Sequence of Operation...................................................................................................................41
2IM 676
Page 3
Introduction
General Description
McQuay SeasonPak air-cooled water chillers are complete, self-contained automatic refrigerating
units. Every unit is completely assembled, factory wired, charged, and tested. Each unit consists of
twin air-cooled condensers with integral subcooler sections, multiple accessible hermetic
compressors, replaceable tube dual circuit shell-and-tube evaporator, and complete refrigerant
piping. Liquid line components include manual liquid line shutoff valves, sight-glass/moisture
indicators, solenoid valves, and double diaphragm hydraulic element thermal expansion valves.
Other features include compressor crankcase heaters, an evaporator heater for chilled water freeze
protection, limited pumpdown during “on” or “off” periods, compressor lead-lag switch to alternate
the compressor starting sequence, and sequenced starting of compressors.
automatic operation. Condenser fan motors are fused in all three phases and started by their own
three-pole contactors. Compressors are not fused but may be protected by optional circuit breakers,
or by a field installed fused disconnect.
Inspection
Check all items carefully against the bill of lading. Inspect all units for damage upon arrival.
Report shipping damage and file a claim with the carrier. Check the unit name plate before
unloading, making certain it agrees with the power supply available. McQuay is not responsible for
physical damage after unit leaves the factory.
The electrical control center includes all safety and operating controls necessary for dependable
Note: Unit shipping and operating weights are available in the Physical Data tables
beginning on page 12.
Installation
Note: Installation is to be performed by qualified personnel who are familiar with local
codes and regulations.
WARNING
Sharp edges and coil surfaces are a potential hazard. Avoid contact with them.
Handling
Be careful to avoid rough handling of the unit. Do not push or pull the unit from anything other
than the base. Block the pushing vehicle away from the unit to prevent damage to the sheet metal
cabinet and end frame (see Figure 1).
To lift the unit, 2 1/2" (64mm) diameter lifting holes are provided in the base of the unit.
Arrange spreader bars and cables to prevent damage to the condenser coils or cabinet (see Figure 2).
IM 6763
Page 4
Figure 1, Suggested pushing arrangement
control box location)
Figure 2, Suggested lifting arrangement
Spreader bars
recommended (Use
Caution)
Blocking required
across full width
NOTE: Number of fans can vary
from this diagram. Lifting method
remains the same.
Must use these rigging
holes. (Be aware of
Location
Unit Placement
ALR units are for outdoor applications and can be mounted on a roof or ground level. Set units on a
solid and level foundation. For roof mounted applications, install the unit on a steel channel or Ibeam frame to support the unit above the roof. For ground level applications, install the unit on a
substantial base that will not settle. A one piece concrete slab with footings extended below the frost
line is recommended. Be sure the foundation is level (within 1/2” [13 mm] over its length and
width). The foundation must support the operating weights listed in the Physical Data tables
beginning on page 12.
On ground level applications protect fins against vandalism using the optional coil guards or by
erecting a screen fence. The fence must allow free flow of air to the condenser coil for proper unit
operation.
4IM 676
Page 5
Clearances
air inlet
The flow of air to and from the condenser coil must not be limited. Restricting air flow or allowing
air recirculation will result in a decrease in unit performance and efficiency. There must be no
obstruction above the unit that would deflect discharge air downward where it could be recirculated
back to the inlet of the condenser coil. The condenser fans are propeller type and will not operate
with ductwork on the fan outlet.
Install the unit with enough side clearance for air entrance to the coil and for servicing.
Provide service access to the evaporator, compressors, electrical control panel and piping
components as shown in Figure 3.
Do not allow debris to accumulate near the unit. Air movement may draw debris into the
condenser coil causing air starvation. Give special consideration to low ambient operation where
snow can accumulate. Keep condenser coils and fan discharge free of snow or other obstructions to
permit adequate airflow.
