Marley cooling tower motor installation, operation and maintenance

Marley cooling tower motor installation, operation and maintenance
cooling tower motor
I N S TA L L AT I O N - O P E R AT I O N - M A I N T E N A N C E
I SSU E D 04/2013
A motor should be inspected on receipt to make sure it was
not damaged during shipment. Turn the shaft by hand to
see that it turns freely. Check motor nameplate for correct
horsepower, voltage, phase and speed.
Check to see that the motor nameplate data agrees with
the voltage and frequency of the power supply provided
for the motor. All induction motors will operate successfully
when the frequency is not more than five percent above or
below the nameplate rating, the voltage is not more than
ten percent above or below the nameplate rating, and the
combined variation in voltage and frequency is not more than
ten percent above or below the nameplate rating.
If a motor is stored before installation, place it in a building
in which air is kept reasonably dry and with a minimum of
temperature fluctuation to prevent moisture condensing in
the motor. Do not store directly on the floor, always block up.
Windings should be meggered at the time the motors are
put in storage.
If motors have space heaters, the heaters should be ener‑
gized when the motors are placed in storage.
NOTE: Remove units from containers when heaters are
energized. Reprotect if necessary.
If outdoor storage is necessary, protection should include
a vapor barrier beneath the motor. The motor should be
blocked up to prevent flooding. All external parts such as
shafts, machined surfaces, and threaded holes should be
protected with a rust inhibitor coating.
Rotate motor shaft monthly to insure that the bearing
surfaces are protected with lubricant.
When a motor is removed from storage, the insulation and
rotor movement should be checked. The insulation should
be checked by applying the potential from a 500 volt meg‑
ohmmeter between the windings and grounded frame for
10 minutes. Resistance readings should be taken at 1 and
10 minutes. Correct the readings to 40°C as discussed on
page 6 of this manual. Calculate the winding polarization
index by dividing the 10 minute reading by the one minute
reading. The recommended minimum value of polarization
index for alternating current machine is:
Class A insulation 1.5
Class B insulation 2.0
Class F insulation 2.0
A low polarization index indicates the insulation should be
cleaned and dried before the motor is placed in operation. It
is possible to operate a motor with a polarization value less
than the minimum listed above but this is not considered
good practice.
The rotor movement is checked by rotating the shaft by
hand. If shaft is not free, contact the motor manufacturer’s
authorized repair shop. Grease in the motor bearings should
be purged at the time of removal from storage. Refer to
LUBRICATION on pages 5 and 6.
The power supply line for the motor should be of sufficient
capacity to carry 125 percent of the motor’s full load current
with a maximum voltage drop of three percent on the line.
The power supply MUST conform with motor nameplate
voltage. Motors rated 200 volts are for a 208 volt sys‑
tem. Motors rated 230/460 volts are for a 240 or 480
volt system. Do not use a 230 or 230/460 volt motor
on a 208 volt system.
Unbalanced voltages in the power supply will greatly in‑
crease the internal losses of the motor, reducing the safe
load the motor can carry. Have the power company correct
any unbalanced voltage.
When motor power is supplied by overhead conductors,
it is advisable to provide a lightning arrestor on each un‑
grounded line.
Wire the motor to the power supply through a disconnect
switch, short‑circuit protection, and suitable magnetic starter
with overload protection. All wiring and fusing should be
in accordance with the National Electrical Code and local
requirements. All motors should be connected as shown on
the nameplate diagram.
The National Electrical Code requires a motor to be in sight
of the controller unless the disconnecting means can be
locked open or unless there is a manually operated switch
in sight of the motor which will disconnect the motor from
its electrical supply.
Overload protection should be installed in all three lines. Size
overload heaters in starters for nameplate service factor and
amps. Overloads for 1.15 service factor motors must kick
out at no more than 125% of nameplate current. Overloads
for 1.0 service factor motors must kick out at no more than
115% of nameplate current.
Overloads should be at the same ambient temperature as
motor. Do not use ambient compensated overloads.
installation – operation
If a two-speed motor is used, be sure control characteristics
are compatible with the motor. A two-speed single-winding
motor requires a different starter than a two-speed twowinding motor. Starters for two-speed motors must include
a minimum time delay of 20 seconds when switching from
high to low speed.
When a disconnect switch is installed between motor and
starter for two speed or part winding start single- speed
motor, a 6‑pole disconnect must be used.
