PWA PACKAGED WATER CHILLER 7% THRU 60 TONS INSTALLATION AND
BULLETIN NO. IM 105
PACKAGED WATER CHILLER
7% THRU 60 TONS
13600 INDUSTRIAL PARK BLVD., P.O. BOX 1551, MINNEAPOLIS, MINNESOTA 55440
PHONE: 377-9750 AREA CODE: 612
SPACE REQUIREMENTS FOR
CONNECTIONS AND SERVICING
Unit is designed for indoor application and must be located in an area where the surrounding ambient temperatures are 40 F or above. A good rule of thumb is to place units where ambients are at least 5 degrees above the leaving water temperat
Because of the electric control devices, the units should not be exposed to the weather. A plastic cover over the control box is supplied as temporary protection during transfer.
A reasonably level and sufficiently strong floor is all that is required for the Seasonpak Water
Chiller. If necessary, additional structural members should be provided to transfer the weight of the unit to the nearest beams. Figures 1 and 2 indicate the base plan for the chiller. Refer to
310VING AND PLACING THE UNIT, Page 9 , for foundation information.
When the equipment is received, all items should be carefully checked to make sure that all crates and cartons have been received. All units should be carefully inspected for damage when received. All damage should be reported immediately to the carrier and a claim filed for damage.
Every model PWA Seasonpak with water cooled condensers (Arrangement 1) is supplied with a full refrigerant charge. A holding charge is supplied in condenserless models (Arrangements 2 & 3). For shipment, the charge is contained in the condenser and is isolated by the manual condenser liquid valve and the compressor discharge service valve.
Should the unit be damaged allowing the refrigerant to escape, there may be danger of suffocation in the equipment area since the refrigerant will displace the air. Care should be taken to avoid rough handling or shock due to dropping the unit. N E V E R
LIFT, PUSH OR PULL UNlT FROM ANYTHING
OTHER THAN THE BASE. Refer to MOVING AND
PLACING UNIT, Pages 7 thru 9, and Figures 3 and 4 for further information.
Dimensions of the unit are given in Figures 1 and
The chilled water piping for all units enters and leaves the cooler from the rear. A clearance of
2-3 feet should be provided for this piping and for replacing the filter-driers or servicing the solenoid valves.
The condenser water piping enters and leaves the shell from the ends. Work space must be provided in case water regulating valves are being used and for general servicing.
It is desirable to leave a small walk area on the end opposite that used for replacement of a cooler tube. Figures 1 and 2 indicate the requirements for tube replacement. Clearance for removing a length of tube is required on one end only. The cooler tube is longer than the condenser, therefore, the condenser tube replacement area need not be considered.
Simple three lead connection is all that is required to connect power to the Seasonpak. Wiring should conform with all local and national codes. The system nameplate should be checked to be sure that it agrees with the power supply available. Check Electrical section, Pages 12 to 18, for further information.
WATER TEMPERATURE LIMITS
A. The maximum allowable water temperature to the cooler must not exceed 140’ F under any circumstance, such as change over from heating to cooling.
B. These units must not be operated when the entering water temperature is in excess of 90” F.
MOVING AND PLACING UNIT
MOVING THE UNIT
The light weight of the Seasonpak makes moving a simple matter. The McQuay Seasonpak is skidded to protect the unit from being accidentally damaged from any angle. Table 3 gives the approximate skid dimens ions.
When moving the unit, dollies or simple pipe rollers can be used under the skid or under the base.
Always apply pressure to the base and not to the piping or shells. A long bar helps move the unit easily. Avoid dropping the unit at the end of the roll.
The 4 " channel base is arranged on the skid so that the fork of a standard fork lift truck can be slid easily under (See Figure 3). The forks of the fork lift truck must be across both the front and rear channels before lifting. Always use a fork lift truck on the side opposite the control panel to avoid damaging the controls. Never put the weight of the unit against the condensers.
If the unit must be hoisted, it is desirable to lift from the skid or from the base as indicated in
Figure 4, Page 8. A spreader bar must be used to protect the control cabinet and other areas of the chiller.
E Do not attach slings to piping or equipment. Move unit in the upright horizontal position at all times.
Let unit down gently when lowering from or off rollers.
TABLE 3 OVERALL SHIPPING
M O D E L L E N G T H W I D T H
PWA008 9 8 3 9
98 3 9
PWAOlS 98 39
FIGURE 3 MOVING UNIT WITH FORK LIFT
MOVING AND PLACING UNIT
NOTE: ALWAYS USE SPREADER
BARS TO PROTECT UNIT
PLACING THE UNIT
The small amount of vibration normally encountered with the Seasonpak makes this unit particularly desirable for basement or ground floor installations where the unit can be bolted directly to the floor. The floor construction should be such that the unit will not affect the building structure, or transmit noise and vibration into the structure. See VIBRATION ISOLA-
TORS section for additional mounting information.
Hold down bolt locations are indicated in Figures 1 and 2, Page 5.
VIBRATION ISOLATORS AND
pad be used as the minimum isolation on all upper level installations or areas in which vibration transmission is a consideration.
B. Transfer the unit as indicated under MOVING THE
UNIT, or use the methods as indicated in Figures
3 and 4. In all cases, set the unit in place and level with a spirit level. When spring type isolators are required, install springs running under the main side channels as shown in Figure 5. Foundation hold down bolt locations for vibration isolators are given in Figure 6. A rubber-anti-skid pad should be standard under isolators if hold down bolts are not used.
