electric power generation. The smallest cooling
towers are designed to handle water streams of only a few gallons of water per
minute supplied in small pipes like those might see in a residence, while the
largest cool hundreds of thousands of gallons per minute supplied in pipes as
much as 15 feet (about 5 meters) in diameter on a large power plant.
The generic term "cooling tower" is used to describe both direct (open circuit)
and indirect (closed circuit) heat rejection equipment. While most think of a
"cooling tower" as an open direct contact heat rejection device, the indirect
cooling tower, sometimes referred to as a "closed circuit cooling tower" is
nonetheless also a cooling tower.
A direct, or open circuit cooling tower is an enclosed structure with internal
means to distribute the warm water fed to it over a labyrinth-like packing or "fill."
The fill provides a vastly expanded air-water interface for heating of the air and
evaporation to take place. The water is cooled as it descends through the fill by
gravity while in direct contact with air that passes over it. The cooled water is
then collected in a cold water basin below the fill from which it is pumped back
through the process to absorb more heat. The heated and moisture laden air
leaving the fill is discharged to the atmosphere at a point remote enough from the
air inlets to prevent its being drawn back into the cooling tower.
The fill may consist of multiple, mainly vertical, wetted surfaces upon which a thin
film of water spreads (film fill), or several levels of horizontal splash elements
which create a cascade of many small droplets that have a large combined
surface area (splash fill).
An indirect, or closed circuit cooling tower involves no direct contact of the air
and the fluid, usually water or a glycol mixture, being cooled. Unlike the open
cooling tower, the indirect cooling tower has two separate fluid circuits. One is an
external circuit in which water is recirculated on the outside of the second circuit,
which is tube bundles (closed coils) which are connected to the process for the
hot fluid being cooled and returned in a closed circuit. Air is drawn through the
recirculating water cascading over the outside of the hot tubes, providing
evaporative cooling similar to an open cooling tower. In operation the heat flows
from the internal fluid circuit, through the tube walls of the coils, to the external
circuit and then by heating of the air and evaporation of some of the water, to the
atmosphere. Operation of the indirect cooling towers is therefore very similar to
the open cooling tower with one exception. The process fluid being cooled is
contained in a "closed" circuit and is not directly exposed to the atmosphere or
the recirculated external water.
In a counter-flow cooling tower air travels upward through the fill or tube bundles,
opposite to the downward motion of the water. In a cross-flow cooling tower, air
moves horizontally through the fill as the water moves downward.
Maintenance Positions Study Guide 52. h) Cooling towers are also characterized by the means by which air is moved.
Mechanical-draft cooling towers rely on power-driven fans to draw or force the air
through the tower. Natural-draft cooling towers use the buoyancy of the exhaust
air rising in a tall chimney to provide the draft. A fan-assisted natural-draft cooling
tower employs mechanical draft to augment the buoyancy effect. Many early
cooling towers relied only on prevailing wind to generate the draft of air.
i) If cooled water is returned from the cooling tower to be reused, some water must
be added to replace, or make-up, the portion of the flow that evaporates.
Because evaporation consists of pure water, the concentration of dissolved
minerals and other solids in circulating water will tend to increase unless some
means of dissolved-solids control, such as blow-down, is provided. Some water
is also lost by droplets being carried out with the exhaust air (drift), but this is
typically reduced to a very small amount by installing baffle-like devices, called
drift eliminators, to collect the droplets. The make-up amount must equal the total
of the evaporation, blow-down, drift, and other water losses such as wind blowout
and leakage, to maintain a steady water level.
3) Some useful terms, commonly used in the cooling tower industry:
a) Drift - Water droplets that are carried out of the cooling tower with the exhaust
air. Drift droplets have the same concentration of impurities as the water entering
the tower. The drift rate is typically reduced by employing baffle-like devices,
called drift eliminators, through which the air must travel after leaving the fill and
spray zones of the tower.
b) Blow-out - Water droplets blown out of the cooling tower by wind, generally at the
air inlet openings. Water may also be lost, in the absence of wind, through
splashing or misting. Devices such as wind screens, louvers, splash deflectors
and water diverters are used to limit these losses.
c) Plume - The stream of saturated exhaust air leaving the cooling tower. The
plume is visible when water vapor it contains condenses in contact with cooler
ambient air, like the saturated air in one's breath fogs on a cold day. Under
certain conditions, a cooling tower plume may present fogging or icing hazards to
its surroundings. Note that the water evaporated in the cooling process is "pure"
water, in contrast to the very small percentage of drift droplets or water blown out
of the air inlets.
d) Blow-down - The portion of the circulating water flow that is removed in order to
maintain the amount of dissolved solids and other impurities at an acceptable
e) Leaching - The loss of wood preservative chemicals by the washing action of the
water flowing through a wood structure cooling tower.
f) Noise - Sound energy emitted by a cooling tower and heard (recorded) at a given
distance and direction. The sound is generated by the impact of falling water, by
the movement of air by fans, the fan blades moving in the structure, and the
motors, gearboxes or drive belts. (Source:
Maintenance Positions Study Guide 53. G. Troubleshooting:
1) A/C System Troubleshooting
The following is an general A/C system troubleshooting guide. Realize that it is generic and
many of the things listed here may not apply to all types of systems.
Symptom / Possible Cause
Low Compressor Discharge Pressure
1. Leak in system 2. Defective expansion
valve 3. Suction valve closed 4. Freon
shortage 5. Plugged receiver drier 6.
Compressor suction valve leaking 7. Bad reed
valves in compressor
1. Repair leak in system 2. Replace valve 3.
Open valve 4. Add Freon 5. Replace drier 6.
Replace valve 7. Replace reed valves
High Compressor Discharge Pressure
1. Air in system 2. Clogged condenser 3.
Discharge valve closed 4. Overcharged
system 5. Insufficient condenser air 6. TXV
stuck in closed position 7. Failed condensing
1. Recharge system 2. Clean condenser 3.
Open valve 4. Remove some refrigerant 5.
Install large fan 6. Replace TXV
7. Replace condensing fan
Low Suction Pressure
1. Refrigerant shortage 2. Worn compressor
piston 3. Compressor head gasket leaking 4.
Kinked or flattened hose 5. Compressor
suction valve leaking 6. Moisture in system 7.
Trash in expansion valve or screen
1. Add refrigerant 2. Replace compressor 3.
Replace head gasket 4. Replace hose 5.
Change valve plate 6. Replace drier 7. Replace
High Suction Pressure
1. Loose expansion valve 2. Overcharged
system 3. Expansion valve stuck open 4.
Compressor reed valves 5. Leaking head
gasket on compressor
1. Tighten valve 2. Remove some refrigerant 3.
Replace expansion valve 4. Replace reed
valves 5. Replace head gasket
Compressor Not Working
1. Broken belt 2. Broken clutch wire or no 12v
power 3. Broken compressor piston 4. Bad
thermostat 5. Bad clutch coil 6. Low
Refrigerant - low pressure switch has cut off
clutch power
1. Replace belt 2. Repair wire or check for
power 3. Replace compressor 4. Replace
thermostat 5. Replace clutch coil 6. Add
Maintenance Positions Study Guide 54. Evaporator Not Cooling
1. Frozen coil, switch set too high 2. Drive belt
slipping 3. Hot air leaks into car 4. Plugged
receiver drier 5. Capillary tube broken 6.
Shortage of refrigerant 7. High head pressure
8. Low suction pressure 9. High suction
pressure 10. Defective expansion valve 11.
Frozen expansion valve
Frozen Evaporator Coil
1. Faulty thermostat 2. Thermostat not set
properly 3. Insufficient evaporator air
1. Turn thermostat switch back 2. Tighten belt
3. Check for holes or open vents4. Replace
drier 5. Replace expansion valve 6. Add
refrigerant 7. See problem #2 8. See problem
#3 9. See problem #4 10. Replace expansion
valve 11. Evacuate and replace drier
1. Replace thermostat 2. Set to driving
condition 3. Check for excessive duct hose
length, kink or bend.
h) Methods of Refrigerant Leak Detection
1) One of the most difficult areas of sealed system servicing can be trying to find a
refrigerant leak. The leak may exist within a series of tubing that may be up to
hundreds of feet long, or in a component that is not readily accessible, or may
even be totally concealed. It could be in an operating or safety control such as a
pressure switch or possibly right under your nose and you wouldn’t even suspect
it. As we all know, refrigerant leak detection can sometimes be a serviceman’s
a) Having the proper test equipment is at least half of the battle. Unfortunately
there are so many methods of leak detection and so many types of test
equipment and unfortunately, not just one fits every situation. Decisions need
to be made as to the method used and the type of equipment needed for
every leak you need to find.
b) The sole purpose of this section is to help make you aware of the
different methods available and to help you decide on which method is
most appropriate to use in different situations.
c) All of these conditions make leak testing one of the most challenging tasks
faced by service technicians today. The newer EPA rules are now requiring
service technicians to find leaks that are excessive of the law, thus not
allowing technicians the choice of just adding refrigerants every so often to
keep the system in operation. Add to this the cost of refrigerants today and it
becomes imperative that refrigerant leaks must now be found.
d) As you know, there are several methods used to find leaks. Some of the most
popular methods are listed below. They are not in any particular order
because each leak is unique to the situation at large.