Figure 3, Clearance requirements
5 ft. (1524mm) Clearance for
air inlet
4 Ft.
(1220mm)
clearance for
5 Ft. (1524mm) clearance for
ALR Unit SizeMinimum "X" Dimension
032E -075E8 ft (2438 mm)
080E - 185E10 ft (3048 mm)
"X" clearance
for evaporator
tube removal
Sound Isolation
The ultra-low sound levels of the ALR reciprocating
chiller is suitable for most applications. When
additional sound reduction is necessary, locate the
unit away from sound sensitive areas. Avoid
locations beneath windows or between structures
where normal operating sounds may be
objectionable. Reduce structurally transmitted sound
by isolating water lines, electrical conduit and the
unit itself. Use wall sleeves and rubber isolated
piping hangers to reduce transmission of water or
pump noise into occupied spaces. Use flexible
electrical conduit to isolate sound through electrical
conduit. Spring isolators are effective in reducing the low amplitude sound generated by
reciprocating compressors and for unit isolation in sound sensitive areas.
Service Access
Each end of the unit must be accessible after installation for periodic service. Compressors, filterdriers, and manual liquid line shutoff valves are accessible on each side of the unit adjacent to the
control box. High pressure, low pressure, and motor protector controls are on the compressor.
Freezestats and cooler barrel thermostats are near the cooler. Most other operational, safety and
starting controls are located in the unit control box.
The condenser fan and motors can be removed from the top of the unit.
IM 6765
Page 6
Vibration Isolators
Vibration isolators are recommended for all roof mounted installations or wherever vibration
transmission is a consideration.
Table 1 lists isolator loads and type. Table 2 lists spring isolator part numbers for all unit sizes. See
Dimensional Data beginning on page 36 for dimensions required to secure each isolator to the
mounting surface.
Table 1, Isolator loads and type
ALRISOLATOR LOADS AND TYPE FOR EACH MOUNTING LOCATION
Local authorities can supply the installer with the proper building and safety codes required for safe
and proper installation.
Install piping with minimum bends and changes in elevation to minimize pressure drop.
Consider the following when installing water piping:
1. Vibration eliminators to reduce vibration and noise transmission to the building.
2. Shutoff valves to isolate the unit from the piping system during unit servicing.
3. Manual or automatic air vent valves at the high points of the system. Install drains at the
lowest points in the system.
4. A means of maintaining adequate system water pressure (expansion tank or regulating valve).
5. Temperature and pressure indicators located at the unit to aid in unit servicing.
6. A strainer or other means of removing foreign matter from the water before it enters the pump.
Place the strainer far enough upstream to prevent cavitation at the pump inlet (consult pump
manufacturer for recommendations). The use of a strainer will prolong pump life and keep
system performance up.
7. Place a strainer in the water line just before the inlet of the evaporator. This will help prevent
foreign material from entering and decreasing the performance of the evaporator.
CAUTION
If separate disconnect is used for the 110V supply to the evaporator heating cable, mark
the disconnect clearly to ensure disconnect is not accidentally shut off during cold seasons.
8. The shell-and-tube evaporator has a thermostat and heating cable to prevent freeze-up down to -
20°F (-29°C). It is suggested that the heating cable be wired to a separate 110V supply circuit.
As shipped from the factory, the heating cable is wired to the control circuit. All water piping
to the unit must also be protected to prevent freezing.
9. If the unit is used as a replacement chiller on a previously existing piping system, flush the
system thoroughly before unit installation. Regular water analysis and chemical water
treatment on the evaporator is recommended immediately at equipment start-up.
10. The total water volume in the system should be sufficient to prevent frequent “on-off” cycling.
Turnover rate should not be less than 15 minutes for normal variable cooling loads. Turnover
rate for process cooling or a constant load,should not be less than 6 minutes.
