IntroductionGeneral DescriptionMcQuay type SeasonPak@ air cooled water chillers are com-plete, self-contained automatic refrigerating units that includethe latest in engineering components arranged to provide acompact and efficient unit. Each unit iscompletelyassembled,factory wired, evacuated, charged, -tested and comes com-plete and ready for installation. Each unit consists of multipleair cooled condensers with integral subcooler sections, mul-tiple accessible semi-hermetic single-screw compressors,replaceable tube multiple circuit shell-and-tube evaporator,and complete refrigerant piping. Liquid line componentsincluded are manual liquid lineshutoff valves, charging valves,filter-driers, liquid line solenoid valves, sightglass/moistureindicators, and electronic expansion valves. Other featuresinclude compressor heaters, an evaporator heater for lowambient water freeze protection, automatic one time pumpdownof refrigerant circuit upon circuit shutdown, and an advancedfully integrated microprocessor control system.

The electrical control center includes all safety and oper-ating controls necessary for dependable automatic opera-tion, (the high and low pressure controls and the chiller heaterthermostat are external from the electrical control center.)Thermal overload protected condenser fan motors are fusedin all three conductor legs and started by their own three-polecontactors. Compressors are protected by solid state over-load protection and over temperature protection. Field in-stalled fused disconnect offers additional protection.

Nomenclature

Air cooled m~p

Liquid refrigerant -injected

Screw compressorwater chiller

L Design vintage

Nominal capacity (tons)

InspectionWhen the equipment is received, all items should be carefullychecked against the bill of lading to insure a complete ship-ment. All units should be carefully inspected for damage uponarrival. All shipping damage must be reported to the carrier anda claim must be filed with the carrier. The unit’s serial plateshould be checked before unloading the unit to be sure that

it agrees with the power supply available. Physical damage tounit after acceptance is not the responsibility of McQuayInternational.

Note: Unit shipping and operating weights are available inthe physical data tables on pages 12-l 3.

Page 4 / IM 548

Installation & Start-upNote: Installation and maintenance are to be performed onlyby qualified personnel who are familiar with local codes andregulations, and experienced with this type of equipment.

Figure 1 Suggested pushing arrangementBlocklng Required

ross Full Width

Sharp edges and coil surfaces are a potential injuryhazard. Avoid contact with them.

Start-up by McQuayService is included on all units sold forinstallation within the USA and Canada. Two week priornotification of start-up is required. The contractor should obtaina copy of the Start-up Scheduled Request Form from the salesrepresentative or from the nearest office of McQuayService.

Figure 2a. Suggested lifting arrangement (125 thru 195)

HandlingSpeader barrecommenffed

Care should be taken to avoid rough handling or shock due toimpact or dropping the unit. Do not push or pull the unit fromanything other than the base, and block the pushing vehicleaway from the unit to prevent damage to the sheetmetalcabinet and end frame (see Figure 1).

(Use cautlc,n)

Lift only as shown

Never allow any part of the unit to fall during unloading ormoving as this may result in serious damage.

To lift the unit, 2’/2” (64mm) diameter lifting holes areprovided in the base of the unit. Spreader bars and cablesshould be arranged to prevent damage to the condensercoilsor unit cabinet (see Figures 2a and 2b).

Note:Number of fans may vary from this diagram, but lifting methodremains the same.

Figure 2b. Suggested lifting arrangement (205 thru 280)

Spreader Bars Must Be UsedTo Prevent Cabinet Damage.Locate Bars Above Unit ToClear Fan Grilles. MinimumDistance Across UnitBetween Cables or Chains atBars is 90 Inches. .~

Control Box End

Unit Models ALS 205 thru 280Unit Weights:16,250 Ibs. with Aluminum Fin Coil:18.750 Ibs. with Copper fin Coils

-__‘\/_ “11 (6) Rigging Holes Must BeIS.)Control Box LocationNote: Number of fans can vary from

this diagram, but lifting method

Used (Note

remains the same.Lift Only From (6) Base Points As Shown

IM 548 / Page 5

LocationCare should be taken in the location of the unit to provideproper airflow to the condenser, minimizing effects on con-densing pressure.

Due to the vertical condenser design of the ALS125A thruALS280A chillers, it is recommended that the unit is orientedso that prevailing winds blow parallel to the unit length, thusminimizing the effects of condensing pressure on perfor-mance. If the unit is installed with no protection againstprevailing winds it is recommended that wind baffles beinstalled.

Using less clearances than shown in Figures 3a and 3b willcause discharge air recirculation to the condenser and couldhave a significant and detrimental effect on unit performance.

Service accessEach end of the unit must be accessible after installation forperiodic service work. Compressors, filter-driers, and manualliquid line shutoff valves are accessible on each side of the unitadjacent to the control box. High pressure and low pressuretransducers are mounted on the compressor. The coolerbarrel heater thermostat is located on the cooler. Compressoroverloads, microprocessor, and most other operational, safetyand starting controls are located in the unit control box.

On all ALS units the condenser fans and motors can beremoved from the top of the unit. The complete fan/motorassembly can be removed for service. The fan blade and fanmotor rain shield must be removed for access to wiringterminals at the top of the motor.

Disconnect all power to the unit while servicingcondenser fan motors. Failure to do so may causebodily injury or death.

Figure 3a. Clearance requirements (125 thru 195)

4’.0” Workmg

No ObstructIonsRecommended Area Required

- - - - - - - - - r - - - -

___,r for Unit Operatcon. Air Flow

i

and Maintenance

5,-O” If Open Fenceor 50% Open Wall

I Q-0” It SolId WallClearance per -Natlonal ElectricCode Amcle110-16

_, Er ,-I z’-““)‘n5’Lo” ,f Apen Fence

Swmq r-,-3 or 50% Open Wall6’.0” tf SolId Wall

(See Nqte 3 for Pit)

I 3’.0” Gate orI Opening

Centered onUnit Width

; I

- - - - -1

-_--- -_

+- 2’.0” Mm

F,eldlnsta,led _I L__-______L__-____ ___A

Disconnect Switch. Top View I\Locate so as not to \Block Service Access toUnit Components Air Flow

No ObstructIons Allowed‘r f%c~~~g*~a~l Height

\Above Unit at Any Halght \

i\\

i-

Wall -_ilor Fence I

L

See Note 6

Notes:1. Minimum side clearance between two units is 12 feet.2. Unit must not be installed in a pit or enclosure that is deeper or taller

than the height of the unit unless extra clearance is provided per note 4.3. Minimum clearance on each side is a 8 feet when installed in a pit no

deeper than unit height.4. Minimum side clearance to solid wall or building taller than unit height is

8 feet provided no solid wall above 6 feet tall is closer than 12 feet toopposite side of unit.

5. Removable post for compressor service access must not be blocked ateither side of unit.

6. Do not mount electrical conduits, etc. above the side rail on either sideof unit.

7. There must be no obstruction of the fan discharge.

Page 6 / IM 548

Water pipingDue to the variety of piping practices, it is advisable to followthe recommendations of local authorities. They can supplythe installer with the proper building and safety codes re-quired for a safe and proper installation.

Basically, the piping should be designed with a minimumnumber of bends and changes in elevation to keep systemcost down and performance up. It should contain:

1.

2.

3.

4.

5.

6.

7.

8.

9.

Vibration eliminators to reduce vibration and noisetransmission to the building.Shutoff valves to isolate the unit from the piping systemduring unit servicing.Manual or automatic air vent valves at the high pointsof the system. Drains at the low parts in the system.Some means of maintaining adequate system waterpressure (e.g., expansion tank or regulating valve).Temperature and pressure indicators located at theunit to aid in unit servicing.A strainer or some means of removing foreign matterfrom the water before it enters the pump. It should beplaced far enough upstream to prevent cavitation at thepump inlet (consult pump manufacturer for recommen-dations). The use of a strainer will prolong pump life andthus keep system performance up.A strainer should also be placed in the supply water linejust prior to the inlet of the evaporator. This will aid inpreventing foreign material from entering and decreas-ing the performance of the evaporator.The shell-and-tube cooler has a thermostat and heat-ing cable to prevent freeze-up, due to low ambient,down to -20°F (-28.8”C). It is suggested that theheating cable be wired to a separate 11OV supplycircuit. As shipped from the factory, it is factory wired tothe control circuit. Any water piping to the unit must alsobe protected to prevent freezing.If the unit is used as a replacement chiller on a previ-ously existing piping system, the system should bethoroughly flushed prior to unit installation and thenregular chilled water analysis and chemical watertreat-ment is recommended immediately at equipment start-up.

10.

11.

12.

The total water quantity in the system should be sufficientto prevent frequent “on-off” cycling. A reasonable mini-mum quantity would allow for a complete water systemturnover in not less than 15 minutes.In the event glycol is added to the water system, as anafterthought for freeze protection, recognize that therefrigerant suction pressure will be lower, cooling perfor-mance less, and water side pressure drop greater. If thepercentage of glycol is large, or if propylene is employedin lieu of ethylene glycol, the added pressure drop andloss of performance could be substantial.For operations requiring the ice mode feature, logic inMicroTech will adjust the freezestat to a pressure equiva-lent to 13.5”F (7.5%) below the leaving evaporatorwatertemperature. However, if a different freezestat pressurevalue is desired, thefreezestat can be manually changedthrough MicroTech. Refer to lM549 for additional infor-mation.

If a separate disconnect is used for the 11OV supplyto the cooler heating cable, it should be clearlymarked so that it is not accidentally shut off duringcold seasons.

Prior to insulating the piping and filling the system, a prelimi-nary leak check should be made.

Piping insulation should include a vapor barrier to preventmoisture condensation and possible damage to the buildingstructure. It is important to have the vapor barrier on theoutside of the insulation to prevent condensation within theinsulation on the cold surface of the pipe.

Figure 7. Typical field water piping

Valve Valve

IM 548 / Page 9

Flow switch Glycol solutionsA water flow switch must be mounted in eitherthe entering orleaving water line to insure that there will be adequate waterflow to the evaporator before the unit can start. This willsafeguard against slugging the compressors on start-up. Italso serves to shut down the unit in the event that water flowis interrupted to guard against evaporator freeze-up.

The system glycol capacity, glycol solution flow rate, andpressure drop through the cooler may be calculated using thefollowing formulas and tables.

A flow switch is available from McQuay under orderingnumber 0017503300. It is a “paddle” type switch and adapt-able to any pipe size from 1” (25mm) to 8” (203mm) nominal.Certain minimum flow rates are required to close the switchand are listed in Table 4. Installation should be as shown inFigure 8.

Note: The procedure below does not specify the type ofglycol. Use the derate factors found in table 5 for correctionswhen using Ethylene glycol and those in table 6 for Propyleneglycol.