Sleeve bearing motors are usually shipped without oil and
must be oiled before operation. Ball bearing motors are lu‑
bricated for the initial operation by the motor manufacturer;
however, it is recommended that the grease and relief plugs
be removed and the motor bearing housing be examined
for presence of adequate grease before motor is placed in
operation. Add grease if necessary. See instructions on pages
5 and 6 for lubricating ball bearing or sleeve bearing motors.
SAFETY NOTE: Use of two 3‑pole disconnects can
result in one disconnect not being off and unexpected
starts or motor damage.
Turn the rotor by hand to see that it rotates freely. Motor
shaft should be parallel to driven shaft so that there are no
stresses in motor frame.
If reverse operation of mechanical equipment is required,
provide minimum time delay of two minutes before en‑
ergizing motor when changing direction of rotation.
INITIAL STARTING: The motor should bring the fan up to
speed in less than 15 seconds. If it does not, check connec‑
tions, fuses, overloads and voltage at motor terminals during
start‑up period. Run the motor to check the connections
and direction of rotation. If the rotation is incorrect, change
any two of the three motor leads for a three phase motor
or interchange the connections of either the main or start
windings for single phase capacitor start motor.
Check the wiring system for grounds and check the
resistance between all leads for open, bad or incorrect
connections before operating the motor.
The conduit system should be arranged so that trapped
water will collect in a sump equipped with suitable drain
and will not go into the motor terminal box.
When the motor must be moved for coupling removal or belt
adjustment, a short section of flexible, watertight metallic
conduit should be used in place of rigid conduit to protect
the leads to the motor.
Remove all water drain plugs from totally-enclosed motors.
These plugs will be located in the lowest part of the installed
motor. Because of inaccessability of drain plugs with motor
installed on supports, it is sometimes necessary to remove
plugs before the motor is bolted in place.
The drain plugs on explosion-proof motors are automatic
and must not be removed.
NOTE: After motor is installed, it should be run for
three hours at least once a month, even if the tower is
not in operation. This serves to dry out windings and
relubricate bearing surfaces. If motors are purchased
with space heaters, they should be energized as soon
as possible. Use an auxiliary contact on the starter to
turn heater off when motor is running.
CAUTION: Excessive fan cycling may shorten the mo‑
tor's expected service life. On fans 20 feet (6 meter)
diameter and smaller allow for 4 to 5 starts per hour.
On larger fans, 2 or 3 starts per hour may be the limit.
On two speed motors each low speed start and each
high speed start count as one start.
If a two-speed motor is used, allow a time delay of a minimum
of 20 seconds after de‑energizing the high speed winding
and before energizing the low speed winding. Tremendous
strains are placed on driven machinery and motor unless
the motor is allowed to slow to low speed rpm or less before
the low speed winding is energized.
When changing fan direction of rotation, allow a minimum
of two minutes time delay before energizing the fan motor.
DETERMINE LOAD AT MOTOR: With design water rate
and design heat load on the tower, test motor hp as follows:
1.Run motor for 30 minutes. Record motor name plate
2. Measure voltage between all lines at motor terminals.
3. Measure amps in all three lines.
operation – maintenance
4.Average the measured volts and amps and calculate
test horsepower using the following equation:
hp (test) =
Volts x Amps (average)
Volts x Amps (nameplate)
x hp (nameplate)
5. For a given fan pitch setting and RPM, horsepower will
vary directly with the air density which is a function of
temperature and barometric pressure. Because fans are
generally pitched for summer weather horsepower, it is
expected that the motor nameplate horsepower will be
exceeded during winter operation. Assuming 100% heat
load, the temperature rise in the motor will be greater at
the higher horsepower, but the operating temperature
of the motor will actually be lower due to the drop in
ambient temperature. Under these conditions, the higher
horsepower should not be detrimental to the motor.
If the horsepower measurement is taken during cold
weather conditions, the predicted horsepower which will
result during summer operation may be determined by
applying the Factor from Figure 1. For a given location,
the barometric pressure will not normally vary enough
to cause significant error and for this reason, has not
been included in the Factors.
hp (75°F) = hp (40°F) X
Factor (75°F)
Factor (40°F)
= 7.8 x
= 7.43
If it is desired to correct for high or low test barometric
pressure, multiply the predicted horsepower by standard
station barometric pressure and divide by test station
barometric pressure.
*Use ambient dry‑bulb temperatures if checking a forced
draft cooling tower.
Fan motor overloads sized for summer weather will
handle the higher winter horsepower without adjustment
providing they are at the same ambient temperature as
the motor and there is ample heat load on tower.