11. When glycol is added to the water system for freeze protection, the refrigerant suction pressure
will be lower, cooling performance less, and water side pressure drop greater. If the percentage
of glycol is high, or if propylene is used instead of ethylene glycol, the added pressure drop and
loss of performance could be substantial. Reset the freezestat and low leaving water alarm
temperatures. The freezestat is factory set to default at 36°F (2.2°C). Reset the freezestat
setting to approximately 4 to 5 degress F (2.3 to 2.8 degress C) below the leaving chilled water
setpoint temperature. See the section titled “Glycol Solutions” for additional information
concerning glycol.
12. Perform a preliminary leak check before insulating the piping and filling the system.
13. Piping insulation should include a vapor barrier to prevent condensation and possible damage
to the building structure.
IM 6767
Page 8
Figure 4, Typical field evaporator water piping
Vent
Outlet
Valved
pressure
gauge
Vibration
Eliminator
Flow
Switch
Balancing
valve
Gate valve
Protect all field piping
against freezing
Drain
Vibration
Eliminator
Water
strainer
Gate valve
Flow Switch
Mount a water flow switch in either the entering or leaving water line to shut down the unit when
water flow is interrupted.
A flow switch is available from McQuay (part number 00175033-00). It is a “paddle” type
switch and adaptable to any pipe size from 3” (76mm) to 8” (203mm) nominal. Certain minimum
flow rates are required to close the switch and are listed in Table 3. Installation should be as shown
in Figure 5. Connect the normally open contacts of the flow switch in the unit control center at
terminals 5 and 6. There is also a set of normally closed contacts on the switch that can be used for
an indicator light or an alarm to indicate when a “no flow” condition exists. Freeze protect any flow
switch that is installed outdoors.
NOTE: Differential pressure switches are not recommended for outdoor installation.
Bring water piping to the cooler from the bottom of the unit or through the side between the vertical
supports.
8IM 676
Page 9
Note: The procedure
does not specify the
type of glycol. Use
the derate factors
found in Table 4 for
corrections when
using ethylene glycol
and those in Table 5
for propylene glycol.
Note: On units sizes 160E through 185E there is a diagonal bracket off of a vertical support
which will interfere with the water connection if brought in from the side. This brace can be
removed, but only after the unit is in place.
Refrigerant Charge
All units are designed for use with HCFC-22 and other refrigerants. See nameplate for specific
refrigerant used. Units are shipped with an operating charge. The operating charge
(using HCFC-22) for each unit is shown in the Physical Data tables beginning on page 12.
Glycol Solutions
The system glycol capacity, glycol solution flow rate in GPM, and pressure drop through the cooler
may be calculated using the following formulas and table.
1. Capacity -- Find the reduced capacity by multiplying the chiller’s capacity with water by the
capacity correction factor C.
2. Flow -- To determine evaporator gpm (or Delta-T) knowing Delta-T (or gpm) and capacity:
×
Glycol GPM (from table)=
24capacity glycol
DeltaT
For Metric Applications -- To determine evaporator L/s (or Delta-T) knowing Delta-T (or L/s)
and kW:
Glycol L / s(from table)=
4. 18
kW
×−
DeltaT
3. Pressure drop -- To determine pressure drop through the evaporator, when using glycol, enter
the water pressure drop curve on page 11 at the actual glycol GPM. Multiply the water pressure
drop by PD correction factor from Table 4 or Table 5 to obtain corrected glycol pressure drop.
4. To determine the unit's power consumption when using glycol, multiply the water system kW by
factor kW.
Test coolant with a clean, accurate glycol solution hydrometer (similar to that found in service
stations) to determine the freezing point. Obtain percent glycol from the freezing point table below.
On glycol applications it is normally recommended by the supplier that a minimum of 25% solution
by weight be used for protection against corrosion.
()
−
×
Flow
×
G
IM 6769
Page 10
CAUTION
Do not use an automotive grade antifreeze. Industrial grade glycols must be used.
Automotive antifreeze contains inhibitors which will cause plating on the copper tubes
within the chiller evaporator. The type and handling of glycol used must be consistent with
local codes.