Rubber-in-shear or spring isolators can be fur- C Vibration eliminators in all water piping connected nished and field placed under each corner of the to the Seasonpak are recommended to avoid strainpackage. It is recommended that a rubber-in-shear ing the piping and transmitting vibration and noise.
A . Piping practices v a r y considerably. In most cases codes. local ordinances and established practices govern the selection and installation of piping.
Local building and safety codes and ordinances should be studied and complied with.
Shut off valves should bc provided at the unit so that normal servicing can be accomplished without draining the system.
It is recommended that temperature and pressure indicators be installed at the inlet and outlet of the shclls’to aid in the normal checking and servicing of the unit. Also. the installation of wire mesh strainers at the pump suction will protect the pump and shells from foreign matter.
A preliminary leak check of the water piping should be made before filling the system.
Vibration eliminators are recommended in all lines connected to the Seasonpak.
CHILLED WATER PIPING
Each cooler is provided with the connections as indicated in Figures 1 and 2, Page 5. Also, a 114”
NPT vent and S/4” NPT drain are provided.
Design the piping so that it has a minimum number of changes in elevation. Include manual or automatic vent valves at the high points of the chilled water piping, so that air can be vented from the water circuit. System pressures can be maintained by using an expansion tank or a combination pressure relief and reducing valve.
All chilled water piping should be insulated to prevent the nuisance of water dripping from the lines.
If insulation is not of the self-contained vapor barrier type, it should be covered with a moisture seal. Do not insulate piping until it has been tested for leaks and until all vent and drain connections have been extended beyond the prop o s e d i n s u l a t i o n t h i c k n e s s t o m a k e t h e m accessible.
The chilled water thermostat is mounted inside the control console, and the control bulb, capillary tubing. and control bulb immersion well are attached to the unit with spring clips. The control bulb well must be field inserted in the first tee installed in the return water line as shown in
Figure 7. The bulb well is supplied with a 112”
NPT male thread. Carefully unsnap the well from the holding clips, remove the retaining bushing and slowly remove the bulb from the well. Install into piping as indicated in Figure 7. When installing the bulb, carefully remove it from the well so as to not wipe off the heat conducting compound supplied in the well. After installing the well, carefully insert the bulb and seal in with the excess compound. Insert the retaining gasket and sealing bushing and clip or tape the cap tube to the water line. Care should be taken not to break or kink the charged capillary tubing. Sufficient cap tube length is provided for bulb insertion up to 10 feet from the unit; however, it is recommended that the bulb well be placed as close to the cooler inlet as possible.
Insulate over thermostat well.
CAUTION: The thermostat bulb should not be ex-
posed to water temperatwes above 140 F since this will damage the control.
FIGURE 7 THERMOSTAT WELL
Only three main power leads need be hooked up to the standard packaged water chiller. From the
power connection block to the motor, the unit is factory wired ready for operation. Table 5, Page
18, gives the recommended lead wire size when only three conductors are used in a raceway. Refer to the National Electrical Code for other type wire or special instructions.
Although there is no specific requirement, inter-locking of a flow switch and the condenser pump
starter (or air cooled condenser fan) is suggested for the most dependable and economical system operation. The cooler pump should operate continuously, even when the unit is not operating. The condenser pump should be field interlocked by connecting the pump starter coil to terminal 7 and terminal 12 as shown on Schematic Wiring Diagrams
1 and 2, and terminals 8 & 14 and 12 & 14 on Schematic Wiring Diagrams 3 and 4, Pages 14 thru 17.
This cycles the condenser pump (or air cooled condenser fan) with the compressor.
Referring to Diagrams 1 thru 4, the flow switch is interlocked by removing jumpers between terminals 13 and 14 for single units and 25 and 26 for dual units, and wiring the switch contacts into the system as is shown on the schematic wiring diagrams. When so wired, the chilled water pump must be operating before power can be applied to start this system. Note that the crankcase heaters will be energized regardless of water flow. The flow switch is recommended and does not have the shortcomings of interlocking the cooler pump starter. A
flow switch must be used for leaving water temperature of
(Refer to Diagrams 1 thru 4).
A. Variations or options in the control system will change the basic wiring diagrams slightly, however, the sequence of events will be similar.
B. The following starting sequence is for dual compressor units. The sequence for single compressor units is identical except for the obvious reference to the second unit. Once the system ON-OFF switch is pushed on the ON position, the unit will operate completely automatically.
1. Check or throw to “auto” position switches
S3 and S4 (pumpdown switches). Switch is in
“auto” position during normal operation.
2. With main power on, power to the control circuit from Ll and L2 is fed through fuse Fl to terminal 25. The power from 25 is fed thru
NC contacts to relay R 3 and R4 to energize the compressor crankcase heaters, when the
compressors are not operating. The indicator lights should show the heaters on. Power is also supplied to the main system On-Off switch,
Closing switch Sl energizes System No. 1 and
System No. 2.
Referring to System No. 1, power at terminal
2 indicates power to the system by lighting the red “Power on” light.
Provided operating safety controls are closed
(FSl, OPl, HP1 and MPl or OLl when external overloads are used), power at terminal 3 will energize safety light, indicating the system is ready to run.
Referring to the standard non-recycle, pumpdown operation of the schematic wiring diagram, relay R1 and R3 are normally open, and power cannot reach compressor starter. Power can reach starter only by energizing Rl which is controlled by thermostat TCl through the compressor lead-lag switch (dual units only) and the pumpdown switch S3.