NORMAL OPERATION: Class B insulated motors are rated
at a maximum total operating temperature of 130°C (266°F).
A thermometer in contact with the winding may indicate a
temperature up to 100°C (212°F). on a protected motor or
up to 115°C (239°F) on a totally enclosed motor without the
motor being too hot. Therefore, a motor that appears to be
hot is not necessarily overloaded. Check with thermometers.
CAUTION: Normal operating temperatures of electric
motors can be hot enough to cause burns. Avoid any
unprotected contact with the surface of an operating
SAFETY NOTE: When working on the fan or fan drive,
make sure the electric motor cannot be started. See
"Installation" section.
To obtain maximum motor life, establish a schedule of main‑
tenance based on the particular application of the motor and
observe the following procedures and precautions:
CLEANING: Remove any oil, dust or scale deposits from the
motor. They can cause excessive insulation temperatures.
Ball Bearing Motors: The following table may be used as
a guide in determining greasing periods for motors:
Figure 1
90 100
Example: The horsepower on an induced draft cooling tower* is
7.8 hp on a 40°F ambient wet‑bulb day. What is the predicted
hp on a 75°F ambient wet‑bulb day?
1 – 30 hp
40 – 250 hp
I n te rm itte n t
12 m on ths
12 m on th s
8 to 16 h ou rs pe r da y
12 m on th s
6 m on th s
Con tin u ou s
8 m on th s
4 m on th s
installation – operation
All greases will deteriorate in time depending upon bearing
size, speed and temperature. The grease used should be
recommended by the motor manufacturer. See instructions
attached to motor for recommended lubricant. If these
instructions have been lost or misplaced, obtain informa‑
tion on lubricant to use and local supply source from motor
manufacturer’s nearest authorized service facility or from
the motor manufacturer. Give complete motor nameplate
data and state clearly that the motor is used on a water
cooling tower. Chevron SRI‑2 is recognized by many motor
manufacturers as a suitable grease for ball bearing motors
for cooling tower service. In general, a polyurethane or lithium
base grease with rust and oxidation inhibitors is recom‑
mended. Use a grease of NLGI No. 2 consistency. Do not
mix greases which are of different types or specifications.
If a change is desired, the motor bearing housing grease
reservoir should be completely cleaned of old grease before
repacking with new grease.
The relief method of greasing motors tends to purge the
bearing housing reservoir of used grease by forcing out
old grease with new grease. Use a plunger type grease
gun which will not fit the bearing grease fill hole too tightly.
race. If the bearing feels rough or binds in spots, it should
be replaced.
Sleeve Bearing Motors: Check oil in sleeve bearings at
least every three months. When journal size is less than two
inches, stop the motor to check the oil level. Old oil should
be drained and replaced at least every year. Clean out oil
well if there is evidence of dirt and sludge.
Motor shaft must be stopped when motor is oiled. The
oil used should be a good grade of mineral oil of light or
medium viscosity (such as SAE No. 10). Turbine oil rather
than automotive crankcase oil is recommended.
Check bearing wear yearly by measuring the air gap with a
feeler gauge. Measure gap in at least four equally spaced
positions at each end of the motor with two of the places
being the lowest point and the point subject to the load pull.
INSULATION: Check insulation resistance with a meg‑
ohmmeter at the end of each shutdown period. Apply the
megohmmeter potential to the winding for one minute
before taking a reading. Correct the reading to 40°C by
using the equation:
R40°C= Kt x Rt and the curve below
Either an excess or insufficient amount of lubricant in the
bearings can cause overheating. To prevent this occurrence,
use the following greasing procedure:
1. Stop motor.
3.Remove grease and relief plugs and free relief hole of
any hardened grease. Use a thin piece of wire in open‑
4.Add grease with a hand operated pressure gun until
new grease appears at the relief hole. Take special care
when greasing the fan end bearing of TEFC motors. The
long relief might be too small for the bearing to relieve
5. Run the motor for approximately one hour after greasing
to permit rotating parts of the bearing to expel excess
grease. Take out some of the excess grease with a thin
piece of wire.
6.Replace plugs and wipe the outside of the bearing
hous­ing clean.
Every few years the motor end brackets should be removed
and the grease reservoirs cleaned and repacked full with
approved ball bearing grease. Open bearings should be
cleaned and repacked.