Electrical connections in the unit control center should bemade at terminals 62 and 63. The normally open contacts ofthe flow switch should be wired between these two terminals.Flow switch contact quality must be suitable for 24 VAC, lowcurrent (16ma). Flow switch wire must be in separate conduitfrom any high voltage conductors (115 VAC and higher).

Capacity - Cooling capacity is reduced from that withplain water. To find the reduced value multiply the chiller’swater system tonnage by the capacity correction factor tofind the chiller’s capacity in the glycol system.

Flow -To determine flow (or delta-T) knowing delta-T (orflow) and cap:

Glycol flow = 24 x cap (Glycol) x flow factordelta-T

Table 4. Flow switch minimum flow rates

Pressure drop - To determine pressure drop through thecooler, when using glycol, enter the water pressure dropgraph on page 11 at the actual glycol flow. Multiply thewater pressure drop found there by the PD factor to obtaincorrected glycol pressure drop.

To determine glycol system kW, multiply the water systemkW by factor called Power.

Note: Water pressure differential switches are not recommended for outdoorapplications.

Figure 8. Flow switch

Flow Direction Marked on

1 .OO NPT Flow Switch

5 Pipe Dia. - MinlmumAfter Switch

5 Pipe Dia. - MinimumBefore Switch

Water connectionsWater piping to the cooler can be brought up through thebottom of the unit or through the side between the verticalsupports. The dimensional data on pages 15 and 16 gives thenecessary dimensions and locations for all piping connections.

Note: On unit size 175A thru 195A there is a diagonalbrace off of a vertical support which will interfere with thewater connection if brought in from the side. This brace canbe removed, but only after the unit is in place.

Refrigerant chargeAll units are designed for use with HCFC-22 and are compat-ible with HCFC alternatives and are shipped with a fulloperating charge. The operating charge for each unit isshown in the Physical Data Tables on pages 12 and 13.

Test coolantwith a clean, accurate glycol solution hydrometer(similar to that found in service stations) to determine thefreezing point. Obtain percent glycol from the freezing pointtable below. On glycol applications it is normally recom-mended by the supplier that a minimum of 25% solution byweight be used for protection against corrosion.

Do not use an automotive grade antifreeze. Indus-trial grade glycols must be used. Automotive anti-freeze contains inhibitors which will cause platingon the copper tubes within the chiller evaporator.Thetypeand handling of glycol used must be consis-tent with local codes.

Table 5. Ethylene glycol

I I I

40 1 - 7 1 -22 1 0.961 1 0.976 1 1.121 [ 1.263

50 1 -28 1 -33 1 0.946 1 0.966 1 1.178 1 1.308

Table 6. Propylene glycol

Page 10 / IM 548

Evaporator water flow andpressure dropBalance the chilled water flow through the evaporator. Theflow rates must fall between the minimum and maximumvalues shown in Table 7. Flow rates below the minimumvalues shown will result in laminar flow which will reduceefficiency, cause erratic operation of the electronic expan-sion valve and could cause low temperature cutouts. On theother hand flow rates exceeding the maximum values showncan cause erosion on the evaporator water connections andtubes.

Measure the chilled water pressure drop through theevaporator at field installed pressure taps. It is important notto include valves or strainers in these readings.

Variable chilled water flow through the evaporator whilethe compressor(s) are operating is not recommended.MicroTech control set points are based upon a constant flowand variable temperature.

Evaporator water pressure drop

Flow (LPS)

Table 7. Min/max evaporator flow rates

ALS UNIT &T&J. PLO% MT’E %4&X. FLOW RATESIZE am 1 w wm I b125 186 1 11.8 497 I 31.4

140 209 13.2 557 35.2

155 231 14.6 617 39.0

170 253 16.0 675 42.7

175 256 16.2 683 43.2

185 274 17.3 730 46.1

195 284 18.0 767 48.5

205 309 19.5 625 52.1

220 335 21.2 893 56.4

235 356 22.5 950 60.0

250 376 23.6 1000 63.2

265 391 24.7 1043 66.0

280 408 25.8 1088 68.8

10 15 20 25 30 40 50 60

100 200 300 400 600 800 1000

Flow (GPM)

IM 548 / Page 11

Field Wiring

GeneralWiring must comply with all applicable codes and ordinances.Warranty is voided if wiring is not in accordance with specifica-tions. An open fuse indicates a short, ground, or overload.Before replacing a fuse or restarting a compressor or fanmotor, the trouble must be found and corrected.

Copper wire is required for all power lead terminations atthe unit and copper must be used for all other wiring to the unit.

ALS units may be ordered with main power wiring for eithersingle or multiple point power connection. If single point powerconnection is ordered, a single large power terminal block isprovided and wiring within the unit is sized in accordance withthe National Electrical Code. A single field supplied disconnectis required. An optional factory mounted transformer for the115 volt control circuit may be provided.

If multiple point powerwiring is ordered, two power connec-tions (125 thru195) or three power connections (205 thru 280),one per compressor circuit including condenser fans, arerequired and wiring within the unit is sized in accordance withthe National Electrical Code. A separate circuit is required forthe 115 volt control circuit Separate field supplied disconnectsare required for each electrical circuit.

It may be desirable to have the unit cooler heater on aseparate disconnect switch from the main unit power supply sothat the unit may be shut down without defeating the freezeprotection provided by the cooler heater.

ALS unit compressors are single direction rotationcompressors. For this reason proper phasing ofelectrical power is important. Electrical phasing mustbe A, B, C for electrical phases 1, 2 and 3(A=L1 ,B=L2,C=L3). Units supplied with single pointfactory power connections will include oneMotorSaver@ phase failure, phase reversal protec-tive device that will prevent operation of the unit withincorrect power phasing. The MotorSaver is factorywired and tested. Do not alter the wiring to theMotorSaver. JMultiple point power wired units will include two (125 thru

195) or three (205 thru 280) MotorSaver safety controls (onefor each power supply), and the contractor is cautioned to notapplypoweruntilthephasing isverifiedwith aphasesequencemeter.

Internal power wiring to the compressors for thesingle point versus the multiple point option are

installed according to the way the unit is built.

IM 548/ Page 17

Electrical data notes:

1. Allowable Voltage Limits:Unit nameplate 208Vi60Hzl3PH: 187V to 229VUnit nameplate 230Vl60Hzl3Ph: 207V to 253VUnit nameplate 380V/60Hz/3Ph: 342V to 418VUnit nameplate 460V/60Hz/3Ph: 414V to 506VUnit nameplate 575V/60Hz/3Ph: 517V to 633VUnit nameplate 415V/50Hz/3Ph: 373V to 457VUnit nameplate 380Vl50HzJ3Ph: 342V to 418V

2. Unit wire size ampacity (MCA) is equal to 125% of the largest compressor-motor RLA plus 100% of RLA of all other loadsin the circuit including control transformer. Wire size ampacity for separate 115V control circuit power is 15 amps forALS125A through ALS280A.

3. Compressor RLA values are for wire sizing purposes only but do reflect normal operating current draw at unit rated capacity.If unit is equipped with SpeedTrol condenser fan motors, the first motor on each refrigerant circuit is a single phase, 1 hpmotor, with a FLA of 2.8 amps at 460 volts (5.6 amps at 208/230 volts). If the unit is not equipped with SpeedTrol, the standardfan motor will be 1% hp, 3-phase with a FLA as shown in the electrical tables.

4. Compressor LRA for reduced inrush start is for the first winding. If the unit is equipped with SpeedTrol motors, the first motoron each refrigerant circuit is a single phase, 1 hp motor, with a LRA of 7.3 amps at 460 volts (14.5 amps at 208/230 volts).If the unit is not equipped with SpeedTrol, the standard fan motor will be 1% hp, 3-phase with a LRA as shown in the electricaltables.

5. Single point power supply requires a single disconnect to supply electrical power to the unit. This power must be fused.

6. Multiple point power supply requires two independent power circuits on ALS125A thru ALS195A and three independentpower circuits on ALS205A thru ALS280A each with separate fused disconnects and a separate control circuit.

7. All field wiring to unit power block or optional nonfused disconnect switch must be copper.

8. All field wire size values given in tables apply to 75°C rated wire per NEC.

9. Disconnect switches must be field supplied

10. All wiring must be done in accordance with applicable local and national codes.

IM 548 / Page 29

Electrical legend

ABRESI,RESPADICl-C3Cll,C21CBI-CBGCB9CBIOCHWICOMPR l-3CSII-cs33CTI.CTPDSl ,DS2EXVFIF2FB5FB6-FBI5GDI-GD3G F PGRD.GNDHTRI-HTR3HTRSJI.Jl3JB5KEYPADLPSI-LPS3MI-M6MI-M37MC0250MHPRI-MHPRJMJMODEMIMODEM2MPRI-MPRJMTRJI-MTR37NBOBOLI-OL6051.OS3PBI-PB3PSI-PS3PVMI-PVM3

ALARM BELL

ANALOG DIGITAL INPUT BOARDSURGE CAPACITOR. COMPRESSORCAPACITOR, SPEEDTROL

RESISTOR. CURRENT TRANSFORMER

CIRCUIT BREAKER (POWER]CIRCUIT BREAKER (MICROTECH)CIRCUIT BREAKER [FAX ALARM)CHILLED WATER INTERLOCKCOMPRESSORSI-3COMPRESSOR SOLENOIDCURRENT TRANSFORMERDISCONNECT SWITCH, MAINELECTRONIC EXPANSION VALVEFUSE, CONTROL CIRCUITFUSE, COOLER HEATERFUSEBLOCK. CONTROL POWERFUSEBLOCKS, FAN MOTORSGUARDISTOR RELAYGROUND FAULT PROTECTORG R O U N DCOMPRESSOR HEATERHEATER,EVAPORATORJUMPERS (LEAD)JUNCTION BOX, EVAP. HEATERKEYPAD SWITCH & DISPLAYLIQUID PRESENCE SENSORCONTACTORS, COMPRESSORCONTACTOR, FAN MOTORSMICROTECH CONTROL BOARD-250MECH. HIGH PRESSURE RELAYMECHANICAL JUMPERMODEM, MICROTECHMODEM, FAXMOTOR PROTECTOR RELAYMOTORS, CONDENSER FANSNEUTRAL BLOCKOUTPUT BOARD, MICROTECHOVERLOADSOIL SAFETY SWITCHPOWER BLOCK, MAINPUMPDOWN SWITCHESPHASE VOLTAGE MONITOR