When cooling is required. power is supplied to
Terminal 4, through water thermostat TC1 energizing relay Rl, indicator light LT5.
When Rl relay is energized, contact Rl will close and open the liquid line solenoid valve
If low pressure control LPl is open, the opening of LLSl will allow refrigerant to flow into the low side building up pressure which will close LPl and the compressor will start.
Meanwhile, time delay TD 3 is timing the second compressor. After the time delay closes, power is fed to control system No. 2 and the same sequence of starting for the second compressor is repeated.
Referring to the schematic wiring diagrams, when thermostat TCl is satisfied, the electrical circuit to terminal No. 4 (or No. 10 for second system), will be broken opening relay Rl de-energizing the liquid line solenoid, and indicator light LT5. The compressor will continue to operate through t.he contacts of R3 relay.
Note that R3 relay is now energized through its own contacts and the compressor is on the pumpdown cycle. When the compressor has pumped most of the liquid refrigerant from the cooler, the low pressure cut out, LPl will open and de-energize R3 relay.
This locks the compressor off the line until the thermostat TCl calls for cooling again, energizing LLSl and Rl and closing LPl.
START UP PROCEDURE
Do not start the Seasonpak until the following steps have been completed.
A. Check all auxiliary components of the installation.
B. Open the compressor suction and discharge shut off valves until back seated. Back seating the valve closes the gauge ports and, if gauges are provided, close valve one turn from full open, toward the closed position.
Always replace seal caps.
Open the manual liquid line shut off valve at the condenser.
If water regulating valves are provided, connect their capillary to the manual valves provided on the condensers and open the manual valves.
Check to see that the water temperature thermostat is installed in the entering water line, that the thermostat well is full of heat conducting compound and that the bulb is secured with the retaining fitting.
Check the compressor oil level. Prior to start-up, the oil level should be in the oil sight-glass.
Fill the water system. The cooler circuits should be filled with clean non-corrosive water.
Check the main system “on-off’ switch to see that it is in the “off’ position. The pump down switches should be thrown to the “auto” position.
Check resets of all safety controls.
Throw the main power disconnect to “On”.
L. Start the auxiliary equipment for the installation.
M. Set the circuit breakers to “On”.
N. Start the system by pushing the system “On-Off’ rocker switch to “On”.
During full load operation, check the compressor oil level. It should be at the center of the oil sight glass during operation.
A. Check the refrigerant charge frequently at the moisture/liquid indicator. A steady clear glass of liquid refrigerant indicates sufficient charge.
A green colored button in the center of the moisture indicator indicates a dry system (should moisture enter the refrigerant, the color will turn yellow). The button was green before it left the factory and should be green after period of operation on start up.
B. Check the temperature control thermostat by observing operation at reduced loads. The thermostat is factory set for 44F leaving chilled water temperature when the entering temperature is 54F.
Refer to CHECKING CONTROLS section, Pages 20 and 21.
Check voltage and amperage of the compressor motor.
Adjust water regulating valve for discharge pressures between 200 and 230 psig for the most economical operating pressure.
Close gauge ports on valves when gauge readings are not required. This will prolong the gauge life.
All controls are checked and adjusted prior to leaving the factory. However, after the unit has operated satisfactorily for a reasonable length of time, a check of the operation and safety controls can be made as indicated below:
OIL PRESSURE SAFETY SWITCH - The oil failure pressure switch is activated by a low pressure differential between the oil pressure and the crankcase pressure. Upon start up, the normally closed pressure actuated contact of this control opens when the pressure differential increases to about
I5 psig. If oil pressure does not reach this differential, the thermal time delay remains energized and opens a bi-metallic safety contact, de-energizing the complete control circuit. If pressure reaches the prescribed differential within 120 seconds, the thermal time delay is de-energized and the control circuit remains closed. If during the operation, the oil pressure differential falls below 10 psig, the thermal time delay is again energized and the control will shut down the compressor.
To check the control, jumper the Freezestat terminals L & M and trip the circuit breaker to the off position. Throw control circuit to “On” to pull in contactor. The contactor should drop out and the safety indicator light should go out after approximately 120 seconds or less. After checking the control, wait approximately 2 to 3 minutes and then reset control manually. The compressor can then be started. Repeated successive operations of the control will require a longer period before it can be reset, since the bi-metal will get hotter and will take more time to cool.
The high pressure switch will shut down the compressor and close the liquid line solenoid valve when the compressor discharge pressure reaches 270 psig for water cooled units, or 360 psig for air cooled units. To check the control, slowly throttle the condenser inlet water or shut down the condenser fan. Observe the cut out point. During testing stand by the System “On-Off’ switch to shut down the unit should the safety device malfunction. Be sure the gauges used are accurate.
The water cooled condensers are supplied with a 300 psig relief valve and the discharge pressure during the test must be kept below 270 psig. For
Aircooled Condenser operation the relief valve will be set for 400 psig.
The control can be manually reset at approximately 70 psig below the cut out point.
LOW PRESSURE CONTROL -
This pressure switch is connected to the low side of the system and its purpose is to shut down the compressor at the end of the pumpdown cycle. It will open at 35 psig and automatically reset at approximately 60 psig. The control can be checked by throwing the individual pumpdown switches to the manual position and observing the cut-out point on the gauge.