2) Bubble Test (Soap Solution)
a) A soap solution can be used when you know the approximate area where a
leak may exist because of sealed service repair recently done or an
electronic leak detector has indicated a leak exists in a particular area of the
sealed system.
b) For example, if you repaired a leak, or replaced a component, or know that a
system has a leak somewhere and/or you observe an area of the system that
Maintenance Positions Study Guide 55. is oil coated, you would probably use a soap solution, in that area, to test for
and pinpoint a leak. It is the simplest and least expensive (material wise)
method known today. It may however be more expensive to use, because of
labor costs, if the technician does not have any idea where the leak could be.
c) Soap solutions are available in many different types. Some have a brush
applicator and others have a dabber (an absorbent ball attached to a stiff wire
inside of the cap.) Some brands may even have a spray applicator to quickly
cover large areas of tubing in a short amount of time. This is an advantage
but is also messy and time consuming to clean up.
d) Some soap solutions even have an antifreeze base to prevent them from
freezing in the winter time. Others may have a lower density to make them
even more sensitive to very tiny leaks.
3) Some pointers when using soap solution:
a) If the system does not contain sufficient pressure for leak detection, the
refrigerant can be recovered from the system and the system re-pressurized
with dry nitrogen to increase the pressure, making it more a probable and
less time consuming way of pin-pointing the leak.
c) Do not pressurize the system or component to be checked, more than the
manufactures leak testing standards. This pressure is usually stated on the
name plate as factory test pressures. If it is not stated on the nameplate, a
safe pressure is usually less than 150 psig
d) There may be times in which an oil spot is noticed in an area of the sealed
system. This is usually a suspect that a refrigerant leak is present in that
area. A soap solution can help to pin-point the leak.
e) Holding the dabber against the suspected leak for a period of time may
provide better results for small leaks.
4) Water Immersion Method
a) This method can only be used if the system is small enough to be emerged in
a tank of water or if the suspected leak exists in a component that can be cut
from the system, sealed and pressurized with a high pressure, dry nitrogen
charge. That system or component of the system is then submerged into a
water tank. Then the technician watches for bubbles escaping from the leak.
5) Some pointers when using the submersion method:
a) A detergent can be added to the water to decrease surface tension, which
helps to prevent the leaking gas from clinging to the side of the component.
b) Hot water in the tank sometimes helps to increase the pressure inside the
component or piping system. If dry nitrogen is used, this does not help
because nitrogen does not increase significantly. If refrigerant is contained in
the system or component, it may help considerably to increase the pressure
and increase the chance of finding the leak.
6) Halide Torch
a) A halide torch is an inexpensive leak detector that is fast and reliable, but can
only be used to detect chlorinated refrigerants. It can be used to detect leaks
as small as ½ ounce per year.
Maintenance Positions Study Guide 56. b) A halide torch works on the principle that air is drawn over a copper element
heated by a hydrocarbon fuel. If halogenated refrigerant vapors are present,
the flame changes from a blue color to a bluish green color.
c) It is not as sensitive as electronic leak detectors and is somewhat awkward
and could be dangerous because of the open flame.
7) Dye Interception Method
b) This is method in which a dye is inserted into the system in hopes that some
day, the leak allows the escape of a colored dye where the leak exists. This
dye becomes visible after a period of time, notifying the technician where the
leak is.
c) Ultraviolet leak detection dyes are also available. These dye kits sometime
requires more expensive equipment to detect the leak. This may include an
ultraviolet lamp, ultraviolet dye, and some method of getting the dye into the
system without letting any moisture or air into the system. These dye
methods may be more time consuming because of the time it takes to leak
the dye and be visible to the human eye.
d) Some considerations when using a dye might be:
1) The dye may be considered a contaminate to the sealed system and is
difficult to get into the system without moisture contamination. Even the
slightest bit of moisture is detrimental to the longevity of any sealed
2) This method can be (and usually is) a mess and normally requires some
type of clean up. The dye usually ends up in your test equipment (gauge
manifold and/or refrigerant hoses) and is usually a time consuming mess
to clean up
3) This method is usually time consuming because it could take several
hours or days for the dye to leak from the leak source indicating a leak.
4) This method also means you have to have access to all of the system,
which may limit its use
8) Standing Hold Test
e) This method consists of pressurizing the system with a high pressure, dry
nitrogen gas. A pressure, usually between 100 to 200 psig, for a period of
time and then identify whether or not the pressure drops during this time. The
higher the pressure, the faster you can determine if a leak is present.
Fortunately, dry nitrogen experiences very little pressure changes when it is
exposed to small temperature changes.
a) Do not pressure the system or component, to be checked, more than the
manufactures leak testing standards. This pressure is sometimes stated on
the nameplate as test pressures but if not, using less than 150 psig is usually
b) The disadvantage of this method of leak detection is that it can only be used
if you have a system that can be shut down for a period of time (usually
overnight or longer.) This can be very time consuming because some lowlevel leaks may require a holding period of up to 48 hours or more. It’s not
that you have to stay with the system for that period of time, it’s just the fact
that the system may need to be out of operation for that amount of time.
Maintenance Positions Study Guide 57. c) The advantage however is that this method will positively identify whether or
not a leak exists by monitoring pressure drop. If any pressure drop occurs, it
means a leak is definitely present. The disadvantage: This method does not
identify where the leak exists, only if a leak is or is not present.
10) Isolation of the Sealed System
a) This is a time consuming method of the standing hold test but is sometimes
your only choice. It is usually used when you have no physical access to
components in which you suspect are leaking or when you want to identify
which part of the system contains the leak. Some examples might be: a
concealed refrigerant line, an in-wall condenser, an in-wall evaporator, or any
component in which you do not have access to.
b) This process would include isolation of the component (suspected of leaking)
from the rest of the system. This is done by breaking that part of the system
apart from the rest of system, sealing it, and pressurizing only that
component with dry nitrogen. Then use the standing hold test covered before.
If the system’s pressure drops fast, there is a large leak present in that
component or section of the system. If the system’s pressure drops slowly,
there is a small leak present. If the pressure remains the same, that
component does not leak.
c) This method can limit your leak detection labor time only if the system can be
out of order for a period of time. Once the component leaking is identified,
determine if repairs can be made or not. If not, that particular component can
be replaced if it at all possible.
d) A process tube adapter kit could save you some time. It can be quickly
connected to the part of the system that has been cut out. This eliminates
having to make a mechanical or brazed connection.
11) Electronic Leak Detectors
a) Using an electronic leak detector is generally the fastest way to find an
unknown leak.
b) They can be used to quickly find a leak, or to find the area in which the leak
exists, in a sealed system when you don’t even know where to start. An
electronic leak detector gets you really close to the leak. After you find the
area in which the leak is detected, you can usually decrease the sensitivity of
the some types of detectors to pin point the area of the leak. The leak area is
then coated with soap solution to verify the exact point of the leak.
c) Electronic leak detectors must be designed to detect a certain type of or
multiple types refrigerant, i.e. (CFC, HFC, HFCF, etc.)