CTRL BOX, CTRL PANEL

BACK OR SIDE OF CTRL BOX

CTRL BOX, POWER PANELINSIDE SPEEDTROL BOX

CTRL BOX, POWER PANEL

CTRL BOX, POWER PANELCTRL BOX, CTRL PANELCTRL BOX, CTRL PANELFIELD INSTALLEDON BASE RAILON COMPRESSORCTRC BOX, POWER PANELCTRL BOX, POWER PANELCTRL BOX, CTRL PANELCTRL BOX, SWITCH PANELCTRL BOX, SWITCH PANELCTRL BOX, POWER PANELCTRL BOX, POWER PANELCTRL BOX, CTRL PANELCTRL BOX, POWER PANELCTRL BOX, POWER PANELON COMPRESSORSWRAPPED AROUND EVAPCTRLBOX, CTRLPANELNEAR EVAP, ON BASE RAILCTRL BOX, KEYPAD PANELON COMPRESSORCTRLBOX, POWERPANELCTRL BOX, POWER PANELCTRL BOX, CTRL PANELCONTROL BOX, CTRL PANELCTRL BOX, CTRL PANELCTRL BOX, CTRL PANELCTRL BOX, CTRL PANELCONTROL BOX, CTRL PANELCONDENSER SECTIONCTRL BOX, CTRL PANELCTRL BOX, CTRL PANELCTRL BOX, POWER PANELCTRL BOX, CTRL PANELCTRL BOX, POWER PANELCTRL BOX, SWITCH PANELCTRL BOX, POWER

Evaporator freeze protectionAll heat exchangers come equipped with thermostaticallycontrolled heat tape. When power is applied to terminals 13and 16, the heat tape will provide freeze protection down to-20°F (-28.8%). However, this should not be the only methodof freeze protection. Unless the evaporator is flushed anddrained as is described below in note 4 two or more of theremaining 3 recommendations must be followed as part of thesystem design:1. By continuous circulation of water through the piping and

the heat exchanger.2. By the inclusion of glycol solution in the chilled water circuit,3. By the addition of insulation, and heat during cold weather,

RESl.RES2 RESISTOR. CURRENT TRANSFORMER CTRL BOX, POWER PANEL-SI SWITCH, MANUAL START/STOP CTRL BOX, KEYPAD PANELSCII.SCPi.SC31 S P E E D C O N T R O L INSIDE SPEEDTROL BOXSIG CONV(SC)SVI.SVZ.SV7SV3SV4,Sw3SV5,SV6,SV9TlT2, T5T3

T4.T6TIO

TB2TB3TB4-TB6787

TB9TBIOTD5-TD7

SIGNAL CONVERTER CTRL BOX, CTRL PANELSOLENOID VALVE, LIQ. LINES ON LIQUID LINESSOLENOID VALVE, LIQ INJECTION ON COMPR LIQ. INJ. LINESOLENOID VALVE, HG BYPASS ON LINE TO HOT GAS VALVETRANSFORMER, MAIN CONTROL CTRL BOX, POWER PANELTRANSFORMER, 120 TO 24V CONTROL CTRL BOX, CTRL PANELTRANSFORMER, 575 TO 208.230V CTRL BOX, CTRL PANEL

SPEEDTROLTRANSFORMER, 24 TO 18V CONTROL CTRL BOX, CTRL PANELTRANSFORMER, 208-240 TO 24V OR CTRL BOX, CTRL PANEL

460 TO 24V -SPEEDTROLTERMINAL BLOCK, 12OV FIELD CTRL BOX, CTRL PANELTERMINAL BLOCK, 24V FIELD CTRL BOX, CTRL PANELTERMINAL BLOCK, CONTROL CTRL BOX, CTRL PANELTERM1 14AL BLOCK, FIELD CONN CTRL BOX, CTRL PANEL(LESS THAN 24V ONLY)

TERMINAL BLOCK, MICROTECH ONLY CTRL BOX, CTRL PANELTERMlNAL BLOCK, FAX ALARM CTRL BOX, CTRL PANELTlME DELAY. COMPR. REDUCED INRUSH CTRL BOX, CTRL PANEL

- POWER WIRING, FACTORY INSTALLED

- - - P O W E R W I R I N G , F A C T O R Y I N S T A L L E D

~~ ~~ ~~ POWER WIRING, FACTORY INSTALLED

/@f CONTROL BOX TERMINAL, FIELD CONN. USAGE

@ CONTROL BOX TERMINAL, FACTORY USAGE

. UNINDENTIFIED C O M P O N E N T T E R M I N A L

0 INDENTIFIEDCOMPONENTTERMINAL

0 WIRE NUT

@ MANUAL RESET, C.ONTROL

+ AUTOMATIC RESET, CONTROL

F_m/: CABLE-TWISTED

SHIELDED ANDJACKETED PAIR

THERMISTOR

+ D I O D E

+ t C A P A C I T O R

E VARISTOR‘V

to the exposed piping and heat exchanger.4. By draining and flushing the chillervessel with glycol during

subfreezing weather.Figure 12 shows typical field wiring that is required for unit

installation. On models ALS125A through 280A the time clockis connected between terminals 60 and 61.

It is the responsibility of the installing contractor and/or on-site maintenance personnel to insure that this additional pro-tection is provided. Routine checks should be made to insureadequate freeze protection is maintained.

Failure to do so may result in damage to unit components.Freeze damage is not considered a warranty failure.

Page 30 / IM 548

Unit Layout and Principles of Operation

Major component locations

Figure 10. Component locations (125A thru 195A)

Top of Unit

Figure 11. Component locations (205A thru 280A)

t-Condenser Circuit #1 -_j t- Condenser Ci rcu i t #3 -1

,@(EJ@@@@ ‘@@@

@zJ@@@@@ -@@@

t C o n d e n s e r C i r c u i t #2 Pj -L- Condenser Circuit #3

Control centerAll electrical controls are enclosed in a weather resistant control The low voltage components are located on the left sidecenter with keylocked, hinged access doors. The control center with the 115 VAC terminals located behind the deadfrontis composed of two separate compartments, high voltage andlow voltage. All of the high voltage components are located in

panel. This protects service personnel from 115 VAC termi-nals when accessing the adjustable and resettable controls.

the compartment on the right side of the unit.

Page 32 / IM 548

Sequence of operationThe following sequence of operation is typical for McQuaymodels ALS125A through ALS280A screw water chillers. Thesequence may vary depending on the software revision orvarious options which may be installed on the chiller.

Off conditionsWith power supplied to the unit, 115 VAC power is appliedthrough the control fuse F1 to the compressor heaters (HTR1 ,HTR2, HTR3 and evaporator heater) and the primary of the24V control circuit transformer. Note: Compressor heatersmust be on for at least 12 hours prior to start-up. The 24Vtransformer provides power to the MicroTech controller andrelated components. With 24V power applied, the controllerwill check the position of the front panel system switch. If theswitch is in the “stop” position the chillerwill remain off and thedisplay will indicate the operating mode to be OFF: SystemSW. The controller will then check the pumpdown switches. Ifany of the switches is in the “stop” position, that circuit’soperating mode will be displayed as OFF: PumpDwnSw. Ifthe switches for both circuits are in the “Stop” position the unitstatus will display OFF: PumpdownSw’s. If the remote start/stop switch is open, the chiller will be OFF: RemoteSw. Thechiller may also be commanded off via communications froma separate communicating panel such as the Remote Moni-toring and Sequencing Panel or an Open Protocol interface.The display will show OFF: RemoteComm if this operatingmode is in effect. If an alarm condition exists which preventsnormal operation of both refrigerant circuits, the chiller will bedisabled and the display will indicate OFF:. Alarm. If thecontrol mode on the keypad is set to “Manual Unit Off,” thechiller will be disabled and the unit status will display OFF:ManualMode. Assuming none of the above stop conditionsare true, the controller will examine the internal time scheduleto determine whether the chiller should be permitted to start.The operating mode will be OFF: TimeClock if the timeschedule indicates time remaining in an “off” time period.

AlarmThe alarm light on the front panel will be illuminated when oneor more of the cooling circuits has an active alarm conditionwhich results in the circuit being locked out of operation.Unless the alarm condition affects all circuits the remainingcircuits will operate as required. Refer to IM 549 for additionaldetails.

Start-upIf none of the above “off” conditions are true, the MicroTechcontroller will initiate a start sequence and energize thechilled water pump output relay. The chiller will remain in theWaitForFlow mode until the field installed flow switch indi-cates the presence of chilled water flow. If flow is not provenwithin 30 seconds, the alarm output will be turned on, thekeypad display will be WaitForFlow and the chiller willcontinue to wait for proof of chilled water flow. Once flow isestablished, the controller will sample the chilled water tem-perature and compare it against the Leaving Chilled WaterSetpoint, the Control Band, and the Start-up Delta Tempera-ture, which have been programmed into the controller’smemory. If the leaving chilled water temperature is above theLeaving Chilled Water Setpoint plus % the Control Band plusthe adjustable Start-up Delta Temperature, the controller will

select the refrigerant circuit with the lowest number of startsas the lead circuit and energize the first stage of the CoolStaging mode. The controller will start the compressor andenergize the compressor liquid injection solenoid along withthe main liquid line solenoid. The controller will deiay theopening of the electronic expansion valve until the evaporatorpressure decreases to a preset value. This is the evaporatorprepurge mode and the display will show Pre-Purge. Thevalve will then open allowing refrigerant to flow through theexpansion valve and into the evaporator and the display willshow Opened EXV. If additional cooling capacity is required,the controller will energize the additional cooling capacity byactivating the first compressor’s capacity control solenoids.As the system load increases, the controller will start the lagrefrigerant circuit in the same manner after interstage timersare satisfied. The compressors and capacity control sole-noids will automatically be controlled as required to meet thecooling needs of the system. The electronic expansion valvesare operated by the MicroTech controller to maintain preciserefrigerant control to the evaporator at all conditions.

Condenser controlThe first condenser fan stage will be started along with thefirst compressor to provide initial condenser head pressurecontrol. The MicroTech controller will activate the remainingcondenser fans as needed to maintain proper condenserpressure. The MicroTech controller continuously monitorsthe condenser minus evaporator lift pressure and will adjustthe number of operating condenser fans as required. Thenumber of condenser fans operating will vary with outdoortemperature and system load. The condenser fans arematched to the operating compressors so that when a com-pressor is off all fans for that circuit will also be off. On unitswith the fan speed control option (SpeedTrol) the lead fan oneach circuit wi l l vary in speed to maintain condenser pressureat lower outdoor temperatures.

PumpdownAs the system chilled water requirements diminish, the com-pressors will be unloaded. As the system load continues todrop, the electronic expansion valves will be stepped closedand the refrigerant circuits will go through a pumpdownsequence. As the evaporator pressure falls below thepumpdown pressure setpoint while pumping down, thecompressor(s) and condenser fans will stop. The unit has aone time pumpdown control logic; therefore, if the evaporatorpressure rises while the refrigerant circuit is in a pumpdownmode, the controller will not initiate another pumpdown se-quence. The controller will keep the unit off until a call forcooling occurs. Refer to the pumpdown control section in IM549for additional details. The chilled water pump output relaywill remain energized until the time schedule’s “on” timeexpires, the remote stop switch is opened, the system switchis moved to the stop position, or a separate communicationspanel such as the Remote Monitoring and Sequencing Panelor an Open Protocol interface deactivates the chilled waterpump output.