FREEZESTAT - The Freezestat is a pressure type control connected to the low side of the system and is set to shut down the system when the pressure drops low enough to be dangerous as far as cooler freeze up is concerned. The control is factory set at 52 to 53 psig. When dropping to this point, the normally open pressure actuated contacts of this control will close, energizing a 220 volt heater. This causes the normally closed bimetallic relay switch of this control to open after a delay of approximately 90 seconds, or less, stopping the compressor and closing the liquid line so 1 en o id valve. The time delay prevents nuisance trip out on momentary low suction pressure and permits the operation of the system on a
The control must, be checked while the system is operating. To check the control, install a volt meter or 220 volt light across terminal Tl and T2 of the low pressure freeze control. There should be a voltage indication or the test light will glow indicating the contacts are opened. Throw the pump down switch to the manual position and check the pressure at which the test light goes out or the volt meter goes to zero. In actual operation, the compressor will shut down and the safety light will go out. The control can be manually reset in about 2 minutes.
E. THERMOSTAT - The thermostats supplied on all packaged chillers are factory calibrated for use in the return water line to the cooler inlet. The thermostat bulb is installed in a well in the return water line in order to be more stable under temperature changes due to load conditions. Figure
7. Page 10 illustrates the recommended method of installing the bulb and well in the return water line. The return water does not change temperature as rapidly as the outlet because of the “fly wheel effect” of the total water system. This results in a stable, non-recycling control of the outlet water temperature.
Normally the thermostat requires no adjustment in the field other than the dial setting for the required control point. The control is preset at the factory to maintain a 44 F average leaving water temperature throughout the loading and unloading sequence of the unit based on a full load cooling range of 10 F. It should be realized however, that there will be a fluctuation in the leaving water
temperature as the unit cycles, unloads and loads.
The magnitude of fluctuation will decrease as the number of capacity control steps increases.
On a two stage thermostat, the dial setting ind i c a t e s t h e a v e r a g e l e a v i n g w a t er temperature that the control will maintain. At a 44 F setting the high stage should actuate at approximately
51 F return water and 41 F leaving based on 10” cooling range. The low stage will open at 46 F return or 41 F leaving (5” TD or 50% capacity).
As the water warms up, the low stage should cut in at approximately 49 F which is the inlet and outlet temperature with the unit off and the high stage should operate at 54 F return or 49 F leaving.
These settings may be checked by operating the unit and slowly regulating the load from full to minimum and return. It may then be necessary to adjust the dial and/or differential between switches to obtain these values.
On a four stage thermostat, the dial setting indicates the cut out point of the low stage switch which represents the average leaving water temperature desired. The high stage or #4 switch should be actuated at approximately 51 F return water temperature, #3 at 49 F, #2 at 4 7 F and #1 at 45 F which is the dial setting. The cut in point will be approximately 2 F higher than the cut out on each switch.
These settings may be checked by operating the unit and slowly reducing the load. The four stage thermostat has a fixed switch differential and fixed differential between switches. DO NOT make any adjustments other than the dial as this is a preset precision control. This dial adjustment must b e made using a screw driver in the slotted gear below the dial. Do not attempt the adjustment by turning the large numbered dial.
FIGURE 10 THERMOSTATS
T W O S T A G E F O U R S T A G E
COMBINATION FILTER DRIER
Each refrigerant circuit is furnished with a full flow replaceable core type filter-drier. In the filterdrier installed in all Seasonpaks, the filters are attached to the flange end cap b y tie rods. The core assembly has a solid plate at the inlet end and a plate with a gasket and fine mesh screen at the outlet. During assembly, a spring at the inlet end is compressed which holds the core in place and exerts a force on the gasket at the outlet end to prevent bypassing. CAUTION - Pump out refrigerant before removing end flange.
B. A condenser manual liquid line shut-off valve is provided for isolating the charge in the condenser, but also serves as the point from which the liquid line can be pumped out. With the line free of liquid, the filterdrier core can be easily replaced.
LIQUID LINE SOLENOID
Each refrigerant circuit is furnished with a liquid line solenoid for automatic pumpdown operation.
All valves have epoxy-clad water proof coil assemblies for standard 220 volt AC - 60 cycle serice. The valve is completely serviceable without removing valve body from the. line. The coils are easily removed without “pumping-out” the liquid line. All valves have a manual operation stem at the side which allows you to open the valve and operate the system in case of a coil malfunction.
Manual stem should be turned 1/2 turn counterclockwise to open bypass port.
CAUTION: Unit cannot be pumped down with valve
in manually opened position. Operator or serviceman should standby to shut unit off.
LIQUID SIGHT GLASS AND
A. The color of the moisture indicator button is an indication of the dryness of the system and is extremely important when the system has been serviced. Immediately after the system has been opened for service, the element button may indicate a chartreuse or yellow color. It is recommended that the equipment operate for about 12 hours to allow this system to reach equilibrium before deciding if the system requires a change of drier cores.
B. The following table is a guide to the moisture content of the system.
C. Bubbles in the sight glass at constant full load conditions indicate a shortage of refrigerant, a plugged filter or a restriction in the liquid line.
However it is not unusual to see bubbles in the sight glass during changing conditions.
WATER FLOW SAFETY SWITCH
water flow safety switch is available as optional equipment for all Model PWA chillers. The flow switch must be field installed and wired into the
Scasonpak control center as indicated on the drawings .
1. The flow switch should be installed in a horizontal run of piping as follows: a. Adjust the flow switch paddle to the size of’ pipe in which it is to be used. (See Figure 11).
b. Apply pipe sealing compound to only the threads of the switch and screw unit into a D” x D” x 1” reducing tee (See Figure 12).