12) Warning:
a) You must be careful because you can waste a lot of time if you’re using a
detector that is not compatible with the refrigerant that is contained in the
system you are leak testing.
b) Know your leak detector’s capabilities and also what it is not capable of
c) Carbon monoxide and alcohol can affect the sensitivity of most electronic
leak detectors. Be sure neither is present when leak detecting.
d) Operation usually depends on a variation of current flow caused by ionization
of decomposed refrigerant between two oppositely charged platinum
Maintenance Positions Study Guide 58. e) Most electronic leak detectors are not recommended to be used in
atmospheres that contain flammable or explosive vapors. The sensor
operates at extremely high temperatures. If this sensor comes in contact with
a combustible gas, an explosion will occur. This can be very dangerous
and costly. It will probably ruin your electronic leak detector and/or possibly
damage or destroy a building because of an explosion. Most manufactures
will not honor warrantee products against abuse, and exposing a refrigerant
sensor to combustible gases, constitutes abuse.
13) Some Pointers when using electronic leak detectors:
a) If the leak is suspected to be very small, it may be possible to enclose the
suspected area for a period of time to allow the leaking refrigerant time to
accumulate. When accumulated, it is then more readily sensed by the
b) This may be done by:
a) Wrapping a suspected leak in cellophane and leaving it pressurized with
a refrigerant charge for a period of time. Then using an electronic leak
detector, cut the cellophane at the bottom while using an electronic
detector to detect any refrigerant that may have accumulated in the pouch
over time.
b) It is permissible to add a little vapor R-22 to a system and then repressurize the system to a higher pressure by adding nitrogen to the
system containing the R-22 holding charge. This increases the chance of
finding the leak and is considered, by the EPA, as “De Minimus Release”
(a good faith effort of finding a leak that may prevent future refrigerant
venting through a leak that is not found.)
c) If a refrigerant component or piping section that is suspected of leaking, is
inside a compartment (such as a freezer/refrigerator compartment or a
small room) and a leak is suspected in that part of the system. That
section could be easily isolated by closing a door and trapping the
components in an enclosed space.
d) If the detectors alarm goes off, you have verified the leak exists in that
component, tubing or area.
e) Again, re-pressurizing the system to a higher pressure and of course,
having refrigerant in the system, will accelerate the process.
f) Refrigerant has a higher specific volume than air; therefore refrigerants
will fall when exposed to atmospheric pressures. This means leak
detecting on the bottom sides of the piping or components will be more
effective in detecting a leak and will save you time.
Maintenance Positions Study Guide 59. 6.
A. The Laws of Energy: Thermodynamics
1) Energy
Energy is defined as the ability to do work. There are two basic types of energy,
kinetic energy and potential energy.
2) Kinetic energy
Kinetic energy is energy in motion. For example water spilling over a dam can be
harnessed to do work since it is in motion. Since the water is moving it is said to
have kinetic energy. Heat and light are other examples of kinetic energy.
3) Heat
Heat is a measure of the total amount of kinetic energy that a group of molecules or
atoms has because of the random movement of the molecules.
4) Temperature
Temperature is the average (as opposed to the total) amount of kinetic energy that a
group of molecules or atoms has because of random movement of the molecules.
5) Potential energy
Potential energy is stored energy. For example the water backed up behind the dam
is not doing work, but could do work if released. Chemical energy, the energy stored
in chemical bonds is potential energy as is the electrical energy stored in a battery.
All chemical reactions, indeed just about the entire living world, are governed by two
basic laws of energy or thermodynamics.
6) Thermodynamics
Thermodynamics is the branch of science dealing with the laws and theories related
to energy in the universe. There are two main laws of thermodynamics, the first and
second law. There also is a third law as well which says that absolute zero exists, but
it is really a consequence of the other two so we will not deal with it here.
7) First law of thermodynamics
The First Law of Thermodynamics says that energy under normal conditions cannot
be created or destroyed, simply transformed from one type of energy to another.
Thus a chemical reaction such as lighting a match does not create new energy but
only converts one type of energy to another. What's happening with the match is that
as the match is burnt, potential energy is released and converted to heat and light,
kinetic energy. In the cell there are many types of energy transformations: light to
chemical (photosynthesis), chemical to chemical (cellular respiration), chemical to
electrical (nervous system), and chemical to mechanical (muscles). So the first law is
of fundamental importance.
8) Second law of thermodynamics
The second law is a bit more complex than the first law, but basically it says that any
time you do work, including any time you make an energy transformation, some of
the starting energy is going to be lost as heat. So when you drive a car some of the
gasoline's energy is lost right a way as heat, some gets turned into mechanical
energy to move the car. Even some of this mechanical energy is also lost as heat.
Maintenance Positions Study Guide 60. For instance if you feel your car's tires at the end of a trip they will be hot from friction
with the road. This heat is an energy loss and is a consequence of the second law.
Maintenance Positions Study Guide 61. 7. Plumbing
A. Flush Valve Maintenance:
1) How To Repair Diaphragm on Flush Valve
a) The roaring ferocity of a torn flushometer diaphragm can be nerve-racking.
b) Here's how the beast malfunctions: you trip the handle; the diaphragm rises
inside the valve, roars, and then snaps closed before enough water has passed
through. The only way you can get a full flush is to hold the handle until the job is
done. And that's a pain. So read on.
c) Shut off water supply at stop valve or at main cutoff in basement.
d) Tape jaws of wrench or large cap to prevent damage to fixtures.
e) Place wrench on large cap of cover assembly, and turn in Counterclockwise
direction until assembly is removed (Fig. 83A).
f) Place fingers inside flush valve and find diaphragm. Vulcanized into it is a brass
fitting held in place by several rings. This is called the diaphragm operating
assembly (Fig. 83B).
g) Remove assembly.
h) Examine diaphragm for holes or tears.
i) Unscrew diaphragm bushing from seat guide in counterclockwise direction.
j) Remove diaphragm and replace with new one, making sure that the strainer side
of the bleeder valve is next to seat guide holder.
2) Reassemble into flush valve as follows:
a) Place seat guide downward into valve
b) Place auxiliary valve seat in center.
3) Replace cover assembly, first lubricating threads with petroleum jelly. Tighten slowly.
4) Turn on water and test.
5) After procedure is completed, it may be necessary to adjust the length of the flush as
a) Remove cap nut.
b) Insert screwdriver through top of valve seat assembly and turn in a clockwise and
counterclockwise direction until proper flush is achieved. Clockwise turning
shortens the flush and counterclockwise turning lengthens the flush.
c) Replace cap nut.
d) Test flush.
Maintenance Positions Study Guide 62. (Source:
B. Aerators:
1) Most faucets have an aerator. No matter which faucet you have, nearly all have a
little device in the spout, this is the aerator, that mixes air with the out- pouring water.
This device is designed to reduce the splattering that would otherwise happen when
the faucet is turned on, plus it saves water too.
a) Determine which faucets have reduced water flow. Make sure the shut-off valve
(typically under the sink) is turned on all the way. If this is the case and the water
flow is restricted, then the problem is most likely trash or other debris caught in
the faucet aerator located right above where the water comes out of the faucet
b) Remember how all these parts came off. With the water shut off to the faucet in
question, try to unscrew the aerator housing with your fingers.
c) If the aerator does become loose, carefully keep unscrewing it and take it
completely off. DO NOT loose track of how the parts came off because you will
need to know how to replace all of them correctly for the faucet to work right.
d) Use a rag when using pliers to loosen the aerator so you don't mar up the
faucet. If the aerator does not unscrew using your fingers, no sweat, grab a rag
and a set of pliers. Using the rag to keep from marring up the aerator housing,
apply pliers and loosen it.
e) Notice the screen. That's where the debris will build up. With the aerator
completely unscrewed and with knowledge of which parts came out first, flush all
debris from the little screen which is the main part of an aerator. This is likely the
reason for the water flow reduction.
f) Rinse water over the screen and all other parts in the aerator. Make sure you
don't drop any parts.
Maintenance Positions Study Guide 63. g) After cleaning all parts, reassemble the aerator parts in the correct order back
into the faucet. Gently tighten with fingers.
h) Turn the water back on and hopefully see the smooth flowing water coming from
your once clogged faucet.
C. Soldering
1) Caution: Please read our safety information before attempting any testing,
maintenance or repairs. Wear eye protection and gloves when soldering and
when working with flux. Flux is a toxic substance. Some equipment may rely on a
cold water supply. Take appropriate steps to shut down any equipment that may
be adversely affected by shutting off the water supply. Such equipment includes,
but is not limited to, a boiler or other heating system.
a) Note: Because you are working with a flame, often in a confined space, be
aware of flammable materials near where you are working. In some cases,
you may need to set up a non-flammable heat shield between the solder joint
and flammable material nearby. Check with your local authority for applicable
codes about the work you wish to perform and the necessity of permits before
you begin your project.
b) When copper pipes are fitted together, there is a very small gap between the
two pieces. When the pipes are heated, and solder is touched to the pipes,
the solder melts and is drawn up into the gap through capillary action. Once
the gap is filled, and the heat removed, the solder forms a seal and makes a
watertight joint.
c) Soldering pipes is easy once you get the hang of it. The key is to recognize
that you are heating the pipes, not the solder. The heated copper melts the
solder. Follow the steps in this guide and you should be able to make
watertight joints. It is recommended that you practice a few times on some
spare parts until you feel confident.