Page 34 / IM 548

Start-up and Shutdown

Pre start-up

To assure correct compressor rotation, field powersupply leads must be properly phased prior to start-up*

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

With all electric disconnects open, check all screw or lugtype electrical connections to be sure they are tight forgood electrical contact.Inspect all water piping for flow direction and correctconnections at the evaporator.Using a phase tester, check that electrical phasing toeach compressor circuit is A-B-C for phases L1 , L2, & L3respectively.Check the voltage of the unit power supply and see that itis within the &lo% tolerance that is allowed. Voltageunbalance between phases must be within +3%.Check the unit power supply wiring for adequate ampac-ityand a minimum insulation temperature rating of 75°C.Verify that all mechanical and electrical inspections havebeen completed per local codes.See that all auxiliary control equipment is operative andthat an adequate cooling load is available for initial start-up.Check all compressor valve connections for tightness toavoid refrigerant loss at start-up. Although all factoryconnections are tight before shipment, some looseningmay have resulted from shipping vibration. Open thecompressor suction and discharge shutoff valves untilbackseated. Open the liquid line shutoff valves untilbackseated. Always replace valve seal caps.Make sure system switch S1 is in the “Stop” position andpumpdown switches PS1, PS2 and PS3 are on“Pumpdown and Stop,“throw the main power and controldisconnect switches to “on.“ This will energize crankcaseheaters. Wait a minimum of 12 hours before starting upunit, Turn compressor circuit breakers to “off” positionuntil ready to start unit.Vent the air from the evaporator as well as from thesystem piping. Open all water flow valves and start thechilled water pump. Check all piping for leaks. Flush theevaporator and system piping to obtain clean, noncorro-sive water in the evaporator circuit.

Most relays and terminals in the unit control centerare powered when S1 is closed and the controlcircuit disconnect is on. Therefore do not close S1until ready for start-up.

Initial start-up must be performed by McQuaySer-vice personnel. Don’t proceed with start-up untillM549 has been read.

Start-up1. Doublecheckthatthecompressorsuction anddischarge

shutoff valves are backseated. Always replace valveseal caps.

2. Insure that the ball valves are open on the lines enteringthe evaporator.

3. Insure that the manual liquid line shutoff valve at theoutlet of the subcooler is open.

4.

5.

6.

7.

8.

9.

10.

11.

Adjust the leaving chilled water temperature setpoint onthe MicroTech controller to the desired chilled watertemperature. The control band is preset for 10 degreesDelta-T between the entering and leaving evaporatorwater temperature at full load. If the Delta-T is outside an8”-12”Frange, at full load, resetthecontrol bandaspertheinstructions found in the MicroTech IM Manual 549.Start the auxiliary equipment for the installation by turn-ing on the time clock, and/or remote on/off switch, andchilled water pump.Check to see that pumpdown switches PS1, PS2 andPS3 are in the “Pumpdown and Stop” (open) position.Throw the S1 switch to the “auto” position.Under the “Control Mode” menu of the keypad place theunit into the automatic cool mode.Start the system by moving pumpdown switch PS1 to the“auto” position.After running circuit 1 for a short time, check the rotationof the condenser fans. (Proper rotation will have air beingdrawn into the vertical coils and discharged out the top ofthe unit.) Check for flashing in the refrigerant sightglassunder stable conditions.Repeat steps 8 and 9 for PS2 and PS3 and the secondand third refrigerant circuits.Superheat is factory adjusted to maintain between 6”and 12°F.

Caution: The superheat should be between 6” and12”F, with the liquid line sightglass full, once thesystem temperatures have stabilized at theMicroTech setpoint temperatures.

12. After system performance has stabilized, it is necessarythat the “Compressor Equipment Warranty Form” becompleted to obtain full warranty benefits. This form isshipped with the unit, and after completion, should bereturned to McQuayService through your sales repre-sentative.

Temporary shutdownMove pumpdown switches PS1, PS2 and PS3 to the“Pumpdown and Stop” position. After the compressors havepumped down, turn off the chilled water pump. Caution: DOnot turn the unit off using the "S1" switch, without firstmoving PS1, PS2 and PS3 to the “Stop” position, unlessit is an emergency as this will prevent the unit from goingthrough a pumpdown.

The unit has one time pumpdown operation. WhenPS1, PS2 and PS3 are in the “Pumpdown and Stop”position the unit will pumpdown once and not runagain until the PS1, PS2 and PS3 switches are movedto the auto position. If PSI, PS2 and PS3 are in theauto position and the load has been satisfied the unitwill go into one time pumpdown and will remain offuntil MicroTech senses a call for cooling and startsthe unit.

must not be cycled off by usingthe evaporator pump or the disconnect switch.

Page 36 / IM 548

It is important that the water flow to the unit is not inter-rupted before the compressors pumpdown to avoid freeze-upin the evaporator.

If all power is turned off to the unit the compressor heaterswill become inoperable. Once power is resumed to the unit itis important that the compressor heaters are energized aminimum of 12 hours before attempting to start the unit.Failure to do so could damage the compressors due toexcessive accumulation of liquid in the compressor.

Start-up after temporary shutdown1. Insure that the compressor heaters have been energized

for at least 12 hours prior to starting the unit.2. Start the chilled water pump.3. With System switch S1 in the”on” position, move pumpdown

switches PSI, PS2 and PS3 to the “auto” position.4. Observe the unit operation until the system has stabilized.

.

If shutdown occurs or will continue through periodsbelow freezing ambient temperatures, protect the

Extended shutdown1.

2.

3.4.5.

6.

7.

8.

Move the PS1, PS2 and PS3 switches to the manualpumpdown position.After the compressors have pumped down, turn off thechilled water pump.Turn off all power to the unit and to the chilled water pump.Move the emergency stop switch S1 to the “off” position.Close the compressor suction and discharge valves aswell as the liquid line shutoff valves.Tag all opened disconnect switches to warn against start-up before opening the compressor suction and dischargevalves and liquid line shutoff valves.If glycol is not used in the system drain all water from theunit evaporator and chilled water piping if the unit is to beshut down during winter. Do not leave the vessels orpiping open to the atmosphere over the shutdownperiod.Leave power applied to the cooler heating cable if aseparate disconnect is used.

System Maintenance

General Electrical terminalsOn initial start-up and periodically during operation, it will benecessary to perform certain routine service checks. Amongthese are checking the liquid line sightglasses and takingcondensing and suction pressure readings. Through theMicroTech keypad, check to see that the unit has normalsuperheat and subcooling readings.

Electric shock hazard. Turn off all power beforecontinuing with following service.

A Periodic Maintenance Log is located on page 51 of thismanual. It is suggested that the report be completed on amonthly basis. The log will serve as a useful tool for a servicetechnician in the event service is required.

All power electrical terminals, for compressors and fanmotor power wiring, should be retightened every six months,as they tend to loosen in service due to normal heating andcooling of the wire.

Compressor maintenanceCondensers

Since the compressor is semi-hermetic requiring no oil sepa-rator, oil heaters and pumps, no yearly maintenance is nor-mally required. However, vibration is an excellent check forproper mechanical operation. Compressor vibration is anindicator of the requirement for maintenance and contributesto a decrease in unit performance and efficiency. It is recom-mended that the compressor be checked with a vibrationanalyzer at or shortly after start-up and again on an annualbasis, When performing the test the load should be maintainedas closely as possible to the load of the original test. Thevibration analyzer test provides a fingerprint of the compressorand when performed routinely can give a warning of impendingproblems. The compressor is checked at the factory for maxi-mum vibration of 0.14 IPS (3.56 mm/s) at 3600 rpm.

The compressor is supplied with a lifetime oil filter. It is agood policy to replace this filter anytime the compressor isopened for servicing.

Fan motor bearings

Condensers are air cooled and constructed with 3/8” (9.5mm)O.D. internally finned copper tubes bonded in a staggeredpattern into slit aluminum fins. No maintenance is ordinarilyrequired except the occasional removal of dirt and debris fromthe outside surface of the fins. McQuay recommends the useof foaming coil cleaners available at air conditioning supplyoutlets. Use caution when applying such cleaners as theymay contain potentially harmful chemicals. Care should betaken not to damage the fins during cleaning. If the servicetechnician has reason to believe that the refrigerant circuitcontains noncondensables, manual purging may be required.The purge Shradervalve is located on the vertical coil headeron both sides of the unit at the control box end of the coil.Access panels are located at the end of the condenser coildirectly behind the control panel. Purge with the unit off, aftershutdown of 1 5 minutes or longer, to allow air to collect at thetop of the coil. Restart and run the unit for a brief period. Ifnecessary shut unit off and repeat the procedure. Followaccepted environmentally sound practices when removingrefrigerant from the unit.

The fan motor bearings are of the permanently lubricatedtype. No lubrication is required. Excessive fan motor bearingnoise is an indication of a potential bearing failure.

Refrigerant sightglassThe refrigerant sightglasses should be observed periodically.(A weekly observation should be adequate.) A clear glass ofliquid indicates that there is adequate refrigerant charge in thesystem to insure proper feed through the expansion valve.Bubbling refrigerant in the sightglass, during stable run con-ditions, indicates that the system may be short of refrigerant

IM 548 / Page 37

charge. Refrigerant gas flashing in the sightglass could alsoindicate an excessive pressure drop in the liquid line, possiblydue to a clogged filter-drier or a restriction elsewhere in theliquid line. If subcooling is low add charge to clear thesightglass. If subcooling is normal (1 O”-15°F) and flashing isvisible in the sightglass check the pressure drop across thefilter-drier.

An element inside the sightglass indicates the moisturecondition corresponding to a given element color. If thesightglass does not indicate a dry condition after about 12hours of operation, the unit should be pumped down and thefilter-driers changed.

Lead-lagA feature on all McQuay ALS air cooled chillers is a system foralternating the sequence in which the compressors start tobalance the number of starts and run hours. Lead-Lag of therefrigerant circuits is accomplished automatically through theMicroTech Controller. When in the auto mode the circuit withthe fewest number of starts will be started first. If all circuits areoperating and a stage down to one circuit is required, the circuitwith the most operating hours will cycle off first. The operatormay override the MicroTech controller, and manually selectthe lead circuit as circuit #1, #2 or circuit #3.

Service

Service on this equipment is to be performed byqualified refrigeration personnel familiar with equip-ment operation, maintenance, correct servicing pro-cedures, and the safety hazards inherent to thiswork. Causes for repeated tripping of safety controlsmust be investigated and corrected.

Disconnect all power before doing any service insidethe unit.

Anyone servicing this equipment shall comply withthe requirements set forth by the EPA in regards torefrigerant reclamation and venting.

