Centrifugal chillers

SINGLE COMPRESSOR CENTRlFUGAL CHlUERS PEHIPHH 050,063,079,087,100,126 13600 Industrial Park Blvd.. P.O. Bow 1551, Minneapolis, MN 55440

Transcript of Centrifugal chillers

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13600 Industrial Park Blvd.. P.O. Bow 1551, Minneapolis, MN 55440

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It is important that the operator become familiar with theequipment and the system before attempting to operate thechiller.

In addition to reading this manual the operator should studyinstallation and operation bulletin IM 403 and the controldiagram furnished with the unit so that he understands thestarting, operating and shutdown sequences as well as thesafety shutdown modes.

When the McQuay Service technician performs the initialstartup of the chiller he will be available to answer any ques-tions and to instruct in proper operating procedures.

It is recommended that the operator maintain an operatinglog for each individual chiller unit. A suggested log sheet isshown on pages 14 and 15 of this manual.

In addition, a separate maintenance log should be kept ofthe periodic maintenance and servicing activities.

This McQuay centrifugal chiller represents a substantialinvestment and deserves the attention and care normallygiven to keep this equipment in good working order. If theoperator should encounter abnormal or unusual operatingconditions, it is recommended that a McQuay Service techni-cian be consulted.

McQuay conducts training for centrifugal operators at itsfactory Training Center several times a year. These sessionsare structured to provide basic classroom instruction and in-clude hands-on operating and troubleshooting exercises. Forfurther information, contact your McQuay representative.


Each centrifugal chiller is assigned a set of identifyingnumbers which are used to describe the unit features andto identify each individual unit. These four-number groups

All inquiries pertaining to operating and servicing of this

are stamped on each unit nameplate. A typical nameplate

unit should include all identification numbers.Each of the individual components also have nameplates

to provide certain necessary information to the installer and

is shown in Figure 1.

the operator.

The compressor nameplate identifies the compressormodel, style and serial numbers and includes the electricalcharacteristics of the compressor motor. The CEO50 com-

The condenser and evaporator vessels have nameplatesstamped with the maximum working pressure of the vessel.

pressor nameplate also shows the oil pump electrical

It should be noted that the vessel relief valve maximum set-tings coincide with the maximum refrigerant side vessel work-


ing pressure.

NOMENCLATURE CHANGE: The letter “H” has been added behind the first two digits of the model code to signify a hermeticcompressor motor. Models PE and PH are synonymous with PEH and PHH respectively.


The MicroTech Unit Controller is a microprocessor based con-trol panel designed to initiate the step-by-step start functionsof its host centrifugal compressor unit, monitor and regulatethe compressor’s capacity, protect it, and sequence the com-pressor shutdown on temperature demand or in response to


a pre-set time.For full information on the features, installation, operation

and problem analysis of the McQuay Microprocessor controlfor Centrifugal chillers, see Installation and Operation ManualIM 403.

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The compressor capacity is controlled by the movement ofthe inlet vanes, opening or closing to permit the correct quan-tity of refrigerant to enter the wheel or impeller. The vanemovement occurs in response to oil flow from the SA or SBsolenoid valve which, in turn, respond to a control modulesignal. This oil flow activates a piston to rotate the vanes.

VANE OPERATIONThe hydraulic system for the vane control operation consistsof a 4-way normally open solenoid valve. Oil under pressureis directed by the 4-way valve to either or both sides of thepiston depending on whether the control signal is to load,unload or hold.

To open the vanes (or load the compressor) solenoid “SA”is de-energized and solenoid “SB” is energized, allowing oilflow from port SA to one side of the piston to then drainthrough port SB.

To close the vanes (unload compressor) valve SB is de-energized and valve SA is energized to move the piston andvanes to unload position.

When both solenoid valves SA and SB are de-energized,full oil pressure is directed to both sides of the piston throughports SA and SB, thus the vanes are held in that position.Refer to Figure 3 for solenoid action. Note that both solenoidscannot be energized simultaneously.

VANE SPEED ADJUSTMENTThe vane speed at which the capacity control vanes openor close is controlled by the rate of oil bleed-off from the vaneactuating piston. This bleed-off rate is adjustable by position-ing the needle valves on SA and SB solenoid valves locatedin the lube box.

Screwdriver openings in the left side of the lube box per-mit access. The upper opening accesses the SB needle valvefor adjusting the vane OPENING speed for loading the com-pressor (refer to Figure 2). Turn this screw clockwise todecrease the vane opening speed and counterclockwise toincrease the opening speed.