The flow arrow must be pointed in the correct direction.
c. Piping should provide for a straight length before and after the flow switch of at least
5 times the pipe diameter.
a. M a k e sure the arrow on the side of the switch is pointed in the proper direction of flow.
b. The flow switch is designed to handle the control voltage and should only be connected according to the wiring diagram (See Wiring
Diagram inside control box door).
THERMAL EXPANSION VALVE
Each thermal expansion valve is adjusted for 8 to
10 degrees superheat at the factory before shipment. The valve performs only one very simple function; it keeps the evaporator supplied with the proper amount of refrigerant to satisfy the load conditions. Normal suction superheat will be maintained by the expansion valve and it need not be adjusted in the field.
The sensing bulb, of the thermal expansion valve is installed in the closest straight run of suction line from the cooler. The bulb is held on by two clamps around the suction line to assure firm contact with the line. The line is then insulated to remove the effect of surrounding ambients. In case the bulb need be removed, simply slice the insulation on each side of the bulb, remove the clips and then remove the capillary tubing that runs along the suction line from the valve.
In the event the valve itself not necessary to remove the line. All power assemblies and replaced.
needs service, it is valve body from the are easily removed
FOR AT LEAST
TEE Dv x D” x 1”
VIEW FROM END OF COOLER
FS4-3 FLOW SWITCH
The reciprocating semi-hermetic compressor(s) are complete with suction and discharge service valves, integral force feed lubrication system, oil sight glass, oil charging connection, crankcase heater and initial oil charge.
The motor is of the hermetic induction type, 1750 rpm, gas cooled, with inherent thermal protection and supplementary overload protection, where required. The standard unit is wired for across-theline starting. Part winding starting is available as an option.
The compressor is pre-wired and ready to run.
Suction and discharge service valves are closed during shipment and must be opened. just prior to start up. Gauge connections on suction and discharge valves are closed when the valve stem is back seated in the full open position. To in-
crease the life of any gauges supplied, the suction and discharge valve should be back seated except when readings are required. Always replace valve caps with gaskets in place.
The safety control piping connection to the compressor includes the oil failure switch-high pressure oil connection at the oil pump discharge; the oil failure switch-low pressure connection at the compressor crankcase: the high pressure safety connection at the discharge manifold; and the low pressure and freeze safety connection at the suction chamber on the motor end of the compressor.
Shut off valves are never installed in these control lines.
The compressor is pre-charged with sufficient oil for normal operation. In case oil is required, or if unit requires additional oil after installation with a remote air cooled condenser, the compressor may be pumped out on pumpdown cycle, valves closed and oil charged through the filler plug on the side of the compressor oil sump. The plug must ‘be replaced with a sealer and leak checked during operation.
A compressor crankcase heater, internal or external, is provided to minimize refrigerant accumulation in the oil during the off-cycle of the compressor. Excessive refrigerant in the crankcase dilutes the oil causing excessive foaming, oil loss, and in extreme cases, bearing washout and possible failure. The heaters are energized at all times when the unit is shut down. During prolonged shut downs, when the electrical power may be shut off, close the suction and discharge service valves to prevent migration of the refrigerant to the oil and reopen the valves just prior to start up.
Except for minor repairs, such as replacing a suction or discharge reed valve, the compressor is not generally repaired in the field. Exchange compressors are stocked in warehouses throughout the country and the damaged compressor is turned in for credit.
A. Both the cooler and condenser shells are ASME constructed and stamped and are of the straight through tube type with replaceable tubes.
A. The water cooler is of the direct expansion type with removeable internally finned tubes and heavy terneplate baffles. The copper tubes are individually rolled into heavy duty, steel tube sheets and sealed by a cast steel refrigerant head.
B. The water nozzles which enter and leave the shell are at the rear of the unit. No special attention is required for the cooler except tered water should be supplied.
that clean, fil-
The condensers are of the shell and replaceable tube type with integral, externally finned copper tubes, brazed into heavy-duty tube sheets. The tube sheets are then epoxy coated on the water side to protect the metal surfaces. Water heads are rust-resistant, cast iron. Each condenser has full refrigerant pumpdown capacity and is supplied with a purge valve and relief valve, according to
ASA-B9. 1 code.
Each cooler and condenser is supplied with drain and vent connections.
UNIT LESS CONDENSER
Seasonpaks supplied without condensers or with mounted receivers require field piping to a remote condenser of some type. As mentioned under the
REMOTE CONDENSER section of this manual, refrigerant piping should be sized and installed according to the Latest ASHRAE Guide. The design
-of refrigerant piping when using air cooled condensers involves a number of considerations not commonly associated with other types of condensing equipment.
The following discussion is intended for use as a general guide to sound economical and trouble-free piping of air cooled condensers.
is too low, considerable oil may collect in the riser and the horizontal header, causing the compressor to lose its oil and resultant damage due to lack of lubrication.
Another danger is, when the compressor load is increased, the oil that had collected during reduced loads may be carried as a slug through the system and back to the evaporator, where a sudden increase of oil concentration may cause slopover and damage to the compressor.
A. On remote condenser applications having distances of more than 20 feet between compressor or condenser, a discharge line muffler is recommended.
The muffler should be installed as close to the compressor discharge as possible. If an oil separator is used, it will usually perform the same function as a muffler and will eliminate the need for one. A muffler will reduce discharge line pulsations; particularly those which occur during unloaded compressor operation.