Compressor solenoidsThe ALS unit screw compressors are equipped with 3 sole-noids to control compressor unloading. The solenoids arecontrolled by MicroTech outputs. See unit wiring diagrams.The solenoids are energized at various compressor loadconditions as indicated in the table below.

Table 24.

Location of the solenoids is as follows:The top solenoid is on top of the compressor near the

discharge end.The bottom solenoids are on the lower side of the compres-

sor on the opposite side from the terminal box. The bottom frontsolenoid is the one closest to the discharge end of the com-pressor. The bottom rear solenoid is the one closest to themotor end of the compressor.

If the compressor is not loading properly check the sole-noids to see if they are energized per the above chart. Acomplete check will include a check of the MicroTech output,the wiring to the solenoid and the solenoid coil itself.

Filter-driersA replacement of the filter-drier is recommended duringscheduled service maintenance of the unit, any time exces-sive pressure drop is read across the filter-drier and/or whenbubbles occur in the sightglass with normal subcooling. Apartially clogged filter can also cause trips on the no liquid runsensor. The maximum recommended pressure drop acrossthe filter-drier at 75% to 100% circuit loading is 10 psig (69 kPa).The maximum recommended pressure drop across the filter-drier at 25% to 50% circuit loading is 5 psig (34.5 kPa).

The filter-drier should also be changed if the moistureindicating liquid line sightglass indicates excess moisture bythe wet system color indicators.

During the first few months of operation the filter-drierreplacement may be necessary if the pressure drop acrossthe filter-drier exceeds the values listed in the paragraphabove. Any residual particles from the unit heat transfertubing, compressor and miscellaneous components are sweptby the refrigerant into the liquid line and are caught by thefilter-drier.

--

The following is the procedure for changing the filter-driercore:

This procedure is slightly different from a typical recipro-cating compressor unit due to the use of a liquid injectionfeature on the ALS screw compressor unit. Anytime thecompressor contactor is closed liquid from the liquid line isinjected into the screw for cooling and sealing. This liquidinjection also occurs during normal pumpdown and limits howlow a pumpdown can be achieved.

The standard unit pumpdown is set to stop pumpdownwhen 34 psig (235 kPa) suction pressure is reached. To fullypump down a circuit beyond 34 psig (235 kPa) for servicepurposes a “Full Pumpdown” service mode can be activatedusing the keypad. Go to the “Alarm Spts” Menu on theMicroTech keypad, step through the menu items until“FullPumpDwn” is displayed. Change the setting from “No” to“Yes”.

The next time either circuit is pumped down, thepumpdownwill continue until the evaporator pressure reaches 2 psig(14 kPa) or 60 seconds have elapsed, whichever occurs first.Upon completing the pumpdown, the “FullPumpDwn” setpointis automatically changed back to “No”.

The procedure to perform a full service pumpdown forchanaina the filter-drier core is as follows.

Perform a normal pumpdown to 34 psig (235 kPa) bymoving the pumpdown switch to the“Pumpdown” position.This step will pump down the evaporator with compressorliquid injection still active.Close the liquid line shutoff valve above the filter-drier,on the circuit to be serviced.Under the “Alarm Spts”, change the “FullPumpDwn”setpoint from “No” to “Yes”.

Page 38 / IM 548

4.

5.

6.

The circuit status should be “0ff:PumpDwnSw”. Move thecircuit pumpdown switch from “Pumpdown and Stop” to“Auto”. Also clear the anticycle timers through theMicroTech keypad.The compressor should pump down the circuit until theevaporator pressure reaches 2 psig (14 kPa) or 60 sec-onds has elapsed, whichever occurs first.Upon completing the full pumpdown per step 5, the“FullPumpDwn” setpoint is automatically changed back to“No”which reverts backtostandard 34 psig (235 kPa) stoppumpdown pressure.If the pumpdown does not go to 2 psig (14 kPa) on the firstattempt, one more attempt can be made by repeatingsteps 3,4 and 5 above. Do not repeat “FullPumpDwn”more than once to avoid excessive screw temperaturerise under this abnormal condition. A no liquid startalarm and shutdown may occur during this proce-dure. Proceed as noted in step number 8.The circuit is now in the deepest pumpdown which cansafely be achieved by the use of the compressor. Anyremaining refrigerant must be removed from the circuit bythe use of a refrigerant recovery unit.

Remove and replace the filter-drier(s). If the refrigerantcircuit is opened for more than 10 minutes evacuate the linesthrough the liquid line manual shutoff valve(s) to removenoncondensables that may have entered during filter re-placement. A leak check is recommended before returningthe unit to operation.

Liquid line solenoid valveThe liquid line solenoid valves that shuts off refrigerant flowin the event of a power failure, do not normally require anymaintenance. (The electronic expansion valve, on a suddenpower failure, remains open to the position it was at when thepower failure occurred. During normal operation the EEVcloses for automatic pumpdown and the liquid line solenoidvalve closes only when the compressor stops.) They may,however, require replacement of the solenoid coil or of theentire valve assembly.

The solenoid coil can be checked to see that the stem ismagnetized when energized by touching a screwdriver to thetop of the stem. If there is no magnetization either the coil isbad or there is no power to the coil.

The solenoid coil may be removed from the valve bodywithout opening the refrigerant piping after first movingpumpdown switches PS1, PS2 and PS3 to the “manualpumpdown”position and opening the S1 switch. For personalsafety shut off and lock out the unit power.

The coil can then be removed from the valve body bysimply removing a nut or snap-ring located at the top of thecoil. The coil can then be slipped off its mounting stud forreplacement. Be sure to replace the coil on its mounting studbefore returning pumpdown switches PS1 , PS2 and PS3 tothe “auto pumpdown” position.

To replace the entire solenoid valve follow the stepsinvolved when changing a filter-drier.

Liquid injection solenoid valveLiquid injection is required during compressor operation toseal and cool the screw. A liquid injection sensor is installedon the compressor to assure that liquid injection occurswhenever the compressor is running. A failure of the liquidinjection solenoid valve to open will cause the compressor toshut down due to lack of liquid injection.

The liquid injection solenoid valve, like the liquid linesolenoid valve, only closes when the compressor stops.

Since this valve is open during pumpdown the refrigerant inthe line will cause the suction pressure to rise 10 to 20 psig (69to 138 kPa) after shutdown occurs. The solenoid coil andvalve body can be removed as in the same procedure as theliquid line solenoid valve but it is important that the S1 switchbe opened first.

Electronic expansion valveThe electronic expansion valve is located adjacent to thecompressor. The refrigerant is piped so it first passes throughthe electronic expansion valve, then through the motor hous-ing cooling the motor, before going into the evaporator. Referto the Refrigerant Piping Schematic found on page 35.

The expansion valve is responsible for allowing the properamount of refrigerant to enter the evaporator to match thecooling load. It does this by maintaining aconstantsuperheat.(Superheat is the difference between refrigerant temperatureof the vapor as it leaves the evaporator and the saturationtemperature corresponding to the evaporator pressure.) AllALS chillers are factory set for between 8°F (4.5”C) and 12°F(6.6”C) superheat at 75% to 100% load and between 6°F(3.3”C) and 10°F (5.6”C) below 75% load. The superheat iscontrolled by the microprocessor and is not adjustable.

The expansion valve, like the solenoid valve, should notnormally require maintenance, but if it requires replacement,the unit must be pumped down by following the steps involvedwhen changing a filter-drier.

If the problem can be traced to the electric motor only, itcan be unscrewed from the valve body without removing thevalve but only after pumping the unit down. Disassemblevalve at the brass hex nut. Do no disassemble valve at thealuminum housing.

Electronic expansion valve operationThere are 3 colored indicator LEDs (green, red, yellow)located in the control panel on the electronic expansion valve(EXV) board. When the control panel is first powered themicroprocessor will automatically step the valve to the fullyclosed (shut) position and the indicator lights on the EXV willblink in sequence. The valve can also be heard closing as itgoes through the steps. The valve will take approximately 14seconds to go from a full open position to a full closed position.

The position of the valve can be viewed at any time by usingthe MicroTech keypad through the circuit pressures menus.There are a total of 760 steps between closed and full open.

A feature of the electronic expansion valve is a maximumoperating pressure setting (MOP). This setting limits the loadon the compressor during start-up periods where high returnevaporator water temperatures may be present. The valvewill limit the maximum suction pressure at start-up to approxi-mately 85 psig (586 kPa). The valve will close to a pointnecessary to maintain the 85 psig (586 kPa). During this timethe superheat will rise above 12°F (6.6°C) and not drop below12°F (6.6°C) until the suction pressure drops below 85 psig(586 kPa). The valve will maintain evaporator pressure closeto 85 psig (586 kPa) until the evaporator water temperaturedecreases to approximately 55 to 60°F (12.7 to 15.6°C).

When the circuit starts the valve opens as soon as theevaporator pressure decreases to 40 psig (275 kPa). At theend of the cooling cycle the valve closes to cause the systemto pump down. The valve closes at the rate of approximately55 steps per second, or from full open to full closed inapproximately 14 seconds. The valve closing duringpumpdown will occur in approximately 20-30 seconds afterthe pumpdown switch is moved to the “Pumpdown and Stop”position.

IM 548 / Page 39

Figure 15. Electronic expansion valve Figure 16. Top view of typical dual circuitshei/ and tube evaporator

/Liquid Connections

- RaintIght FlexConnector

Bonnet

Extended Copper

Another method is to place a cork plug in each tube on bothends of the cooler and applying pressure to the shell of thecooler. After a period of time the pressure will leak from theshell into the leaking tube or tubes and pop out the cork plug.

Bottom

Refrigerant chargingALS air cooled screw chillers are shipped factory charged

operating charge found in the physical data tables on pages

with a full operating charge of refrigerant but there may be

12-13.

times that a unit must be recharged at the jobsite. Followthese recommendations when field charging. Refer to the unit

EvaporatorThe evaporator is of the direct expansion, shell-and-tube typewith refrigerant flowing through the tubes and water flowingthrough the shell over the tubes. The tubes are internallyfinned to provide extended surface as well as turbulent flowof refrigeration through the tubes. Normally no service workis required on the evaporator. There may be instances wherea tube will leak refrigerant into the water side of the system.In the cases where only one or two tubes leak, the problemcan best be solved by plugging the tube at both ends. Whenthe tube must be replaced, the old tube can be removed andreplaced. Follow the requirements set forth by the EPA forthe pumpdown and recovery of refrigerant.

To remove a tube, the unit should be temporarily pumpeddown. Follow the steps involved when changing a filter-drier.These steps will insure a minimum amount of refrigerant losswhen the evaporator is opened up. The tubes are mechani-cally expanded into the tube sheets at each end of theevaporator. In order to remove the tubes, it is necessary tobreak this bond by collapsing the tube. After doing this at bothends of the shell, the tube can be removed for replacement.The new tube can then be inserted and re-expanded into thetube sheet.