2) How To Solder Copper Pipes
a) Remove all burrs from the inside and outside edges of the pipe with a
deburring tool. Small burrs can result in variety of problems in the lifespan of
the water supply system.
b) Clean the outside of the pipe to a brilliant shine with a copper pipe cleaning
brush, or simply use steel wool or emery cloth. If the copper is not clean, the
solder may not bond properly and the joint may leak.
c) Clean the inside of the female fitting in the same way as in step 1.
d) Apply acid-free flux to both the outside of the male fitting and the inside of the
female fitting. Flux further cleans the copper plus helps to prevent oxidation
as the pipe heats up. If the pipe becomes oxidized, the joint may leak.
e) Join the two pieces securely together.
f) Unroll about four inches of solder and straighten it. You will use the roll or
container as a handle when applying the solder.
g) Light the torch and apply the flame to the joint. Move the flame around to
ensure that you heat the metal on the opposite side from you.
h) When the flux begins to bubble and spit, touch the tip of the solder to the
joint. The solder should melt immediately and disappear into the joint.
Remove the heat. Work quickly because the pipe's temperature will drop
quickly. Move the tip of the solder around the entire joint to ensure that solder
Maintenance Positions Study Guide 64. i)
fills in all the way around. If the joint stopped taking up solder because the
solder was not melting, then quickly add more heat so that more solder can
be applied.
Once the joint will take no more solder it will build up outside of the joint and
begin to drip. Use a damp rag to wipe the joint clean.
3) Notes:
a) Always check for leaks after the pipe has cooled.
b) If you overheat the copper, it will oxidize and that prevents the solder from
c) If the joint leaks, you must open the joint, remove all the solder and start over
by cleaning the metal and applying flux. It may be easier to start over with
new fittings.
d) Always use lead-free solder.
e) Make sure the pipes are completely dry or it will interfere with the bonding of
the solder.
f) If you cannot completely stop the flow of water from the pipe you are working
on, it may be impossible to heat the pipe hot enough. Take a wad of white
bread (without the crust) and stuff it into the pipe. This will hold the water
back for a minute or two. After that the bread will dissolve harmlessly in the
pipe and is easily flushed out.
g) If you use MAPP gas instead of propane, it burns much hotter and will heat
the copper very quickly compared to propane. If you are used to propane,
practice with MAPP before beginning work.
D. Backflow
1) What is Backflow?
A backflow prevention device is used to protect water supplies from contamination or
pollution. Many types of backflow prevention devices also have test cocks so that
they can be tested or examined to ensure that they are functioning properly.
a) The Environmental Protection Agency (EPA) holds local water suppliers
responsible for maintaining a certain amount of purity in potable water systems.
Many states and/or local municipalities require annual testing of backflow
prevention assemblies.
b) Backflow prevention protects the potable water system from minor, moderate,
and severe hazards. There are over 10,000 reported cases of backflow
contamination each year. Some cases can be fatal. Backflow devices are
required by law where needed and must be installed in accordance with
plumbing or building codes. A backflow assembly has test cocks and shut-off
valves and must be tested each year, if relocated or repaired, and when
2) Common Irrigation Backflow Prevention Assemblies
Maintenance Positions Study Guide 65. a) A Pressure Vacuum Breaker (PVB) is a type of backflow prevention
device, used to keep non-potable (or contaminated) water from entering
the water supply. A PVB is similar to an atmospheric vacuum breaker
(AVB), except that the PVB contains a spring-loaded poppet. This makes
it acceptable for applications that are high hazard or where valves are
downstream. Pressure vacuum breakers must be protected from freezing
when installed outdoors. PVBs usually have test cocks, to which
specially-calibrated gauges are attached, in order to ensure that they are
functioning properly.
PVBs are manufactured by Watts, Febco, Zurn and other manufacturers.
Backflow prevention devices such as PVBs are regulated by the
International Plumbing Code, but may also be required by government
a) A reduced pressure (RP) backflow prevention device is a device used to
protect the potable water supply from contaminated water. An RP valve
consists of an automatic pressure relief valve in between two check
valves. The pressure relief valve opens to the atmosphere in the event of
a reduction in the pressure differential between the first two chambers of
the device.
The assembly is considered to provide redundant means of protection
because: (1) check valves keep water flowing in one direction only, and;
(2) the relief valve will operate in the event the supply pressure drops
below atmospheric pressure.
Reduced pressure backflow preventers can be abbreviated RP, RPP
(Reduced Pressure Principle) and RPZ (Reduced Pressure Zone). RP
assemblies protect against backsiphonage and backpressure, and may
be used where a potential hazard exists. RP valves can be found in
commercial buildings, hospitals, and industrial applications.
Under no circumstances should a backflow device be bypassed.
Maintenance Positions Study Guide 66. 8. Electrical
A. Conduit installation
1) Several general requirements apply to all types of conduit installation. All runs
must be installed as a complete system before any conductors are pulled into
them. In other words, a run of conduit (to include conduit, fittings, and supports)
must be complete before the conductors are installed. A run of conduit should be
as straight and direct as possible. When a number of conduit runs are to be
installed parallel and next to each other, install them all at the same time. The
minimum size raceway that can be installed is generally 1/2-inch electrical trade
size. There are exceptions to this rule depending on specific locations. The
exceptions for each type are outlined in the NEC.
2) All types of conduit must be reamed after they have been cut. Conduit threaded
in the field must be threaded with a die that has a 3/4-inch taper per foot. Also,
never use threaded couplings with running threads. Running threads weaken the
conduit and may come loose. Threaded couplings and connectors used with any
type of conduit must be made with tight connections. When the couplings or
connectors are to be buried in concrete or masonry they must be the concretetight type. When installed in wet locations, they must be the watertight type.
3) Fittings for EMT are of two general types ¾ watertight fittings that may be used
outdoors or in any location and fittings that provide strong mechanical and
electrical connections, but may be used only in dry locations. The watertight
fittings join sections of tubing by means of a five-piece compression fitting.
(Figure 4-1).
Figure 4-1. Five-piece compression fitting
4) To put a watertight fitting together, use the following steps:
Step 1. Place a gland nut and compression ring over the end of each piece of
tubing (in that order).
Step 2. Slip a double-threaded ring (called the body) over the end of each
Step 3. Screw the gland nuts onto the body and tighten them to squeeze the
compression rings. The rings form a watertight seal.
A similar fitting having only three pieces is used to make a watertight joint to metal
boxes (Figure 4-2).
Maintenance Positions Study Guide 67. Figure 4-2. Three-piece fitting
5) To make a watertight joint to a metal box, use the following steps:
Step 1. Place the large nut and compression ring on the end of the EMT.
Step 2. Place the double-threaded body over the end.
Step 3. Screw the nut onto the body to squeeze the compression ring and
make a watertight seal.
Step 4. Use the exposed threads on the body to secure the EMT to a
weatherproof box using a locknut and bushing (Figure 4-3).
Figure 4-3. Opened three-piece fitting
Fittings for use in dry locations are simpler to use and less expensive. One type
consists of a sleeve and two or four setscrews (Figure 4-4).
Figure 4-4. Dry-locations fittings
Another form of coupling is made by using a plain sleeve and an indenting tool
(Figure 4-5).
Figure 4-5. Plain sleeve and indenting tool coupling
Maintenance Positions Study Guide 68. To put on an indented coupling, use the following steps:
Step 1. Place the sleeve over the ends to be joined.
Step 2. Use the indenting tool to make indents in the coupling and the
tubing to secure the joint. The tool makes two indents at once
on either side of the coupling (Figure 4-6).
Step 3. Use the tool twice, 1/4 turn apart, on each end of the coupling,
to make a total weight of eight indents at the joint.
Figure 4-6. Indenting tool
Fittings used for rigid-steel and PVC conduit are similar to those used for EMT.