Bearings should be checked for "roughness" by turning the
outer race slowly with the fingers while holding the inner
Insulation Resistance Temperature Coefficient Kt
2.Wipe grease plugs, outside of bearing housing, and
relief plug, clean.
To Convert Observed Insulation Resistance Rt to 40°C
Multiply by the Temperature Coefficient Kt , Rc – Rt x Kt
Winding Temperature °C
Approximate Insulation Resistance Variation with Temperature
for Rotating machines.
A record of these corrected readings will show a trend in
the insulation condition. It is considered good practice to
recondition a winding if the resistance, having been high on
previous readings, drops to near the recommended minimum
value as calculated by:
Megaohms = 1000 + Rated Voltage of Machine
Motors in continuous operation will stay at a temperature
sufficiently above ambient temperature to prevent conden‑
sation of moisture on and about the windings, even if the
location is very humid. Idle motors, however, accumulate
moisture readily which causes gradual deterioration of in‑
sulation. Where motors are idle for a long time, single‑phase
heating or space heaters may be required to prevent water
Check insulation resistance at least once a year with the
motor at normal operating temperature. Comparison with
several previous readings will give an indication of improve‑
ment or deterioration of insulating value. Readings, to have
comparison value, should be taken under the same condi‑
tions (temperature, operating time since last shutdown, etc.).
Low or falling resistance readings indicate the need for
maintenance. Contact the nearest repair facility authorized
by the motor manufacturer for repair service.
VIBRATION: If vibration occurs, it should be corrected
without delay. Use the following procedure to determine
source of trouble:
1. Check motor mounting to see that fasteners are tight.
2. Disconnect motor from load and run motor separately.
If motor still vibrates, rebalance rotor.
3. If vibration is in mechanical equipment*, check:
a. Alignment of motor with mechanical equipment.
b.Tightness of Geareducer, or belt driven components,
mounting bolts.
Do not start motor without determining that there will
be no interference with free rotation of the fan drive.
Motor manufacturers’ warranties run for 12 months in service
but not to exceed 18 months from date of manufacture. Mo‑
tor manufacturers warrant their products to be of the type
and quality described, suitable for the service for which they
are supplied, and free of defects in materials and workman‑
ship. Failures from causes external to the motor (e.g., single
phasing, operation under prolonged or extensive overload,
damage from handling, improper maintenance, use on other
than the service for which supplied, defect in wiring to power
supply, or deficiency or defect in controls) are not covered
by the motor manufacturers’ warranties.
If a motor failure occurs within the warranty period
because of defect in material or workmanship, the
motor manufacturer is liable and has the right to
remedy the failure by adjustment, repair, or supplying
a replacement motor F.O.B. his factory or authorized
repair facility. In such event, the motor must be delivered
to the nearest repair facility authorized by the motor
manufacturer with notification that the motor is from
a Marley product and that warranty consideration is
requested. Prompt notification of such failure should
be directed to a Marley sales representative.
Motor manufacturers will not accept warranty obligation
for repair of motors by other than their authorized repair
facility nor warranty obligation for materials or workman‑
ship employed in making repairs. Repair shops, including
authorized repair facilities, generally warrant their material
and workmanship for a period of 12 months.
Motor manufacturers’ warranties do not cover cost of
dismounting, transportation to and from repair facilities, or
remounting motors.
c. Unbalance in drive shaft or fan.
*Refer to service manuals for operating and maintenance
1.If overloads are adjustable, set at a higher value
(+15%) for cold weather operation. Readjust for sum‑
mer operation.
If a motor is used only seasonally, it should be cleaned and
lubricated at the close of each season. Refer to motor manu‑
facturer’s recommendations for lubrication and maintenance
instructions. At start of new season, make sure bearings are
adequately lubricated before returning motor to operation.
When tower is not in operation, the motor should be run
for three hours at least once a month. This serves to dry
out windings and relubricate bearing surfaces.
Higher density of cold air at fan increases motor horsepower.
If motor overloads will not allow fan motor operation at high
speed in forward direction, one of the following might be done:
2. Operate motor (fan) in reverse (reverse 2 loads).
3. Operate two‑speed motor at low speed.
cooling tower motor
user manual
S PX C O O L I N G T E C H N O LO G I E S , I N C .
7401 W 129 STREET
P: 913 664 7400
F: 913 664 7439
[email protected]
In the interest of technological progress, all products are subject to design
and/or material change without notice
ISSUED 04/2013 M92-1475A
COPYRIGHT ©2013 SPX Corporation
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