Note: The bond produced by expansion must be refriger-ant tight. This bond must be produced by applying Locktite(red) to the tube and rolling it into the tube sheet.

After reassembling the evaporator, a small amount ofrefrigerant should be introduced by momentarily opening themanual liquid line valve. A leak check should then be per-formed on the evaporator.

Tube removal can only take place after the leaking tube islocated. One method that would work would be to subjecteach tube to air pressure by plugging each end and, with apressure gauge attached to one of the end plugs, observingif there is a loss of air pressure over a period of a minute ortwo.

ALS air cooled screw chillers are more sensitive to under-charging than to overcharging therefore it is preferable to beslightly overcharged rather than undercharged on a circuit.The optimum charge is the charge which allows the unit to runwith a solid stream of liquid in the liquid line at all operatingconditions. When the liquid line temperature does not dropwith the addition of 5-10 Ibs of charge then the subcooler isnearly full and proper charge has been reached. If the liquidline temperature does not drop and the discharge pressuregoes up 3-5 psig (20.7-34.5 kPa)as 5-10 Ibs of refrigerant is-added the correct maximum charge has been reached.

Unit charging can be done at any steady load condition, atany outdoor ambient temperature. Unit must be allowed torun 5 minutes or longer so that the condenser fan staging isstabilized at normal operating discharge pressure. For bestresults charge with 2 or more condenser fans operating perrefrigerant circuit.

The ALS units have a condenser coil design with approxi-mately 15% of the coil tubes located in a subcooler section ofthe coil to obtain liquid cooling to within 5°F (3°C) of theoutdoor air temperature when all condenser fans are operat-ing. This is equal to about 15-20°F (8.3-l 1 .l’C) subcoolingbelow saturated condensing temperature when pressure isread at the liquid valve between the condenser coil and theliquid line filter drier. Once the subcooler is filled extra chargewill not lower the liquid temperature and does not help systemcapacity or efficiency. However, a little extra (1 O-l 5 Ibs) willmake the system less sensitive.

Note: As the unit changes load or fans cycle on or off, thesubcooling will vary but should recover within several minutesand should never show below 6°F (3.3”C) subcooling at anysteady state run condition. Subcooling will vary somewhatwith evaporator leaving water temperature and suction su-perheat. As the evaporator superheat goes lower thesubcooling will drop slightly.

Page 40 / IM 548

Excessive refrigerant losses can also leak oil from thesystem. When adding charge, if there is visible evidence of asignificant oil leakage, add an additional oil charge equivalentto 0.04 pints x the Ibs. of refrigerant charge required. (Ex-ample: for every 10 Ibs. of refrigerant charge add .4 pints ofoil.)

A leak in the unit could be very small and have little effecton system operation or could be severe enough to cause theunit to shut down on a safety trip.

One of the following three scenarios will be experiencedwith an undercharged unit.1. If the unit is slightly undercharged the unit will show

bubbles in the sightglass. Recharge the unit as describedin the charging procedure below.

2. If the unit is moderately undercharged the unit will mostlikely trip on freeze protection. Recharge the unit asdescribed in the charging procedure below.

3. If the unit is severely undercharged the unit will trip off dueto lack of liquid injection. In this case either remove theremaining charge by means of a proper reclamation sys-tem and recharge the unit with the proper amount ofrefrigerant as is stamped on the unit nameplate, or addrefrigerant through the suction valve on the compressor.Feed liquid into the suction valve when the compressor isrunning. If the unit is severely undercharged the unit maynuisance trip during this charging procedure. If this hap-pens close off the refrigerant from the tank and restart theunit. Once the unit has enough charge so that it does nottrip out continue with step 2 of the charging procedurebelow.

Procedure to charge a moderately undercharged ALSunit:1. If a unit is low on refrigerant you must first determine the

cause before attempting to recharge the unit. Locate andrepair any refrigerant leak. Evidence of oil is a goodindicator of leakage however, oil may not be visible at allleaks. Liquid leakdetectorfluids work well to show bubblesat medium size leaks but electronic leak detectors may beneeded to locate small leaks.

2. Add the charge to the system through the suction shutoffvalve or through the schrader fitting on the tube enteringthe evaporator between the compressor and the evapora-tor head.

3. The charge can be added at any load condition between25100% load per circuit but at least 2 fans should beoperating per refrigerant circuit if possible. The suctionsuperheat should be in the 6”-12°F (3.3-6.6”(Z) range.

4. Add sufficient charge to clear the liquid line sight glass anduntil all flashing stops in the sightglass. Add an extra 15-20 Ibs. of reserve to fill the subcooler if the compressor isoperating at 50-100% load.

5. Check the unit subcooling value on the MicroTech displayor by reading the liquid line pressure and temperature atthe liquid line near the filter-drier. The subcooling valuesshould be between 6”-20°F (6.6-l 1 .l”C). The subcoolingvalues will be highest at 75-100% load, approximately12”--20°F (6.6-11 .1°C) and lowest at 50% load, approxi-mately 6”-;2”F (3.3-6.6”C).

6. With outdoor temperatures above 60°F (15.6”C) all con-denser fans should be operating and the liquid line tem-perature should be within 5”-10°F (2.8-5.6”C) of outdoorair temperature. At 25-50% load the liquid line tempera-ture should be within 5°F (2.8”C) of outdoor air tempera-ture with all fans on. At 75-100% load the liquid linetemperature should be within 10°F (5.6”C) of outdoor airtemperature with all fans on.

7. Overcharging of refrigerant will raise the compressor dis-charge pressure due to filling of the condenser tubes withexcess refrigerant after the liquid line temperature hasreached its minimum value.

IM 546 / Page 41

In-Warranty Return Material Procedure

CompressorThe McQuay International warranty provides for repair orreplacement, at the Company’s option, of components sup-plied by it that may fail within the warranty period. Screw typecompressors fall into this category.

In the event of a failure contact the nearest McQuayServiceoffice for assistance. During the first year’s installation period,warranty labor and parts will be furnished by McQuayServiceat no charge (excludes export) if the failure is determined tobe a defect in material or workmanship within McQuay Inter-national control.

ALS units purchased with a four year extended compres-sor warranty may or may not include extended period war-ranty labor depending upon the initial purchase agreement. Ineither event McQuayService should be contacted to handlethe repair or replacement of the compressor.

Components other than compressorsMaterial may not be returned except by permission ofauthorized factory service personnel of McQuay Interna-tional at Minneapolis, Minnesota. A “return goods” tag will besent to be included with the returned material. Enter theinformation as called for on the tag in order to expeditehandling at our factories and prompt issuance of credits.

The return of the part does not constitute an order forreplacement. Therefore, a purchase order must be enteredthrough your nearest McQuay representative. The ordershould include part name, part number, model number andserial number of the unit involved.

Following our personal inspection of the returned part, andif it is determined that the failure is due to faulty material orworkmanship, and in warranty, credit will be issued oncustomer’s purchase order.

All pans shall be returned to the pre-designated McQuayfactory transportation charges prepaid.

Page 42 / IM 548

Appendix

Standard controlsThermistor SensorsNote: Refer to IM 549 for a more complete description of thecontrols application, settings, adjustments, and checkoutprocedures.

All sensors are premounted and connected to theMicroTech field wiring strip with shielded cable. A descriptionof each sensor is listed here. For location of each sensor referto Figure 17.

Evaporatorleaving water temperature -This sensor islocated on the evaporator water outlet connection and is usedfor capacity control of the chiller and low water temperaturefreeze protection.

Evaporator entering water temperature-This sensoris located on the evaporator water inlet connection and isused for monitoring purposes and return water temperaturecontrol.

Evaporator pressure transducer circuit # 1 - Thissensor is located on the suction side of compressor # 1 andis used to determine saturated suction refrigerant pressureand temperature. It also provides low pressure freeze protec-tion for circuit # 1.

Evaporator pressure transducer circuit # 2 - Thissensor is located on the suction side of compressor # 2 andis used to determine saturated suction refrigerant pressureand temperature. It also provides low pressure freeze protec-tion for circuit # 2.

Table 25. Sensor location chart

Evaporator pressure transducer circuit # 3 - Thissensor is located on the suction side of compressor # 3 andis used to determine saturated suction refrigerant pressureand temperature. It also provides low pressure freeze protec-tion for circuit # 3.

Condenser pressure transducer circuit # 7 - Thesensor is located on the discharge of compressor # 1 and isused to readsaturated refrigerant pressure and temperature.The transducer will unload the compressor should a rise inhead pressure occur which is outside the MicroTech setpointlimits. The signal is also used in the calculation of circuit #1subcooling.

Condenser pressure transducer circuit # 2 - Thesensor is located on the discharge of compressor # 2 and isused to read saturated refrigerant pressure and temperature.The transducer will unload the compressor should a rise inhead pressure occur which is outside the MicroTech setpointlimits. The signal is also used in the calculation of circuit #2subcooling.

Condenser pressure transducer circuit # 3 - Thesensor is located on the discharge of compressor # 3 and isused to read saturated refrigerant pressure and temperature.The transducer will unload the compressor should a rise inhead pressure occur which is outside the MicroTech setpointlimits. The signal is also used in the calculation of circuit #3subcooling.

Figure 17. Sensor Locations

IM 548 I Page 43

Outside air - This sensor is located on the back of thecontrol box on compressor # 1 side. It measures the outsideairtemperature, is used to determine if low ambient start logicis necessary and can be the reference for low ambienttemperature lockout.

Suction temperature circuit # 1 -The sensor is locatedin a well brazed to circuit # 1 suction line. The purpose of thesensor is to measure refrigerant temperature to control andmaintain proper superheat.

Suction temperature circuit#2-The sensor is locatedin a well brazed to circuit # 2 suction line. The purpose of thesensor is to measure refrigerant temperature to control andmaintain proper superheat.

Suction temperature circuit # 3-The sensor is locatedin a well brazed to circuit # 3 suction line. The purpose of thesensor is to measure refrigerant temperature to control andmaintain proper superheat.

Liquid line temperature circuit # 1 - The sensor islocated in a well brazed to circuit # 1 liquid line. It measuresthe refrigerant temperature and is used to calculate subcooling.

Liquid line temperature circuit # 2 - The sensor islocated in a well brazed to circuit # 2 liquid line. It measuresthe refrigeranttemperatureandisusedtocalculatesubcooling.

Liquid line temperature circuit # 3 - The sensor islocated in a well brazed to circuit # 3 liquid line. It measuresthe refrigeranttemperature and is used tocalculate subcooling.

Demand limit -This requires a field connection of a 4 -20 milliamp DC signal from a building automation system. Itwill determine the maximum number of cooling stages whichmay be energized.

Evaporator water temperature reset - This requires a4-20 milliamp DC signal from a building automation system ortemperature transmitter to reset the leaving chilled watersetpoint.