Threaded and threadless couplings and connectors are available for use with
rigid-steel and PVC conduit and PVC. The threadless fittings are installed in the
same way as those for EMT. The advantage of using threadless couplings and
connectors is that threading the conduit is not required. Because EMT has a thin
wall, it cannot be threaded, thus threaded couplings cannot be used with EMT
(Figure 4-7).
Figure 4-7. Threadless couplings and connectors
On rigid steel conduit threaded couplings are screwed onto the threaded ends of the
conduit and tightened with a pipe wrench (Figure 4-8).
Figure 4-8. Threaded coupling
Rigid-steel and PVC conduit is connected to electrical boxes by locknuts (Figure 4-9). The
locknuts are tightened against each side of the box wall. The bushing is placed over the end of
the conduit to provide the conductor with protection from physical damage.
Maintenance Positions Study Guide 69. Figure 4-9. Box connector
Fittings for flexible metallic conduit are either internally or externally attached to the conduit. The
internal type is designed to screw into the spiral of the conduit. This type of connector covers
the end of the conduit completely, protecting the conductors from contact with the cut edge of
the conduit. Externally attached connectors are secured to the conduit with clamping screws
(Figure 4-10).
Figure 4-10. Flexible metallic conduit connector
a) When using these connectors, make sure that the cut end of the conduit
is pushed as far as possible into the connector, covering the cut end and
protecting the conductors from damage.
b) The spiral construction of flexible metallic conduit causes it to have a
higher electrical resistance per foot than solid metallic conduit. For this
reason, flexible metallic conduit should not be used as a grounding
conductor. An additional bare or green-insulated grounding conductor
should be included with the current-carrying conductors in flexible conduit
A special type of metallic flexible metallic conduit is made for use in wet areas. It is called liquidtight. Liquid-tight fittings are available for use with this conduit (Figure 4-11).
Maintenance Positions Study Guide 70. Figure 4-11. Flexible metallic, liquid-tight conduit connector
Connections are made in PVC conduit by cementing two pieces of PVC together (Figure 4-12).
Joints must first be coated with primer. The cement used is actually a solvent that softens the
plastic at the joint and allows the softened areas to flow together to form a weld. The resulting
joint is watertight and strong. PVC conduit can be cut readily with any fine-tooth saw.
Figure 4-12. PVC coupling
6) When you run conduit from one point to another, you often need to make
more turns (total of 360°) than the NEC allows in a single run. When this is
the case, you can use a fitting called a conduit body. A conduit body, as
defined in the NEC, is "a separate portion of a conduit or tubing system that
provides access through a removable cover to the interior of the system at a
junction of two or more sections of the system or at a terminal point of the
system." Figure 3-3, page 3-3, shows some of the more common conduit
bodies and covers.
7) A conduit body is put in conduit between two outlets to keep the bends within
NEC limits for a single run (Figure 4-13). As you can see, the run below has
bends that total 360º, which is all the NEC permits. Therefore, a conduit body
had to be installed so that the conduit could be continued to the box on the
Maintenance Positions Study Guide 71. Figure 4-13. Conduit body usage
Conduit must be supported by straps or hangers throughout the entire run (Figure 4-14).
Figure 4-14. Conduit supports
8) On a wooden surface, nails or wood screws can be used to secure the
straps. On brick or concrete surfaces, you must first make a hole with a star
or carbide drill and then install an expansion anchor. Use an expansion tool
to force the anchors apart, forming a wedge to hold the anchor in the hole.
Secure the strap to the surface with machine screws attached to the anchor.
On tile or other hollow material, secure the straps with toggle bolts. If the
installation is made on metal surfaces, you can drill holes to secure the straps
or hangers with machine or sheet-metal screws.
9) The number of supports needed depends on the type of conduit being used.
Holes or notches in framing members may serve as supports. EMT requires
supports within 3 feet of each outlet box, junction box, cabinet, or fitting and
every 10 feet thereafter. Rigid-steel conduit must also be supported within 3
feet of a box. The distance between supports may be increased to 20 feet on
direct vertical runs of rigid-steel conduit from machine tools and other
equipment if threaded couplings are used and the riser is supported at each
end. PVC must be supported as in Table 4-1.
Table 4-1. Supporting distances for PVC
Maximum Space Between
Conduit Size
1/2 to 1 inch
Maintenance Positions Study Guide 3 feet
72. 1 1/4 to 2 inches
5 feet
2 1/2 to 3 inches
6 feet
3 1/2 to 5 inches
7 feet
7 inches
8 feet
10) In addition, PVC must be supported within 3 feet of each opening. Flexible
metallic conduit must be supported at intervals not to exceed 4 1/2 feet and
within 12 inches on each side of every outlet box or fitting. Exceptions to this
are runs of 3 feet or less where flexibility is needed or 6 feet when connecting
light fixtures. After all conduit has been installed, supported, and connected to
the boxes, you are ready to install the conductors. (Source:
B. Introduction to Transformers
1) Shown to the right is a schematic of a Three
Phase Motor Starter. The area highlighted in
yellow is the part of the schematic which
contains the control transformer.
2) The Control Transformer is powered by two of
the three phases. Here it receives power from
phases A and B. This is a single phase
transformer and lowers the voltage to a more
common value which is useful when adding
lights, timers or remote switches not rated for
higher voltages. Transformers have a primary
side and a secondary side. The primary side is
the higher voltage side and the secondary side
is the lower voltage side.
3) Control transformers are rated in volt amps
(VA). The control transformer primary side
voltage must match the incoming line voltage
and the secondary side must match the load
4) The VA rating must be greater than the VA
rating of the load. If lights and timers are used the VA rating must be greater than the
total load. The Secondary Fuse protects the control circuit and transformer from
damage, including fire damage. The VA rating of the transformer is used to properly
select the fuses. The fuse must be smaller than the VA rating of the transformer.
Calculate the fuse size by first determining the size of the transformer.
5) The VA rating is the math formula used in determining the amperage at a given
voltage. A secondary voltage of 120 volts from a 100VA transformer will produce .83
amps... e.g., 100 VA ÷ 120 Volts = .83 Amps. The VA rating is divided by the voltage.
The result is the transformer's output amperage. The Secondary Fuse size for a
Maintenance Positions Study Guide 73. 100VA transformer must be 8/10 Amp or smaller. A fast acting fuse is best. Refer to
the NEC.
6) The primary fusing protects the control transformer from damage, including fire
damage. The VA rating of the transformer is used to properly select the fuses. The
fuses must be matched to the VA rating of the transformer. The VA rating is the math
formula used in determining the amperage at a given voltage. A primary voltage of
480 volts for a 100VA transformer will draw .21 amps...e.g., 100 VA ÷ 480 Volts = .21
7) The VA rating is divided by the voltage. The result is the transformer's input
amperage. The Primary Fuse size for a 100VA transformer must be .21 Amp or
150% larger. Oversizing Primary Fuses is necessary due to the initial load when
power is first applied (the initial load is also referred to as "inrush"). A timed delay
fuse is best. Refer to the NEC.
C. Industrial wiring – 3 Phase
1) Understanding Industrial Wiring
WARNING: You should know and understand safety and follow normal safety
and OSHA guidelines when working with industrial electricity and your work must
conform to local and national building codes and NFPA guidelines.
2) Why 3-Phase?
Normal 110V and 220V is like a big strong fellow who is driving in a tent pin. At
some point, the amount of work that has to be done can be tougher than what
the big fellow can do. With 3-phase, it's like having three guys with sledge
hammers, working together, each hitting the tent pin in a rhythm. While each may
not be doing as much work as the big fellow, together the three of them can drive
in the tent faster because they are hitting it with three small blows for every one
time the big guy is hitting the pin, and the total amount of work being
accomplished is much greater when added up.
3) Advantages of 3-Phase
Often the wiring is smaller, the motor may last longer, and there's a good chance that
a lighter motor will outperform and save more energy than a single-phase motor.
4) Types of 3-Phase Power
a) Common 3 Wire Type
b) Common 4 Wire Type
c) Special 4 Wire Type
d) 3 Wire w/Grounded Hot Leg
e) The type of 3-phase power normally doesn't dictate the operating voltage.
Usually, a voltage meter is required to determine the actual voltages
available, which will also give you some clues about the type of 3-phase. It is
extremely important to perform all the tests, especially if you suspect 3 wire
w/grounded hot leg and will be using only two legs or you may create a dead
short with your connections.