The lower opening accesses the SA needle valve for ad-justing the CLOSING speed for unloading the compressor.The same adjustment applies. clockwise to decrease clos-ing, counterclockwise to increase vane closing.

The vanes are factory set so that from fully closed to fullyopen positioning of the vanes requires about 3 minutes andabout 1 minute from fully open to fully closed. (Exception:CE126 settings are 9 minutes to open and 3 minutes to close).


METERING VALVESThe speed at which the capacity control vanes are openedor closed can be adjusted to suit system operating re-quirements. Adjustable needle valves in the oil drain linesare used to control the rate of bleed-off and consequently the“vane speed”. These needle valves are part of the 4-waysolenoid valve assembly located in the compressor lube box(Figure 2).

The valves are normally factory set so the vanes will movefrom fully closed to fully open in approximately 3 minutes andfrom fully open to fully closed in 1 minute (except CE126).The speed should be slow enough to prevent over-controllingand hunting.


- L E G E N D -- O i l U n d e r P r e s s u r e11,1 Oil Sump Pressure












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- L E G E N D -- O i l U n d e r P r e s s u r eII Oil Sump Pressure









The oil system for the PEH/PHH units provides lubrication voir must remain energized whenever the compressor is off.and heat removal for the compressor bearings and internal IN THE EVENT OF POWER LOSS TO THE HEATERSparts. In addition, the system provides oil under pressure to ALLOWING THE OIL TO COOL, THE HEATERS SHOULDhydraulically operate the piston for positioning the inlet guide BE ENERGIZED FOR 24 HOURS PRIOR TO STARTINGvanes for capacity control. THE COMPRESSOR.

Proper operation of the hydraulic system and bearinglubrication system can be assured only if McQuay recom-mended oil is used. For proper oil selection, consult Table1. Each unit is factory charged with the proper oil. Under nor-mal operation, no additional oil should be needed.

The oil pump for the CEO50 compressor is completely self-contained within the compressor housing. The assembly in-cludes the pump, pump motor, oil heater and oil separator.The oil is pumped through the oil discharge line to the oil filterin the compressor casting and then to the refrigerant-cooledoil cooler.

The MicroTech Microprocessor based control panelmonitors the oil temperature and prevents the unit from star-ting with low oil temperature. This prevents refrigerant ladenoil from being delivered to the bearings upon start-up. Fordetails see page 24 of Installation & Maintenance Bulletin IM403 or the MicroTech control panel.

The other compressor sizes-CE063, 079, 087, 100 and126-utilize a separate oil pump contained in its own oil reser-voir. This assembly includes pump, motor, heater and oilseparator. Oil is pumped through the discharge line, throughthe external oil cooler and then to the oil filter inside the com-pressor housing. Standard PEH/PHH 063-126 units utilizea water-cooled oil cooler although an optional refrigerant-cooled oil cooler is available.

The compresssor is equipped with lubrication protectionfor coast down in the event of a power failure. This is ac-complished by the use of a spring loaded piston in modelsCEO50 thru 100. When the oil pump is started, the piston isforced back by oil pressure, compressing the spring and fill-ing the piston cavity with oil. When the pump stops, the springpressure on the piston forces the oil out to the bearings.

In model CE126 the compressor coast down lubrication issupplied from a gravity feed lube reservoir.


The oil coolers serve to maintain the proper oil temperatureunder normal operating conditions. The coolant flow controlvalve should maintain 9O”F-100°F oil temperature leavingthe oil cooler for optimum operation of the oil system.

Bearings are supplied with oil through internally drilledpassages within the compressor assembly. The oil drainsfrom the bearings into the gear housing and is gravity returnedto the oil sump.



The oil heaters in the gear case and in the oil pump reser-




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The PHH heat recovery chillers are equipped with a hot gasbypass system used to feed discharge gas directly into the

bypass solenoid is energized leaving hot gas bypass available

evaporator when the system load falls below 10% of the com-for use. This introduction of hot gas provides a stable

pressor capacity.refrigerant flow and keeps the machine from short cycling

Light load conditions are signaled by measurement of aunder light load conditions. It also prevents surge during heatrecovery operation.

set percentage of RLA amps by the MicroTech control panel.When the RLA drops to the hot gas setpoint the hot gas

The factory setpoint for bringing on hot gas bypass is 40”of RLA. See IM 403, page 33 for details.