D Any horizontal run of discharge piping should be pitched away from the compressor approximately li4” per ft. or more. This is necessary to move by gravity any oil lying in the header. Oil pockets must be avoided as oil needed in the compressor would collect at such points and the compressor crankcase may become starved.
E It is recommended that any discharge lines coming into a horizontal discharge header, rise above the center line of the discharge header. This is necessary to prevent any oil or condensed liquid ‘from draining to the top heads when the compressor is not running.
B. Discharge lines must be designed to handle oil properly and to protect the compressor from damage that may result from condensing liquid refrigerant in the line during shut down. Total friction loss for discharge lines of 3 psi is considered good design. Careful consideration must be given to sizing vertical risers to insure that gas velocities are sufficient at all operating conditions to carry oil. If the velocity in a vertical discharge riser
In designing liquid line, it is important that the liquid reach the expansion valve with a minimum of flash gas since this gas will reduce the capacity of the valve. Because “flashing” can be caused by a pressure drop in the liquid line, the pressure
UNIT LESS CONDENSER
losses due to friction and changes in static head should be kept to a minimum.
A good policy to follow is to size the liquid line from the condenser to the receiver for sewer flow operation. This allows any gas formed in the receiver to vent
the condenser without being bottled up in the receiver. Traps in this liquid drain line should be avoided.
TYPlCAL A R R A N G E M E N T S - Figure No. 13,
Page 26 illustrates a typical piping arrangement involving a remote Aircon located at a higher elevation than the compressor and receiver. This arrangement is commonly encountered when the
Aircon is on a roof and the compressor and receiver are on grade level or in a basement equipment room.
In this case. the design of the discharge line is very critical. If properly sized for full load condition. the gas velocity might he too low at reduced loads to carry oil up through the discharge line and condenser coil. Reducing the discharge line size would increase the gas velocity sufficiently at reduced load conditions; however, when operating at full load, the line might be greatly undersized and thereby create an excessive refrigerant pressure drop. This condition can be overcome in one of the two following ways:
1. The discharge line may be properly sized for the desired pressure drop at full load condition and an oil separator installed at the bottom of the trap on the discharge line from the compressor.
2. A double riser discharge line may be used as shown in Figure 14, Page 26. Line “A” should be sized to carry the oil at minimum load condition and line “B” should be sized so that at the full load condition both lines would carry oil.
The above two points are particularly important in applications where the refrigerant receiver is directly beneath the air cooled condensers. If two unlike air cooled condensers or unequal piping is used, the resultant unequal refrigerant pressure drop may cause liquid to build up in one of the condenser coils, thereby reducing its effective capacity.
Notice in all illustrations, the hot gas line is looped at the bottom and top of the vertical run.
This is done to prevent oil and condensed rcfrigerant from flowing back into the compressor and causing damage. The highest point in the discharge line should always be above the highest point in the cxondcnsrr coil; and it is advisable to include a purging vent at this point to rclcasc noncondcIis ihI< from the system,
Figure No. 15. Page> 26 illustrates another very common a p p l i c a t i o n where the Aircon is located o n cssc,ntialIy t h e s a m e lcvc~l as the comprcssoI a n d rc~~civer. The dischargcl lint p i p i n g i n t h i s casrx is not t,oo critical. The p r i n c i p a l p r o b l e m encountercxd with this arrangement is that thcrc is frcqucntly insuff’icic>nt vertical distance to allow frccl drai nag<> of 1 iqu id rcfr igclrant from the co~idenser cx)i
I to the
To guard against gas binding in the receiver and l i q u i d buildup in the condenser coil, which arc common to this arrangement. b e certain that the receiver is located as far below the condenser outlet as possible. The liquid line should be free of any traps
if there arc any horizontal run:, they should be pitched down toward the receiver.
Figure No. 16, Page 26 illustrates a third very common application where two or more separate
Aircons arc piped together on a single compressor.
First of all, it is very important that the two
Aircons have the same capacity so that the rcfrigerant pressure drop through each unit is equal.
Secondly, the piping should be arranged so that the lengths of run to and from each Aircon are equal.
FIGURE 18 TROUBLE SYSTEM CHART
PROBLEM lompressor w i l l n o t r u n .
POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS a) Main switch open.
C i r c u i t b r e a k e r s o p e n .
b) F u s e B l o w n .
a ) C l o s e s w i t c h .
b) C h e c k e l e c t r i c a l c i r c u i t s a n d m o t o r w i n d i n g f o r s h o r t s o r g r o u n d s . i n v e s t i g a t e f o r p o s s i b l e o v e r l o a d i n g . R e p l a c e f u s e o r r e s e t breakers a f t e r f a u l t i s c o r r e c t e d .
c) T h e r m a l o v e r l o a d s t r i p p e d o r f u s e s c) Overloads are auto. reset. Check unit closeb l o w n . ly when unit comes back on line.
d) D e f e c t i v e c o n t a c t o r o r c o i l . d) Repdir o r r e p l a c e .
e) System shut down by safety de- e) Determine type and cause of shut-down and v i c e s . c o r r e c t i t b e f o r e r e s e t t i n g s a f e t y s w i t c h .
f) N o c o o l i n g r e q u i r e d . f ) N o n e . W a i t u n t i l u n i t c a l l s f o r c o o l i n g .
g) L i q u i d l i n e s o l e n o i d w i l l n o t o p e n . g) R e p a i r o r r e p l a c e c o i l .
h) M o t o r e l e c t r i c a l t r o u b l e . h) Check motor for opens, short circuit, or burni) L o o s e w i r i n g .
o u t .