Maintenance Positions Study Guide 74. f)
For traditional reasons, 110V/220V are used, but the actual voltage may be
120V/240V or 125V/250V. It will make more sense, especially when
discussing 3-phase power, as you will see later.
5) Common 3 Wire 3-Phase
a) This is the same as 4 wire 3-phase, and is actually used to describe how the
wiring is done. The same voltages and types of service are still available, and
is normally only done when the lowest voltage is not required, or for highvoltage 3-phase at 440V and above. For clarity, it is mentioned here, but to
understand how it works, see the diagram and details for 4 wire 3-phase.
6) Common 4 Wire 3-Phase
a) The leads marked L1, L2, and L3 are hot leads, or "line," and typically,
diagrams and schematics will continue to use the numbers, but change the
letters to "S" for them after a switch. Sometimes, "M" is used to identify motor
leads. "N" is neutral, and is never switched for this type of 3-phase service.
Which is which? Actually, it is impossible to really know which is L1, L2, and
L3, so we just pick out the three hot leads and start from there.
b) Let's say you check and find that you have 220V 3-phase service. Now, you
can get three separate, single-phase 110V circuits by using L1 & N, L2 & N,
or L3 & N. Also, you have three separate, two-wire 220V circuits by using L1
& L2, L1 & L3, or L2 & L3. For 3-phase, 220V, you need to use all three
leads, L1, L2, and L3. Remember that you can't just decide to use a particular
type of power because you want to — the device must be designed to work
the way you hook it up.
c) At higher voltages, such as 440V 3-phase, the neutral (N) lead may not be
provided, or a separate leads may be supplied for providing a 110V circuit.
d) A special type of 4 wire 3-phase service for 208V is available, too. This is
accomplished in a strange way, and is most often used in lighting circuits
where 208V two-wire and 3-phase service is desired, along with 110V
service. It is less common, but may be found in older buildings and for special
e) 3 Wire w/Grounded Hot Leg is an older type of service. Sometimes, this is
provided with 4 wires, so that 110V service can also be provided. This type of
service is especially hard to test for, since most folks are not familiar with it.
Normally, you have to check for voltage to ground, and the grounded leg will
not show any voltage when a meter is used to check from the ground leg to
ground. However, this lead can only be used for 3-phase, or a short to ground
may occur. Otherwise, this service works like other 3-phase service.
7) Connecting Motors to 3-Phase
a) With single-phase and two-wire 220V, either a shaded pole, CSIR, or CSCR
motor is used so it starts in the correct direction. One of the advantages of 3phase is that the timing of the phases automatically make the motor
directional. Unfortunately, there is no way to know which way the motor will
run ahead of time, so you need to "bump" the motor — turn on the power for
part of a second — to see which way it is going to turn. Some pumps and
most compressors don't care, and when a motor gets older and starts to it is
common to reverse the direction to make the motor last longer. To switch the
direction of rotation on a 3-phase motor, simply switch any two leads.
Maintenance Positions Study Guide 75. 8) Safety Ground
a) Industrial wiring is commonly run inside metal conduits, raceway, or armored
cable, and the safety ground accomplished through these metal enclosures.
The neutral wire is never used to carry the safety ground. Refer to current
NFPA guidelines for proper safety ground installation.
b) Commercial wiring may have different requirements in your local area. Be
certain to check beforehand and do the work in accordance with local building
codes. If in doubt, call your building commissioner.
9) Switches, Controls, and Over-current Protection
a) With the exception of 3 wire 3-phase w/grounded hot leg, all three leads that
are hot need overcurrent protection and should be switched. Some switches
incorporate a starter that has special circuitry to limit the current draw, or
apply a higher voltage, when starting the motor.
b) Some switches and controls will use single-phase, two-wire 220V, or other
combinations, which the actual motor or device that uses a lot of power uses
3-phase. For example, a refrigeration compressor that operates on 220V 3phase may have a 220V 2-wire heater and contactor coil, and a 24V solenoid
valve to control the refrigerant from a cold control. Due to this complexity, it is
extremely important that you know and understand how to read wiring
diagrams and schematics, and be able to determine the voltages and type of
power that each control or device uses.
D. What Is Single-Phasing?
1) `Loads using three-phase power sources are subject to loss of one of the three
phases from the power distribution system. This condition is known as "singlephasing." The loss of a single phase on a three-phase line may be due to a
downed line or a blown pole top fuse on the utility system. Loss of a single phase
may also result from a single-phase overload condition causing one fuse to blow,
or an equipment failure within the end-user's facility.
2) The loss of one phase, or "leg," of a three-phase line causes serious problems
for induction motors. The motor windings overheat due primarily to the flow of
negative-sequence current, a condition that exists anytime there is a phase
voltage imbalance. The loss of a phase also inhibits the motor's ability to operate
at its rated horsepower.
3) If single-phasing occurs when a motor is rotating, the torque produced by the
remaining two positively rotating fields continues to rotate the motor and develop
the torque demanded by the load. The negatively rotating field, the field
associated with the lost phase, produces currents in inductive loads resulting in
voltages in the faulted leg of the three-phase supply. These voltages may be
nearly equal to the phase voltage that was lost. Therefore, detecting a singlephasing condition by measuring the voltages at the motor terminals is usually
4) Three-phase motors may continue to run, but they are not capable of starting on
a single phase. If after the overload devices on the energized phases isolate the
motor, the motor is not then isolated from the lost phase, later attempting a
restart on that single-phase supply will cause the motor to draw locked rotor
Maintenance Positions Study Guide 76. E. Protecting Motors from Single-Phasing
There are a number of ways to protect machines from single-phasing and voltage
unbalance. The diagram below shows a simple protection scheme that has been
used to protect industrial equipment from damage caused by single-phasing.
However, as has already been discussed, regeneration on the missing leg in
inductive loads may make it impossible to detect the loss of phase based on voltage
Three-phase motor single-phasing protection can be provided by time-delay
overcurrent protection fuses sized at 125 percent of the motor running current. To
produce rated torque under single-phasing conditions, motors will draw a line current
of 173 to 200 percent of normal. The overload devices will open to protect the
machine in this case. However, this will occur only where the motors are being
operated at or near their nameplate ratings.
Loss of a single phase to a three-phase motor reduces the power output of that
motor to approximately 57 percent. If the motor is lightly loaded, circulating currents
may damage or destroy the motor windings without the overload devices removing
the motor from the line. This will also occur where motors are oversized for their
application. For example, a 5 horsepower motor is used where the load is only 3
To provide adequate protection from single-phasing conditions, the overload devices
must be sized to the actual full-load RMS current. This may be determined with a
clamp-on meter while the motor is running at its normal full load. For applications
where the load is variable, another means of single-phasing protection will be
An alternate means of single-phasing protection should also be considered where
multiple critical three-phase loads are supplied by a single main service with ground
fault protection. A ground fault in one of the loads may cause the time-delay overload
protection fuse to clear the overcurrent condition on the faulted phase. However, the
overload protection will not clear the ground fault. If the remaining time-delay
overcurrent protection fuses do not open before the ground fault protection relay
operates, power to the remaining critical loads will be lost.
Integrated circuit technology may provide cost-effective solutions for some phase
protection problems. These modules provide a contact closure when voltages of the
proper magnitude and phase are present on the monitored line. The relay contacts
can be wired into the control logic of the protected load to remove primary power or
Maintenance Positions Study Guide 77. to prevent attempted restarts during single-phasing conditions. These units are small
and relatively inexpensive, and may include sensitivity adjustments for various
nominal line voltages.
The diagram below shows a typical application with a single three-phase motor load.
Note that the input to the phase monitor module is taken from the final set of motor
fuses. Connecting the power monitor in this manner allows:
1) installation of the power monitor without disturbing existing protective devices,
2) detection of any failure inside the system that may cause single-phasing.
Outputs may be wired into a control circuit to trip the motor contactor should a failure
An alternative would be to use the module to trip an audible alarm circuit or
automatic dialer as shown in this diagram:
Sensing a single-phase condition is meaningless without a reliable source of tripping
control power. It is common practice to derive the control power from control power
transformers, which are themselves fed from the bus likely to be affected by the
single-phasing condition. The most reliable source of control power is DC supplied
by a station battery. If a reliable alternate source of control power is not available, a
control power transformer configuration must be designed that will assure sufficient
voltage for tripping regardless of which phase has been lost.