1. Evaporator Pressure Relief Valve2. Chilled Water Connections3. Oil Cooler Water Connections4. Condenser Pressure Relief Valve5. Oil Cooler

6. Oil Pump Assembly7. Discharge Line Check Valve8. Lube (Control Box)9. Motor Cooling Feed Line

10. Compressor Motor Terminal Box

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LUBRICATION (See CAUTION)After the system is once placed into operation, no other ad-ditional oil is required except in the event that repair workbecomes necessary to the oil pump or unless a large amountof oil is lost from the system due to a leak.

If oil must be added with the system under pressure, usea hand pump with its discharge line connected to the ser-vice valve at the bottom of the oil pump. (The CEO50 com-pressor with its internal oil pump is equipped with an oil ser-vice valve on the compressor).

CHANGING OIL FILTERS (See CAUTION)CEO50 Compressors-If the unit is equipped with a suctionline service valve, close this valve and close the valve on themotor cooling liquid line to isolate the compressor. Vent therefrigerant pressure from the compressor. Remove the filtercover and the old filter and install the new filter, open endfirst. Replace the cover using a new gasket. Reopen the suc-tion and liquid line valves.

If the unit is not equipped with a suction line service valve,the unit will have to be pumped down in order to remove thepressure in the compressor before removing the cover andchanging the filter. Refer to later section for pumpdownprocedure.

CEO63 and Larger Compressors-The oil filter in each ofthese machines can be changed by simply isolating the filtercavities. Close the oil discharge line service valve at the oilpump (at the filter on CE126). Remove the filter cover; somefoaming may occur but the check valve should limit leakagefrom other compressor cavaties. Remove the filter, replacewith new element and replace filter cover using new gasket.Reopen valve in pump discharge line.

When the machine is operated again, the oil level shouldbe checked to determine if oil needs to be added to main-tain proper operating level.

CAUTIONImproper servicing of the lubrication system, includingthe addition of excessive or incorrect oil, substitutequality oil filter, or mishandling of the equipment underpressure is hazardous. Only authorized and trained ser-vice personnel should attempt this service. For qualifiedassistance, contact your local McQuay Servicetechnician.

REFRIGERANT CYCLEMaintenance of the refrigerant cycle consists of maintaininga log of the operating conditions, and assuring the unit hasthe proper oil and refrigerant charge. (See the maintenanceschedule and the appropriate operating log at the end of thisbulletin).

At every inspection, the oil, suction and dischargepressures should be noted and recorded, as well as con-denser and chiller water temperatures.

The suction line temperature at the compressor should betaken at least once a month. Subtracting from this, the

saturated temperature equivalent of the suction pressure willgive the superheat. Extreme changes in superheat over aperiod of time will indicate losses of refrigerant or possibledeterioration of the expansion valves. Proper superheat set-ting is 2” to 6°F at full load.

ELECTRICAL SYSTEMMaintenance of the electrical system involves the general re-quirement of keeping contacts clean and connections tightand checking on specific items as follows:







The compressor current draw should be checked and com-pared to nameplate RLA value. Normally the actual cur-rent will be lower since the nameplate rating representsfull load operation. Also check all pump and fan motoramperages and compare with nameplate ratings.

Inspection should verify that the oil heaters are operative.The heaters are insert cartridge type and can bechecked by ammeter reading. They should be energizedwhenever power is available to the control circuit(whenever compressor is inoperative). When the com-pressor starts the heaters are de-energized.

At least once a quarter, all safety controls except com-pressor overloads should be made to operate and theiroperating points checked. Any control may shift itsoperating point as it ages, and this must be detected sothe controls can be readjusted or replaced. Pump in-terlocks and flow switches should be checked to assurethey interrupt the control circuit when tripped.

Contactor in the motor starter should be inspected andcleaned quarterly. Tighten all terminal connections.

The compressor motor resistance to ground should bechecked and logged semi-annually. This log will track in-sulation deterioration. A reading of 5 megohms or less in-dicates possible insulation failure and should be furtherchecked.

The centrifugal compressor must rotate in the directionindicated by the arrow on the casting near the rotationsightglass. If the operator has any reason to suspect thatthe power system connections may have been altered, thecompressor should be jogged to check rotation. Forassistance, call McQuay Service.

CLEANING AND PRESERVINGA common cause of service calls and equipment malfunc-tion is dirt. This can be prevented with normal maintenance.The system components most subject to dirt are:

Permanent or cleanable filters in the air handling equip-ment must be washed in accordance with the manufac-turer’s instructions; throwaway filters should be replaced.The frequency of this service will vary with eachinstallation.