Percent total unit amps - (Optional) This is located inthe power side of the control panel. An adjustable voltageresistor and a signal converter board sends a DC signalproportional to the total compressor motor current to themicroprocessor.

Liquid presence sensorEach compressor is equipped with a liquid sensor to assurethat liquid flows to the compressor for cooling and sealingduring operation. The sensor will shutdown the compressor inthe event no liquid is sensed. At start-up the liquid sensorchecks for excessive liquid in the compressor and will delaystart until the compressor heater transfers the liquid out of thecompressor and into the condenser. A liquid trip by the sensorwill produce an alarm message on the MicroTech display.

High condenser pressure controlMicroTech is also supplied with high pressure transducers oneach refrigerantcircuit. Although the main purpose of the highpressure transducer is to maintain proper head pressurecontrol, another purpose is to convey a signal to the MicroTechcontrol to unload the compressor in the event of an excessiverise in discharge pressure to within 20 psi (138 kPa) below thecondenser pressure control setpoint of 380 psig (2620 kPa).The MicroTech control is set to not allow additional circuitloading approximately 30 psi (207 kPa) below the high pres-sure switch trip setting. The high pressure alarm is in re-sponse to the signal sent by the pressure transducer. Thehigh pressure transducer can be checked by elevating dis-charge pressure (see Mechanical High Pressure Safety Con-trol) and observing the MicroTech display (or a pressuregage), and unit operation as the pressures pass the risinghigh pressure values noted. After the test reset the HighCondenser Pressure alarm setpoint to 380 psig (2620 kPa).

Mechanical high pressure safety controlThe high pressure safety control is a single pole pressureactivated switch that opens on a pressure rise. When theswitch opens, the control circuit is de-energized droppingpower to the compressor and fan motor contactors. Theswitch is factory made to open at 400 psig (2760 kPa)(*lOpsig) and reclose at 300 psig (2070 kPa). Although the highpressure switch will close again at 300 psig (2070 kPa), thecontrol circuit will remain locked out and it must be resetthrough MicroTech.

The control is mounted on the compressor attached to afitting ahead of the discharge shut off valve.

To check the control first manually load circuit #1 to 75%load. Adjust the High Condenser Pressure control to 415 psig(2862 kPa) through the “Alarm Spts” menu of the keypad.Remove wire 133 from terminal 20 of the MicroTech controller.This will disable all but one fan. Observe the cut out point of thecontrol through the MicroTech keypad display, or by means ofa service gauge on the back seat port on the discharge servicevalve. Important: Closely monitor the High Pressure Con-trol and stay within reach of the emergency stop switch.Do not let the pressure exceed 420 psig (2900 kPa) duringthe test. If the condenser pressure reaches 420 psig (2900kPa) open the emergency stop switch. The MicroTechkeypad display may read slightly lower than a service gauge.Upon completion of the test reset the High PressureControl back to 380 psig (2620 kPa).

To check the control on circuit #2 repeat the same proce-dure after removing wire 233 from terminal 30.

Compressor motor protectionThe compressors are supplied with two types of motor protec-tion. Solid state electronic overloads mounted in the controlbox sense motor current within 2% of accuracy of the operat-ing amps. The must trip amps are equal to 140% of unitnameplate compressor RLA. The must hold amps are equalto 125% of unit nameplate RLA. A trip of these overloads canresult from the unit operating outside of normal conditions.Repeat overload trips under normal operation may indicatewiring or compressor motor problems. The overloads aremanual reset and must be reset at the overload as well asthrough MicroTech.

The compressors also have a solid state guardister circuitwhich provides motor over temperature protection. The‘guardister circuit has automatic reset but must also be resetthrough MicroTech.

FanTrol head pressure controlFanTrol is a method of head pressure control which automati-cally cycles the condenser fans in response to condenserpressure. This maintains head pressure and allows the unit torun at all ambient air temperatures.

All ALS units have independent circuits with the fans beingcontrolled independently by the condensing pressure of eachcircuit. If one circuit is off all fans on that circuit will also be off.The use of multiple fans enables the unit to have excellenthead pressure control at low outside ambients by cycling tomaintain the compressor discharge pressure within the de-sired operating band.

At outdoor ambient temperatures above approximately65°F (18.3”C) all of the fans for a circuit will be operating toachieve the most efficient unit operation. At any compressorload condition of 50% or above the unit has the highest overallefficiency with all fans operating. When the compressor un-loads below 50% the last fan stage is cut off because the fanenergy saved is more than the compressor power increase atthis light loading. Below approximately 65°F (18.3X) outdoortemperature the fans are cycled off as needed on eachrefrigerant circuit by the MicroTech control to maintain thecompressor discharge pressure in the optimum range for bestunit operation and highest overall efficiency.

Page 44 / IM 548

Fans are controlled by MicroTech in response to thesystem discharge pressure. The use of MicroTech to stageon the fans as needed allows more precise control andprevents undesirable cycling of fans.

One fan always operates with the compressor and otherfans are activated one at a time as needed. The control uses6 stages of fan control, with 4 outputs to activate up to 6additional fans per circuit. MicroTech logic sequences fancontactors to stage one fan at a time. On units with 6 or 7 fansper circuit a single fan is cut off when 2 fans are started toachieve adding one operating fan. See Tables 26 and 27.

Table 26. Fan staging and number of fans operating

ALSWSA ttrtu ALS14OA (Fms per CktS)MicroTech Fan Stage’ 0 ~ 1Fan Outout On - 1

Note: On AL155A thru ALS170A thru 280A two fans arecontrolled by fan output #4.

On ALS175A thru 195A two fans each are contolled by fanoutputs #3 and #4.

Table 27. Fan staging and number of fans operating

ALSZOSA thru ALS420A Ckt 3 (Fan8 per Ckt-6)

Fan Output On 1,2,3 ) 1,2,4 1,2,3,4T&al Fans 1

1Operating 1 -1-m+ 2 ~1 314 1 -5 6

ALS235A thru 2SOA (Fims per Ckt = 6)

MicroTech Fan Stage! 0 1 2 3 14 5

Fan Output On 1- 1,2 1,2,3 ~ 1,2,4 1,2,3,4

Total Fans Operating 1 2 3 4 5 6

Note: On ALS205A thru-220A Ckt #3 only and ALS235A thru280A two fans are controlled by fan output #4.

Several factors are evaluated by the MicroTech controllerto determine the number of fans to be operated. Theseinclude:

What is the compressor loading as percent of full load?What is the minimum lift pressure required at this load?(The lift pressure equals the discharge pressure minus thesuction pressure.)A control pressure band is added to the minimum liftpressure to prevent fan cycling.A target discharge pressure is determined by adding theminimum lift pressure to the suction pressure.At any operating condition the MicroTech controller will

determine the minimum lift pressure and a target dischargepressure, and will add or remove operating fans in sequenceuntil the discharge pressure reaches the target value or fallswithin the control band of pressure set just above the targetpressure value.

Each fan added has a decreasing percentage effect so thecontrol pressure band is smaller when more fans are on andlargest with only 1 or 2 fans on.

Unit operation, with FanTrol, is satisfactory down to out-door temperatures of 30°F (-1 .l”C). Below this temperaturethe SpeedTrol option is required to regulate the speed of thefirst fan on the system to adequately control the dischargepressure. With the SpeedTrol option unit operation down to0°F (-17.8”C) outdoor temperature is permitted assumingthat no greater than a 5 mph wind is present.

For windy locations operating below 30°F (-1.1 “C) out-door air temperature, wind gusts must be prevented fromblowing into the unit coils by either locating the unit in aprotected area, by the addition of field supplied wind barriers,mounting the optional wind baffles on the unit or any combi-nation of the above.

FanTrol operation example:Unit operating at 100% load on both circuitsSuction Pressure = 65 psig (448 kPa)Minimum lift pressure at 100% load = 120 psig (828 kPa)Minimum discharge pressure =

65 + 120 psig = 185 psig (1276 kPa)Discharge pressure control band = 35 psig (241 kPa)Maximum discharge pressure =

185+35=220psig(1517kPa)

If the discharge pressure is between the minimum of 185psig (1276 kPa) and maximum of 220 psig (1517 kPa) the fanstages in operation are correct and if the pressure fallsoutside this range the MicroTech controller will stage fans onor off to bring it within range.

SpeedTrol and FanTrol will provide reasonable oper-ating refrigerant discharge pressures to the ambienttemperatures listed for them provided the coil is notaffected by the existence of wind. If wind may occurit is the responsibility of the system designer orinstaller to make other provisions for low ambientcontrol. Consideration should be given to factorysupplied wind baffles as required to satisfy specificjob conditions.

Low ambient startLow ambient start is incorporated into the MicroTech logic.The MicroTech will measure the difference betweenfreezestatand evaporator pressure and determine the length of time thecompressor will be allowed to run (to build up evaporatorpressure) before taking the compressor off line. The dangerof allowing the compressor to run for to long before buildingup evaporator pressure is that the evaporator could freeze.The low ambient timer is determined by the pressure differ-ence between freezestat and evaporator pressure as shownin table If the low ambient timer is greater than the maximumtime allowed the MicroTech will shut off the compressor anddisplay an alarm.

Table 28. Pressure difference vs. time to alarm

0 psig (0 kPa) I 360 I

IM 548 / Page 45

Phase/voltage monitorThe phase/voltage monitor is a device which provides protec-tion against three-phase electrical motor loss due to powerfailure conditions, phase loss, and phase reversal. Wheneverany of these conditions occur, a contact opens to the MicroTech‘controller (PVR Input) which then de-energizes all inputs.

When proper power is restored, contacts close andMicroTech enables compressors for operation.

When three-phase power has been applied, the outputrelay should close and the “run light” should come on. If theoutput relay does not close, perform the following tests.

Check the voltages between L1-L2, L1 -L3 and L2-L3.These voltages should be approximately equal and within+10% of the rated three-phase line-to-line voltage.If these voltages are extremely low or widely unbalancedcheck the power system to determine the cause of theproblem.If the voltages are good, using a phase tester, verify thatphases are in A,B,C sequence for L1, L2 and L3. Correctrotation is required for compressor operation. If required todo so by phase sequence, turn off the power and inter-change any two of the supply power leads at the discon-nect.This may be necessary as the phase/voltage monitor is

sensitive to phase reversal. Turn on the power. The outputrelay should now close after the appropriate delay.

Compressor short cycling protectionMicroTech contains logic to prevent rapid compressor start-ing. Excessive compressor starts can be hard on startingcomponents and create excessive motor winding tempera-tures. The anti-cycle timers are set for a 5 minute stop-to-startand a 15 minute start-to-start. Both are adjustable throughMicroTech and can be manually overridden by the servicetechnician.