1) C h e c k a l l w i r e j u n c t i o n s . T i g h t e n all t e r m i n a l s c r e w s .
C o m p r e s s o r n o i s y o r v i b r a t i n g .
H i g h D i s c h a r g e P r e s s u r e
(I) F l o o d i n g o f r e f r i g e r a n t i n t o c r a n k c a s e .
a) C h e c k s e t t i n g o f e x p a n s i o n v a l v e .
* b ) I m p r o p e r p i p i n g s u p p o r t o n dis- b) Relocate, add, or remove hangers.
charge o r l i q u i d l i n e .
c) w o r n c o m p r e s s o r . c) R e p l a c e .
a ) C o n d e n s e r w a t e r i n s u f f i c i e n t o r o) Reodiust w a t e r r e g u l a t i n g v a l v e . I n v e s t i g a t e temperature too high. w a y s t o i n c r e a s e w a t e r s u p p l y .
b) F o u l e d c o n d e n s e r t u b e s (woterb) C l e a n .
cooled condenser). Clogged spray n o z z l e s ( e v a p o r a t i v e c o n d e n s e r ) .
D i r t y t u b e a n d f i n s u r f a c e ( a i r c o o l e d c o n d e n s e r ) .
c ) N o n - c o n d e n s i b l e s i n s y s t e m . c ) P u r g e t h e n o n - c o n d e n s i b l e s ,
“d) S y s t e m o v e r c h a r g e d w i t h r e f r i g e r a n t . d ) R e m o v e e x c e s s .
e) D i s c h a r g e s h u t o f f v a l v e p a r t i a l l y e) o p e n v a l v e .
c l o s e d .
* f ) C o n d e n s e r u n d e r s i z e d . f) Check c o n d e n s e r r a t i n g t a b l e s a g a i n s t t h e o p e r a t i o n .
g) High ambient conditions. g) Check condenser rating tables against the o p e r a t i o n .
a) Check condenser control operation.
L o w D i s c h a r g e P r e s s u r e a ) F a u l t y c o n d e n s e r t e m p e r a t u r e r e g u l a t i o n .
b ) S u c t i o n s h u t - o f f v a l v e p a r t i a l l y c l o s e d .
c ) I n s u f f i c i e n t r e f r i g e r a n t i n s y s t e m .
d) L o w s u c t i o n p r e s s u r e .
b) O p e n v a l v e .
e ) C o m p r e s s o r o p e r a t i n g u n l o a d e d .
*f) C o n d e n s e r t o o l a r g e .
* g ) L o w a m b i e n t c o n d i t i o n s .
H i g h S u c t i o n P r e s s u r e a ) E x c e s s i v e l o a d .
b ) E x p a n s i o n valve o v e r f e e d i n g .
c ) C h e c k f o r l e a k s . R e p a i r a n d a d d c h a r g e .
d ) S e e C o r r e c t i v e S t e p s f o r l o w s u c t i o n p r e s s u r e b e l o w .
e) See Corrective Steps for failure of cornpressor to load up below.
f) Check condenser rating table against the o p e r a t i o n .
g) Check condenser rating tables against the o p e r a t i o n .
a ) R e d u c e l o a d o r a d d a d d i t i o n a l e q u i p m e n t .
b) Check remote bulb. Regulate superheat.
c) C o m p r e s s o r u n l o a d e r s o p e n .
c) See Corrective Steps below for failure of c o m p r e s s o r t o l o a d u p .
L o w S u c t i o n P r e s s u r e a ) L a c k of r e f r i g e r a n t .
b ) E v a p o r a t o r d i r t y .
c) C l o g g e d l i q u i d l i n e f i l t e r - d r i e r .
d) Clogged suction line or cornpressor s u c t i o n g a s s t r a i n e r s .
a) C h e c k f o r l e a k s . R e p o i r a n d a d d c h a r g e .
b) C l e a n c h e m i c a l l y .
c) R e p l a c e c a r t r i d g e ( s ) .
d) C l e a n s t r a i n e r s .
e ) E x p a n s i o n v a l v e m a l f u n c t i o n i n g . e) Check and reset for proper superheat.
R e p l a c e i f
P o g e 2 8
* R e m o t e c o n d e n s e r m o d e l s .
FIGURE 18 TROUBLE SYSTEM CHART
PROBLEM POSSIBLE CAUSES
POSSIBLE CORRECTIVE STEPS
L o w S u c t i o n P r e s s u r e
( C o n t i n u e d ) f) C o n d e n s i n g t e m p e r a t u r e t o o l o w . f ) C h e c k m e a n s f o r r e g u l a t i n g c o n d e n s i n g t e m p e r a t u r e .
g) C o m p r e s s o r w i l l n o t u n l o a d . g) S e e C o r r e c t i v e S t e p s f o r f a i l u r e o f c o m p r e s s o r t o u n l o a d .
h ) I n s u f f i c i e n t w a t e r f l o w . h) Adiust gpm.