Remove and clean strainers in chilled water system, oilcooler line and condenser water system at everyinspection.


Prior to shutdown periods and before starting again, thefollowing service procedures should be completed.

condenser and chiller water piping should be disconnectedfrom the supply and drained of all water. Dry air blownthrough the condenser will aid in forcing all water out.

ANNUAL SHUTDOWN Removal of condenser heads is also recommended. The1. Where freezing temperatures may be encountered, the condenser and evaporator are not self-draining. Water per-

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mitted to remain in the piping and vessels will rupturethese parts if subjected to freezing temperature.



A dangerous condition can exist if power is applied to a faul-ty compressor motor starter which has been burned out. Thiscondition can exist without the knowledge of the person start-ing the equipment.

Take measures to prevent the shutoff valve in the watersupply line from being accidentally turned on.

If a cooling tower is used and if the water pump will beexposed to freezing temperatures, be sure to remove thepump drain plug and leave it out so that any water whichmay accumulate will drain away.

This is a good time to check all the motor windingresistance to ground. Semi-annual checking and recordingof this resistance will provide a record of any deteriorationof the winding insulation. All new units have well over 100megohms resistance between any motor terminal andground.

Open compressor disconnect switch, and removeFusetrons. If transformer is used for control voltage, thedisconnect must remain on to provide power to oil heater.Set the manual stop/auto switch (SWI) to the stop posi-tion. To insure against the possibility of an accidental start,remove the fault relay from the left side of the MicroTechpanel (see Figure 2, page 4 of IM 403).

Whenever great discrepancies in readings occur or uniformreadings of less than 5 megohms are obtained, the motorcover should be removed for inspection of the winding priorto starting the unit. Uniform readings of less than 5 megohmsindicate motor failure is imminent and motor should be re-placed or repaired. Repair before failure occurs can save agreat deal of time and labor expended in the cleanup of asystem after motor burnout.

Check for corrosion and clean and paint rusted surfaces.1.

Clean and flush water tower for all units operating on awater tower. Make sure tower “blowdown” or bleedoff isoperating. Set up and use a good maintenance programto prevent “liming up” of both tower and condenser. Itshould be recognized that atmospheric air contains manycontaminants which increase the need for proper watertreatment. The use of untreated water may result in cor-rosion, erosion, sliming, scaling or algae formation. It isrecommended the service of a reliable water treatment isrequired-McQuay assumes no responsibility for theresults of untreated or improperly treated water.

The control circuit should be energized at all times. If thecontrol circuit has been off and oil is cool, energize oilheaters and allow 24 hours for heater to remove refrigerantfrom the oil before starting.






Check and tighten all electrical connections.

Replace the drain plug in cooling tower pump if it wasremoved at shutdown time the previous season.

Install Fusetrons in main disconnect switch (if removed).

Reconnect water lines and turn on supply water. Flush outcondenser and check for leaks.

Refer to Service Manual SM001, Centrifugal SystemRemove condenser heads at least once a year and clean Checkout & Start-up information,condenser tubes. energizing the compressor circuit.

and IM 403 before


PUMPING DOWNIf it becomes necessary to pump the system down, extremecare should be used to avoid damage to the water chiller dueto freezing. Always make sure that full water flow is main-tained through the chiller while pumping down. To pumpsystem down, close all liquid line valves. With all liquid linevalves closed and water flowing through chiller, start the com-pressor. Set the MicroTech panel to the manual load (seeIM 403). The vanes must be open while pumping down toavoid a surge or other damaging condition.

Pump the unit down until the mechanical low pressureswitch (MLP) cuts out at 25 psig.

Use a portable condensing unit to complete the pumpdown, condensate the refrigerant, and pump it into thecondenser.

PRESSURE TESTINGNo pressure testing is necessary unless some damage wasincurred. After repairs are made, pressure test the systemat a pressure that does not exceed the standby pressure inthe condenser. (A test pressure higher than condenserpressure would open the discharge check valve and allowflow of test pressure into condenser). In cases where the en-tire refrigerant charge is lost, refer to the following para-graphs. The evacuation procedure can be followed in bothcases.

LEAK TESTINGIn case of the loss of the entire refrigerant charge, the unitshould be checked for leaks prior to charging the completesystem. This can be done by charging only enough refrigerantinto the system to build the pressure up to approximately 10

psig and adding sufficient dry nitrogen to bring the pressureup to a maximum of 125 psig and then leak test with Halideor electronic leak detector. CAUTION: DO NOT USE OXY-GEN TO BUILD UP PRESSURE AS A SERIOUS EXPLO-SION CAN RESULT. A pressure regulating valve shouldalways be used on the drum being used to build the systempressure. Also, do not exceed the test pressure given above.When the test pressure is reached disconnect the gascylinder.