Optional controlsSpeedTrol head pressure control (optional)The SpeedTrol system of head pressure control operates inconjunction with MicroTech’s standard head pressure controlby modulating the motor speed on fans 11, 21 and 31 inresponse to condensing temperature. By reducing the speedof the last fan as the condensing pressure falls, the unit canoperate at lower ambient temperatures. Start-up in low ambi-ent is improved because the SpeedTrol fans 11,21 and 31 donot start until the condenser pressure builds up.

The SpeedTrol fan motor is a single phase, 208-230/460volt, thermally protected motor specially designed forvariablespeed application. The solid-state speed controls SC1 1,SC21 and SC31 are mounted above the control box outsideof condenser fans 11, 21 and 31 fan compartment, and areaccessible through the panel directly above the control box.Units with 460 volt power have a transformer mounted insidethe condenser fan compartment to step the voltage down to230 volts for the SpeedTrol motor.

The SpeedTrol control starts to modulate the motor speedat approximately 230 psig (1586 kPa) and maintains a mini-mum condensing pressure of 170 to 180 psig (1172 to 1241kPa). The motor speed is maximum at 230 psig (1586 kPa)and minimum at 170 psig (1172 kPa).

Reduced inrush start (optional)Reduced-inrush start is available on all voitage units andconsists of a 2 contactor arrangement with a solid state timedelay wired in series with the second contactor that energizesthe second winding of each compressor motor. Its purpose isto limit current inrush to the compressors upon start-up. Aseach compressor starts, the power to the coil of the secondcontactor is delayed for 1 second. With the first compressorcontactor energized the windings are connected in series to

draw reduced amperage. With the second contactor ener-gized the windings are connected in parallel.

Control checkout is best accomplished by observation aseach contactor is pulled in to see that the 1 second delayoccurs before the second contactor pulls in.

Hot gas bypass (optional)Hot gas bypass is a system for maintaining evaporatorpressure at or above a minimum value that allows continousoperation of the chiller at light load conditions. The purposeof doing this is to keep the velocity of the refrigerant as itpasses through the evaporator high enough for proper oilreturn to the compressor when cooling load conditions arelight.

The system consists of a pressure regulating valve with anintegral solenoid as shown below. The solenoid valve isfactory wired to open whenever the unit thermostat calls forthe first stage of cooling. The pressure regulating valve isfactory set to begin opening at 58 psig (400 kPa). For lowtemperature operation the valve must be reset. This settingcan be changed with an adjustment nut. To raise the pressuresetting, turn the adjustment screw clockwise. To lower thesetting, turn the screw counterclockwise. Do not force theadjustment beyond the range it is designed for, as this willdamage the adjustment assembly.

With the unit operating at 50% or lower circuit load theregulating valve opening can be determined. The regulatingvalve opening point can be determined by slowly reducing thesystem load orthrottling the ball valve on the liquid line at theentrance to the evaporator. Observe the suction pressurewith refrigerant gauges when the hot gas bypass valve cutsin. A slower but alternate method would be to lower the outletwater temperature to a value where the hot gas bypass valvestarts to open. When the bypass valve starts to open, therefrigerant line on the evaporator side of the valve will beginto feel warm to the touch.

Figure 18. Hot gas bypass piping diagram

4.62 max

11.00 (l%ODF)11.06 (1% ODF)

Wind baffles and hail guards (optional)Wind baffles can be supplied as a field installed option toreduce the negative effects on head pressure from windblowing over the vertical condenser coils. Wind baffles willpermit stable operation at reduced ambient temperatures andshould be considered on all low ambient jobs or anytime thatwind may be a factor.

Page 46 / IM 548

ALS controls, settings and functions

Table 31.

Description

Compressor Hestera

Compreesar

Solenoid - Tap

Compressor

Solenald - Bottom

Comprersor

Function

To provide heat to drive off liquid refrigerant

when compssor is off.

In clrcult 1, 2 and 3 energizes to load 50% of

compressor capacity.

In clrcult 1, 2 and 3 energizes to unload 259’, of

compressor c?Elty.

In clrcult 1, 2 and 3 energizes to load 25% of

or to prevent freezing

Symbol Setting Reset Location

HTRl,2,3 On, when N/A On the Compressor

compressor is off.

CS’1.21, N/A N/A On the Compressor

31

cs12.22. N/A N/A On the Compressor

32

CS’3.23. N/A N/A On the Compressor

On the Cooler

Control Box

ient unit refrigerant flow and

provide motor temperature protectlon at about 220”

tect compressor from starting with llquld or

etc.. safety code to prevent h!gh

It and all safetles. Refer to IM 549.

To protect the compressor motor from over heating

In Controller Code N/A

Inherent in desw

Refer to IM 549 Refer

Manual

On the Compressor

main liquid line

Control Box

On the Compressor

Control Box

Control Box

Control Box

Control Box

Control box

set delay for reduced Inrush.

To convert AC current sIgnal volts to DC volts

w the unit to run with very low load.

o provide a positive shut off of liquid refrigerant

liquid injectlon when the

ore uniform head pressure control.

rom high voltage spikes and surges.

TDf>,6.7 N/A

SV!,2,7 N/A

N/A Control Box

Control Box

Discharge Line

Liquid Line

On Compressor

Liquid Inlection

Above Control Box

Control Box

Power Side

IM 548 I Page 49

ALS troubleshooting chart

Table 32.

2. Check unit status on MicroTech display. Close switch

PS3 rn pumpdown posrtron. 3. Check clrcurt status on MicroTech display. Close swatch.

4. Check unit status on MIcroTech dtsplay. Close switch.

5. Close circuit breakers.

own or crrcur 6 Check electrrcal circuits and motor windings for shorts or grounds.

Investrgate for possible overloading.

Check for loose or corroded connections.

7. Unit phase voltage monitor not satisfied.

8. Compressor overload tripped.

Reset breakers or replace fuses after fault is corrected

7 Check unit power wiring to unit for correct phasing Check voltage.

8. Overloads are manual reset. Reset overload at button on overload.

Clear alarm on MIcroTech.

9. Defective compressor contactor or contactor co11

10. System shut down by safety devices.

11. No cooling requrred.

12. Motor electrical trouble.

13. Loose wiring.

9 Check wrrrng Repair or replace contactor.

IO. Determrne tyfle and cause of shutdown and correct problem

before attempting to restart.

11. Check control settings. Wart unttl unit calls for cooling.

12. See 6, 7, 8 above.

13. Check crrcurts for voltage at required points

Tighten all power wiring terminals.

1. Check supply voltage for excessive voltage drop.

2. Check and trghten all connections

3. Check supply voltage.

efectrve capacity control solenoids.

2. Unloader mechanism defective.

1 Check solennrds for proper operation. See capacity control section.

clogged filter drier or low charge.

3. Inadequate liquid to liquid injectron during run.

2. Check lrqurd injection line sight glass.

If flashing check filter drier and unrt charge.

3. Check lrqurd Injectron line sightglass.

If flashrng check filter-drier and unit charge.

Discharge pressure too low. Protect condenser coil from wind.

PV&SSUre

2. Noncondensahles in the system.

3. Fans not running.

4. Fan control out of adjustment

5. System overcharged with refrrgerant.

6. Dirty condenser coil.

7. Arr recirculation from outlet into unit coils

8. Air restriction into unit

1. Wind effect at low amhients. _

2. Condenser fan control not correct

3. Low suction pressure.

3. Check fan fuses and electrrcal circuits.

4. Check that unrt setup in MicroTech matches the unit model number.

Check MicroTech condenser pressure sensor for proper operation.

5. Check for excessive suhcoolrng above 30°F (-1 .I “C).

Remove the excess charge.

6. Clean the condenser coil

7. Remove the cause of recrrculation.

8. Remove obstructions near unit _..~_~ 1 Protect unrt agarnst excessive wind into vertical ~011s.

2. Check that unit setup in MIcroTech matches the unit model number.

Check SpeetlTrol fan on units with SpeedTrol optron.

3 See Correctrve Steps for low suction pressure.

4. See Corrective Steps for failure to load.

ection at start.

4. Insufficient water flow to evaporator.

5. Water temperature leaving evaporator is too low.

6. Evaporator tubes fouled.

7, Evaporator head ring gasket slrppage.

cessive load - high water temperature.

2. Check pressure drop across filter-drier. Replace cores.

3. Check expansron valve superheat and valve Opening position.

Replace valve only if certain valve is not working.

4. Check water pressure drop across the evaporator and Adfust gpm.

5. Adjust water temperature to higher value.

6 Inspect by removing water piping. Clean chemically.

7. LOW suction pressure and low superheat both present may indicate

an Internal problem. Consult factory.

2. Compressor unloaders not loading compressor.

3. Superheat is too low.

2. See Correctrve Steps below for failure of compressor to load

3. Check superheat on MIcroTech display.

Check suction lrne sensor installation and sensor.

Page 50 I IM 548

Product Warranty

McQuay International, hereinafter referred to as the “Com-pany,” warrants that it will provide, at the Company’s option,either free replacement parts or free repair of componentparts in the event any product manufactured by the Companyand used in the United States proves defective in material orworkmanship within twelve (12) months from initial start-up oreighteen (18) months from the date shipped by the Company,whichever comes first. For additional consideration, the Com-pany warrants that for four (4) years following the initialwarranty period it will provide, at the Company’s option, freereplacement partsforthe motor-compressor, or, free replace-ment for any integral component of the motor-compressorwhich proves defective in material or workmanship.

To obtain assistance under this parts warranty, extendedmotor-compressor warranty, or extended heat exchangerwarranty, simply contact the selling agency. To obtain infor-mation or to gain factory help contact McQuay International,Warranty Claims Department, P.O. Box 1551, Minneapolis,MN 55440, telephone (612) 5535330.

Note: This warranty constitutes the buyer’s sole remedy.It is given in lieu of all other warranties. There is no impliedwarranty of merchantability or fitness for a particular purpose.In no event and under no circumstance shall the Company beliable for incidental or consequential damages, whether the

theory be breach of this or any other warranty, negligence ofstrict tort.

This parts warranty and the optional extended warrantiesextend only to the original user. Of course, abuse, misuse, oralteration of the product in any manner voids the Company’swarranty obligation. Neither the parts or extended warrantyobligates the Company to pay any labor or service costs forremoving or replacing parts, or any shipping charges. Refrig-erants, fluids, oils, and expendable items such as filters arenot covered by this warranty.

Attached to this warranty is a requirement for equipmentcontaining motor-compressors to report start-up information.The registration form accompanying the product must becompleted and returned to McQuay International within ten(10) days of original equipment start-up. If that is not done, thedate of shipment shall be presumed to be the date of start-upand the warranty shall expire twelve (12) months from thatdate.

No person (including any agent, salesman, dealer ordistributor) has authority to expand the Company’s obligationbeyond the terms of this express warranty, or to state that theperformance of the product is other than than that publishedby the Company.

m 13600 Industrial Park Blvd., P.O. Box 1551, Minneapolis, MN 55440 USA (612) 553-5330

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