C o m p r e s s o r w i l l n o t u n l o a d o r l o a d u p .
a ) D e f e c t i v e c a p a c i t y c o n t r o l . a ) R e p l a c e .
b) U n l o a d e r m e c h a n i s m d e f e c t i v e . b) R e p l a c e .
c) F a u l t y t h e r m o s t a t s t a g e o r b r o k e n c) R e p l a c e .
copiliory t u b e .
d ) S t a g e s n o t s e t f o r a p p l i c a t i o n . d ) R e s e t t h e r m o s t a t s e t t i n g t o f i t a p p l i c a t i o n .
a ) E r r a t i c w a t e r t h e r m o s t a t . a ) R e p l a c e .
b) I n s u f f i c i e n t w a t e r f l o w . b) Adiust g p m .
C o m p r e s s o r
L o a d i n g - U n l o a d i n g
I n t e r v a l s t o o s h o r t .
L i t t l e o r n o o i l p r e s s u r e .
a) C l o g g e d s u c t i o n o i l s t r a i n e r .
b ) E x c e s s i v e l i q u i d i n c r a n k c a s e .
c) O i l p r e s s u r e g o u g e d e f e c t i v e .
a ) C l e a n .
b) C h e c k c r a n k c a s e h e a t e r . R e s e t e x p a n s i o n v a l v e f o r h i g h e r s u p e r h e a t . C h e c k l i q u i d l i n e s o l e n o i d v a l v e o p e r a t i o n .
c ) Repotr o r r e p l a c e . K e e p v a l v e c l o s e d e x c e p t w h e n t a k i n g r e a d i n g s .
d) R e p l a c e .
d ) L o w - o i l p r e s s u r e s a f e t y s w i t c h d e f e c t i v e .
e ) W o r n o i l p u m p .
f) O i l p u m p r e v e r s i n g g e a r s t u c k i n w r o n g p o s i t i o n .
g) W o r n b e a r i n g s .
h) L o w o i l l e v e l .
i) L o o s e f i t t i n g o n o i l l i n e s .
k) P u m p h o u s i n g g a s k e t l e a k s .
I) F l o o d i n g o f r e f r i g e r a n t i n t o c r a n k c a s e .
C o m p r e s s o r l o s e s oi I. a ) L a c k o f r e f r i g e r a n t e ) R e p l a c e .
f) R e v e r s e d i r e c t i o n o f c o m p r e s s o r r o t a t i o n .
g) R e p l a c e c o m p r e s s o r .
h) A d d o i l .
i) C h e c k a n d t i g h t e n s y s t e m .
k) R e p l a c e g a s k e t .
I) A d j u s t t h e r m a l e x p a n s i o n v a l v e .
*b) V e l o c i t y i n r i s e r s t o o l o w .
*c) O i l t r a p p e d i n l i n e .
a ) C h e c k f o r l e a k s a n d r e p a i r . A d d r e f r i g e r a n t .
b) C h e c k r i s e r s i z e s .
c) C h e c k p i t c h o f l i n e s a n d r e f r i g e r a n t v e l o c i t i e s .
d) R e p l a c e c o m p r e s s o r .
M o t o r o v e r l o a d relays or c i r c u i t b r e a k e r s o p e n .
d) E x c e s s i v e c o m p r e s s i o n r i n g b l o w - b y .
a) L o w v o l t a g e d u r i n g h i g h load c o n d i t i o n s .
b ) D e f e c t i v e o r g r o u n d e d w i r i n g i n m o t o r o r p o w e r c i r c u i t s .
c ) L o o s e p o w e r w i r i n g .
d) H i g h c o n d e n s i n g t e m p e r a t u r e .
a ) C h e c k s u p p l y v o l t a g e f o r e x c e s s i v e l i n e drop.
b) R e p l a c e c o m p r e s s o r - m o t o r .
c) C h e c k a l l c o n n e c t i o n s a n d t i g h t e n .
d ) S e e C o r r e c t i v e S t e p s f o r h i g h d i s c h a r g e p r e s s u r e .
e) C h e c k s u p p l y v o l t a g e . N o t i f y p o w e r company. D o n o t s t a r t u n t i l f a u l t i s c o r r e c t e d .
f) P r o v i d e v e n t i l a t i o n t o r e d u c e h e a t .
C o m p r e s s o r t h e r m a l p r o t e c t o r s w i t c h o p e n
F r e e z e p r o t e c t i o n o p e n s .
e ) P o w e r l i n e f a u l t c a u s i n g unbalanced v o l t a g e .
f) H i g h a m b i e n t t e m p e r a t u r e a r o u n d t h e o v e r l o a d relay.
g) F a i l u r e o f s e c o n d s t a r t e r t o p u l l i n o n p a r t - w i n d i n g s t a r t s y s t e m s .
a ) O p e r a t i n g b e y o n d d e s i g n cond i t i o n s .
b) D i s c h a r g e v a l v e p a r t i a l l y s h u t .
c) B l o w n v a l v e p l a t e g a s k e t .
a ) T h e r m o s t a t s e t t o o l o w .
b) L o w w a t e r f l o w .
c) L o w s u c t i o n p r e s s u r e .
g) R e p a i r or r e p l a c e s t a r t e r o r t i m e d e l a y m e c h a n i s m .
a ) A d d f a c i l i t i e s s o t h a t c o n d i t i o n s a r e w i t h i n a l l o w a b l e l i m i t s .
b) O p e n v a l v e .
c) R e p l a c e g a s k e t .
a ) R e s e t t o 4 0 F o r a b o v e .
b ) A d j u s t gpm.
c) s e e “L ow s u c t i o n p r e s s u r e . ”
m o d e l s .
P a g e 2 9
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project