Maintenance Positions Study Guide 78. 9. Architectural Drawings
A. How to Read Architect's Drawings
1) The first requirement in constructing a building project is to understand
architectural drawings (blueprints, or in this article, referred to as plans). Here is
a basic overview of reading these plans.
a) Cover sheet. This will contain the project name, the architect's name,
address, and contact information, the project location, and the date. This
page is very similar to the cover of a book.
b) Plan Index. This page (pages) will have an index of plan sheets (and
sometimes their contents). It also will include an abbreviation key, a scale bar
with the plan scale indicated, and occasionally design notes.
c) Location plan. This will have an area map, with an enlarged location map,
usually giving enough information to locate the project site from nearby towns
or highways. This sheet is not found in all sets of plans.
d) Site plans. These pages usually are numbered starting with a "C", such as
Sheet "C 001", "C 002". This will often contain several sheets, showing:
1) Topographical Information. This will indicate to the builder the
topography (slopes or flatness) of the site.
2) Demolition plan. This sheet (or sheets) will show the structures or
features which will be demolished on the site prior to grading for
construction. It will have trees or other items which are to remain noted in
the keynotes.
3) Site utility plans. This sheet (sheets) will indicate the location of existing
underground utilities, so that they can be protected during excavation and
2) Architectural sheets. These sheets will usually be numbered "A", such as "A
001". These sheets will describe and give measurements for the basic footprint
of the building. These plan sheets should include the following.
a) Floor plans. These sheets will show the location of the walls of the building,
and identify components like doors, windows, bathrooms, and other
elements. There will be dimensions noted as distances between, or from
center to center of walls, width of openings for windows and doors, and
changes in floor elevations, if the floor is multilevel.
b) Ceiling plans. Here, the architect will show the types, heights, and other
feature of ceilings in different locations in the building.
c) Roof framing plan. These pages will indicate the layout for joists, rafters,
trusses, bar joists, or other roof framing members, as well as decking and
roofing details.
d) Finish schedule. This is usually a table listing the different finishes in each
individual room. It should list paint colors for each wall, flooring type and
color, ceiling height, type, and color, wall base, and other notes and details
for constructing the finish in areas listed.
e) Door/Window schedule. This table will have a list of doors, describing the
opening, "hand" of doors, window information (often keyed off of the floor
plan, example, window or door type "A", "B", etc.). It will also include
Maintenance Positions Study Guide 79. installation details (cuts) for flashings, attachment methods, and hardware
specifications. There may also be a separate schedule for window and door
finishes. A window example would be "Mill finish, aluminum", a door might be
"Oak, natural finish".
1) Details. This may include bathroom fixture layouts, casework (cabinets),
closet accessories, and other elements not specifically noted on other
2) Elevations. These are views from the exterior, indicating the material
used in exterior walls, (brick, stucco, vinyl, etc), the location of windows
and doors from a side view, the roof slopes, and other elements visible
from the exterior.
3) Structural plans. The structural plans usually are numbered beginning with "S",
as in "S 001" These plans include reinforcement, foundations, slab thicknesses,
framing materials, (lumber, concrete pilasters, structural steel, concrete block,
a) Foundation plan. This sheet will show the size, thickness, and elevation of
footings (footers), with notes regarding the placement of reinforcing bars
(rebar). It will note locations for anchor bolts or weld plate imbeds for
structural steel, and other elements. A footing schedule is often shown on the
first sheet of structural notes, as well as notes regarding the reinforcing
requirements, concrete break strength requirements, and other written
statements for structural strengths, and testing requirements.
b) Framing plan. This will indicate the material used for framing the building.
This may include wood or metal studs, concrete masonry units, or structural
c) Intermediate structural framing plans. These are used for multistory
construction, where each level may require support columns, beams, joists,
decking, and other elements.
4) Plumbing plan. Plumbing drawing pages are numbered beginning with "P".
These sheets will show the location and type of plumbing incorporated in the
a) Plumbing rough-in. This sheet will show the location of pipes which are to be
"stubbed up" to connect the plumbing fixtures to water supply, drain/waste,
and vent systems.
b) Plumbing floor plan. This sheet will show the location and type of plumbing
fixtures, as well as the route pipes will be run (overhead or through walls) for
potable water and drain, waste, and vents.
5) Mechanical drawings. Mechanical pages are numbered beginning with "M"or
“H”. This sheet (or sheets) will show the location of HVAC (heating, ventilation,
and air conditioning) equipment, ductwork, and refrigerant piping, as well as
control wiring.
6) Electrical plan. The electrical drawings are numbered beginning with "E". This
sheet (sheets) shows the location of the electrical circuits, panel boxes, and
fixtures throughout the building, as well as switchgears, subpanels, and
transformers, if incorporated in the building. Special pages found in the electrical
plan pages may be "riser" details, showing the configuration of power supply
Maintenance Positions Study Guide 80. wiring, panel schedules, identifying specific breaker amperages and circuits, and
notes regarding types and gauges of wires and conduit sizes.
7) BMP (Best Management Practices) drawings, or environmental plans. This
sheet will indicate protected areas of the site, erosion control plans, and methods
for preventing environmental damage during construction. There may be details
in the BMP drawings showing tree protection techniques, silt fence installation
requirements, and temporary storm water retainage measures. The requirement
for a BMP plan originates under the environmental protection department of your
local, state, or national governing authority.
1) Locate the element of construction you are reviewing to implement a portion
of your work. If you are laying out the location of the building, you will first
look at the site plan for location of existing buildings, structures, or property
lines so you have a reference point to begin measuring to your building
footprint. Some plans simply give a coordinate grid position using northings
and eastings, and you will need a "total station" surveyor's transit to locate
these points. Here are some example steps for laying out a building foot print
from architectural plans.
8) Lay out your building on the site by either the above referenced plan or the
measurements given on the site plan. Measure to locations, preferably corners,
on one side of the building, and check for any "checkpoints" to verify the
accuracy of your layout. If you cannot absolutely establish an exact building line,
you may have to suppose the location is correct and continue. This is widely
accepted in cases where the site is very large, allowing for tolerance, but on a
crowded lot or site, the location must be exact.
9) Establish the elevation you will work from. This may be a height relative to a
nearby roadway, or an elevation determined from sea level. Your site plan or
architectural floor plan should have a bench mark(a bench mark refers to some
item, such as a manhole lid or survey waypoint with a known elevation) elevation
or a "height above existing grade" as a starting point.
10) Use your plan to measure the location of each corner of the building, including
offsets. Remember what exact element of construction you are using for your
layout. You may mark an outside wall line, a foundation line, or a column line,
depending on the type of construction and the most practical element for making
subsequent measurements. For instance, if you are building a structural steel
building with I-beam columns which require setting anchor bolts to secure them,
you may begin your building layout with the centerline of these columns, where if
you are building a wood-framed residential structure with a monolithic slab floor,
the edge of the slab would be your best choice for the initial layout.
11) Reference the description of various sheets to find an element of construction
you are going to use in the work you will perform. Plumbers use the Architect's
floor plan to locate walls so the pipes they stub up will be concealed inside the
wall cavity when the building is constructed, then use their plumbing floor plan to
find out what types and sizes of pipes are required to service a particular fixture.
12) Use the dimension scale where measurements are not provided. As a rule,
architectural plans are drawn to a "scale". An example would be, 1 inch equals
Maintenance Positions Study Guide 81. 10 feet (1"=10'), so measuring between to walls on the plan sheet means for
each inch, the distance is 10 feet. A scale rule will make this much easier, but be
careful to match the rule scale to the plan's scale. Architects often use a scale of
fractions, such as a 1/32 scale, engineers usually use an inch per foot scale.
Some plans or details are not to scale, and should be marked "(NTS)".
13) Read all notes on a page. Often a particular element has special considerations
which are more easily described verbally than drawn, and notes are a tool the
architect will use to illustrate them. You may see a table of notes on the side of a
sheet, with numbers identifying the note location on the plan (a number with a
circle, square, or triangle around it) and a corresponding numbered statement
describing the situation on the side of the sheet.
14) Learn to recognize the different types of lines the architects and engineers
may use. You should have a specific keynote table for section of plans, and this
will provide information on the abbreviations, symbols, and specific lines used in
each section of the plans. An example would be in the electrical plans, a circuit
may have the "home run" "leg" (the wire going from the first junction box in a
circuit to the panel box (the power source) highlighted or in darker ink than other
circuits, and exposed conduits may be indicated by a solid line, and concealed
conduits by a dotted or broken line. Because there are many different line usages
indicating different type walls, piping, wiring, and other features, you will have to
see individual plan page "key notes" to understand them.