If any leaks are found in welded or silver soldered jointsor if it is necessary to replace a gasket, relieve the testpressure in the system before proceeding. For copper joints,silver solder is recommended.

After making any necessary repair, the system should beevacuated as described below.

EVACUATIONAfter it has been determined that there are no refrigerantleaks, the system should be evacuated using a vacuum pumpwith a capacity of approximately 3 cu. ft/min. and that willreduce the vacuum to at least 1 millimeter (1000 microns).

A mercury manometer, electronic or other type of microngauge should be connected at the farthest point from thevacuum pump. For readings below 1 millimeter, the electronicor other micron gauge should be used.

The triple evacuation method is recommended and is par-ticularly helpful if the vacuum pump is unable to obtain thedesired 1 millimeter of vacuum. The system is first evacuatedto approximately 29 inches of mercury. Enough refrigerantvapor is then added to the system to bring the pressure upto zero gauge pressure. Then the system is once againevacuated to approximately 29 inches of mercury. This is

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repeated 3 times. The second pull down will remove about90% of that remaining from the first pull down and after thethird, only 1110 of 1% non-condensables will remain.

REFRIGERANT CHARGINGThe McQuay centrifugal chillers normally use R-l 2, or R-500refrigerant; therefore, it is recommended that the operatorcheck the unit nameplate to assure the correct refrigerantselection prior to charging or adding refrigerant.

An initial operating charge is made at the factory prior toshipment. In the event the operator needs to add refrigerantafter the unit is installed, certain precautions should be takento protect equipment components. Refrigerant charging linesmust be kept dry, clean and free of non-condensable gases.Care should be taken in selecting the best charging point inthe unit so as to protect the equipment from damage.

If the entire charge is lost or removed from the unit, recharg-ing can be accomplished quickly and safely by introducingthe liquid refrigerant directly into the bottom of the evaporatorwith the expansion valve manually opened. Both condenserwater and chilled water must be flowing through the respec-tive vessels to prevent localized freezing. Consult the chillernameplate for the proper refrigerant charge.

With a near-normal charge in the system, final chargingcan best be accomplished with the unit running with the com-pressor at full load. In this operating mode the unit shouldbe charged until suction superheat is between 2” and 6”F,adjusting the thermal expansion valve as necessary. Con-tinue charging until 9” to 11 “F liquid subcooling is obtainedleaving the condenser if the unit is operating at full load. Atless than full load, liquid subcooling will be proportionally less.

PRESSURE RELIEF VALVE REPLACEMENTCurrent condenser designs use two relief valves (1 set)separated by a three-way shutoff valve. In the event one ofthe relief valves is leaking on the two valve set, the followingprocedures should be followed:

If the valve closest to the valve stem is leaking, back seatthe three-way valve all the way, closing the port to the leak-ing pressure relief valve. Remove and replace the faulty reliefvalve. The three-way shutoff valve should remain either fullyback seated or fully forward for normal operation. If the reliefvalve furthest from the valve stem is leaking, front seat thethree-way valve and replace the relief valve and replace therelief valve as stated above.


Each PEH/PHH centrifugal chiller manufactured by McQuay startup or 18 months from date shipped by the company,carries a standard limited warranty. This warranty covers whichever comes first.repair or replacement of component parts which prove defec- For a complete description of this warranty refer to the war-tive in material or workmanship within 12 months from initial ranty form furnished with the equipment.


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It is important that an air conditioning system receive ade-quate maintenance if the full equipment life and full systembenefits are to be realized.

Maintenance should be an ongoing program from thetime the system is initially started. A full inspection shouldbe made after 3 to 4 weeks of normal operation on a newinstallation and on a regular basis thereafter.

McQuay offers a variety of maintenance servicesthrough its Nationwide Service Organization and can tailorthese services to suit the needs of the building owner.

Most popular among these services is the McQuay Com-prehensive Maintenance Plan wherein McQuay assumesfull responsibility for your air conditioning equipment. In-cluded are regular routine inspections and emergency ser-vice by factory trained technicians. All parts, labor,materials, and refrigerant are included in a McQuay Com-prehensive Maintenance Contract.

For further information concerning the many servicesavailable, contact your local McQuay Service representa-tive.