15) Use a "Builder's" calculator to add dimensions when determining distances on
your plans. These are calculators which add feet and inches, fractions, or metric
measurements. Often, an architect will not give a measurement to a specific plan
item, from a baseline such as the "'OBL" (outside building line), so you will need
to be able to add the distances each feature which has a measurement provided,
to get the total distance. An example would be finding the center line of a
bathroom wall to locate the potable water pipe stub up. You may have to add the
distance given from the OBL to the living room wall, then the distance to a
hallway wall, then across a bedroom, to the bathroom wall in question. This might
look like (11' 5) + (5' 2") + (12' 4")= 28' 11".
16) Use CAD (Computer Assisted Design) building plans. If you have a set of
architectural plans in an electronic form, as on a CD, you will need a version of
the original "cad" program which created it to open the files. "AutoCAD" is a
popular, but very expensive, professional design program, and the designer will
usually include a "Viewer" on the disc which you can install on your computer to
view files, so that actual plan pages appear on your screen, but without the full
program, you cannot manipulate design components or change the drawings.
Learn how to handle architect's plans. These sets of documents are often very
large sheets, about 24" X 36", and full construction sets may include dozens, or
hundreds of pages. They are either bound or stapled on the left edge, and
allowing them to be torn from the bindings, ripped apart by mishandling, laid out
in the sun to fade the ink, or left in the rain can make them difficult to use. These
documents can cost hundreds of dollars (US) to replace, so try to protect them,
and have a flat, wide, protected work surface to unroll and read them on.
Maintenance Positions Study Guide 82. 17) Remember that the building plans for a project often include contract documents
other than the Architect's Drawings.
18) Specifications are usually printed and kept in a binder, and they list
descriptions of methods and materials used in the project, as well as testing
methods, quality control information, geotechnical data, and other information
useful in building the project.
19) Look for notes and symbol referring to "alternate bid items" and "addendums".
These may indicate portions of work which are incorporated in the Architect's
drawings, but not in the builder's contract to construct, supply, or install. "NIC" is
an abbreviation for Not In Contract, which means a certain item will be put in a
certain place by the owner after the project is finished. "OFCI" or "GFCI" (Owner
Furnished, Contractor Installed, or Government Furnished, Contractor Installed)
indicate the item is supplied by the customer, but installed by the contractor.
Read and understand all abbreviations used in your plans.
20) Be careful your set of drawings are "original size", since many sets of plans
are provided in "full" and "half" size sets, you will be able to scale distances with
full size drawings without needing to calculate the scale via drafting rulers
a) If the drawings are true half size, you will need to divide your readings from
your ruler by 2. Note: most half size drawings do not state they are half size
or other. Basically to consider anything a half size drawing, it will normally be
less then a 24x18 (Arch C) sized sheet. Keep in mind, sometimes a half size
sheet is called a half size even when its plotted from a 30x44 to a 11x17 size
set, rendering it no longer a true half size.
1) When doing actual construction from architect's plans, keep one set
onsite to record changes with a red ink pen or pencil. These are called
"redline drawings". When a job has been fully constructed, redlines are
usually provided back to the drafter. These drawings are called "Record
Drawings" (RD's) or "As-Builts". These are the site survey redlines which
are different from the original set of drawings (aka corrections).
2) Use a "triangle" type architect's or engineer's rule for scaling distances on
plans. These are shaped so that they offer a flush contact with the plan
page so exact positioning of the rule is possible, decreasing the possibility
of error.
B. Standard Drawing Symbols
1) Graphic symbols are used on construction drawings to reference other drawings
within the set. For example, elevation graphics are used on a floor plan to indicate
which walls are shown as elevations. A detail graphic, which is a circle around an
area of a drawing with an extension to a number, indicates that this area has been
drawn to a larger scale to provide specific details.
2) In order for this system of symbols to work, each drawing within the set has its’ own
unique number. This is usually a combination of numbers. The number for the
individual drawing as well as the page or sheet number on which the specific drawing
appears. Individual drawings may be referenced many times throughout a set of
construction drawings.
3) Graphic symbols are also used to list drawing notes, identify finishes and revisions.
The same graphic is used for one purpose. For example, the same symbol is used
Maintenance Positions Study Guide 83. for every revision. It is the number within the graphic that carries its’ own specific
C. The following are examples of typical drawing symbols:
Drawing Title
Each individual drawing throughout a set has its’ own number,
title and scale.
The top number in the circle indicates the drawing number. In
this case the eight means that this is the eighth drawing on the
The bottom number indicates the sheet number; here it is sheet number A-3.
The title indicates that the drawing is an elevation. The scale of the drawing is shown below.
Drawings on each sheet within the set are numbered in sequence.
The first drawing starts with number one. The second number two. This numbering continues to
include the last drawing on that sheet. Drawing number one typically starts at the top left corner
of the sheet. The numbering for drawings on the next sheet will start in the same manner.
The elevation graphic is typically used on a plan. The drawing on
which they appear, floor plan, furniture plan or partition plan, is
determined by the company producing the drawings. The arrow
around the circle will point to the surface that is shown in elevation. For
example, the arrow will point to the specific wall. Or the arrow will point
to the front of a cabinet, another arrow (symbol) will point the side, and
so on. Each elevation circle will have its own specific number. The top number indicates the
drawing number. The bottom number indicates the sheet number. The graphic shown
references elevation number 8 on sheet number A-3.
The section symbol is used to show where a section is cut through the
A section graphic is used horizontally or vertically, based on the intent of
the information to be provided. The arrow indicates the direction of the
view of the section. The top number indicates the drawing number. The
bottom number indicates the sheet number. In this case the section will be shown on sheet A-5.
It will be the second or number 2 drawing on that sheet.
The detail symbol is used to indicate where a portion of construction is
drawn to a larger scale. A circle or rectangle is placed around this part on
a drawing.
Details are typically placed on plan drawings. In some cases, they are
also used on elevations or sections when it is necessary to enlarge an
area to clearly explain the design and building method.
A detail number is connected to the circle or rectangle. The top number
indicates the drawing number. The bottom number indicates the sheet number. In this case the
detail will be shown on sheet A-7. It will be the number 6 drawing on that page.
Maintenance Positions Study Guide 84. Door Number
Door numbers are used to identify each door separately. Each door has its’
own number.
The door number mark is placed next to the door on a plan drawing. It is also
used on elevations when doors are shown, as a cross-reference.
Within the construction drawing set, a door schedule is included. This lists
each door by number. Detailed information about each door is provided next
to each door number.
A revision graphic is used to indicate that a change was made to
a drawing.
The area of a drawing, where a change was made, is enclosed
with a bubble. The revision number is placed next to the bubbled
The number within the triangle indicates whether it is the first
revision (1) made to the drawing, or the second (2), or the third
(3) and so on.
The revision graphic is also placed within the drawing sheet
border with a date and brief explanation about what the revision entails.
Key Notes
Key note symbols will vary from company to company. Once a symbol is
established for keynotes, it is consistent through out the entire set of
Key notes are commonly used on plan drawings, such as a partition plan or
demolition plan.
Each mark has its own specific number. The notes are numbered in
Each note symbol is placed on the plan with an arrow pointing to the related area.
A specific note number may reference several areas on a drawing.
A legend is provided where each note number is listed along with specific information next to it.
Using key notes simplifies the drawing. The plan is not crowded with notes. Changing the
information on a note in a legend once, is easier than trying to change many notes within a plan.
Finish symbols will vary from company to company. Once a
symbol for finishes is established, it is used consistently throughout
the entire set of drawings.
A finish identification symbol is to show where various finishes are
applied to surfaces. Each finish used in the project has its’ own
unique number, or combination of number and letter. The symbols
are used on plans, elevations, sections and details.
A finishes schedule is included in the set of drawings. Each symbol number is listed in the
schedule with a description of the related material next to it.
Maintenance Positions Study Guide 85. Some of the typical finishes for a project are carpet (C-1), vinyl tile (VT-1), paint (PT-8) or (8),
plastic laminate (PL-3) or (3).
The symbols shown above are typical to construction drawings.
Maintenance Positions Study Guide 86. 
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