Evaporator flow rate must fall between the minimum and maximum values shown in the evaporator
pressure drop curve. Flow rates below the minimum values will result in laminar flow which will
reduce efficiency, cause erratic operation of the expansion valve and could cause low temperature
cutouts. Flow rates exceeding the maximum values can cause erosion on the evaporator water
connections and tubes.
Measure the chilled water pressure drop through the evaporator at field installed pressure taps.
It is important not to include the effect of valves or strainers in these readings.
Varying chilled water flow through the evaporator while the compressor(s) are operating is not
Unit Capacity @ ARI Conditions (1), Tons (kW)139.7 (491.2)144.7 (508.8)149.9 (527.0)157.8 (554.8)
Number Of Refrigerant Circuits2222
Unit Operating Charge, R-22, Lbs125125130130130130140140
Unit Operating Charge, R-22, (kg)(45.4)(45.4)(45.4)(45.4)(45.4)(45.4)(49.9)(49.9)
Cabinet Dimensions, LxWxH, In.229 x 83 x 93229 x 83 x 93229 x 83 x 93263 x 83 x 93
Cabinet Dimensions, LxWxH, (mm)(5809 x 2118 x 2369)(5809 x 2118 x 2369)(5809 x 2118 x 2369)(6690 x 2118 x 2369)
Unit Operating Weight, Lbs. (kg)10440 (4736)10690 (4849)10850 (4922)11515 (5223)
Unit Shipping Weight, Lbs. (kg)10040 (4554)10290 (4668)10450 (4740)11115 (5042)
Number Of Fans - Fan Diameter, In. (mm)14 - 28 (711)14 - 28 (711)14 - 28 (711)
Number Of Motors - HP (kW)14 - 1.5 (1.1)14 - 1.5 (1.1)14 - 1.5 (1.1)
Fan And Motor RPM, 60/50Hz1100/9151100/9151100/915
60 Hz Fan Tip Speed, FPM806380638063
60 Hz Total Unit Airflow, CFM126280126280126280
DIRECT EXPANSION EVAPORATOR - BAFFLED SHELL AND THRU-TUBE
Diameter, in. - Length, Ft.18 - 1018 - 1018 - 10
Diameter, (mm) - Length, (mm)(457 - 3048)(457 - 3048)(457 - 3048)
Water Volume, Gallons, (L)57.30 (216.9)57.30 (216.9)57.30 (216.9)
Maximum Water Pressure, psig (kPa)175 (1207)175 (1207)175 (1207)
Maximum Refrigerant Working Pressure, psig (kPa)225 (1552)225 (1552)225 (1552)
Water Inlet / Outlet Victaulic Connections, In. (mm)6 (152.4)6 (152.4)6 (152.4)
Drain - NPT int, In. (mm).375 (9.5).375 (9.5).375 (9.5)
Vent - NPT int, In. (mm).375 (9.5).375 (9.5).375 (9.5)
NOTE:
1. Nominal capacity based on 95F ambient air and 54F/44F water range.
(2032 x
6172)
(2032 x
6172)
(2032 x
6172)
(2032 x
6172)
(2032 x
6172)
IM 67617
Page 18
Electrical Data
Field Wiring
CAUTION
Internal power wiring to the compressors for single and multiple point option are different. Field wiring must be
installed according to unit wiring diagram.
Wiring must comply with all applicable codes and ordinances. Warranty is void if wiring is not in accordance with
specifications. Copper wire is required for all power lead terminations at the unit. Aluminum or copper can be used for all
other wiring.
ALR units may be ordered with internal power wiring for either single or multiple point power connection. If single
point power connection is ordered, a single large power terminal block is provided and wiring within the unit is sized in
accordance with the National Electrical Code. A single field supplied fused disconnect is required. An optional factory
mounted transformer may be installed.
If multiple point power wiring is ordered, three power connections, one per compressor circuit, one for condenser fans,
and control circuit, are required. Separate field supplied fused disconnects are required for each of the three circuits. A
single power block is provided for all of the condenser fans and the optional 115V control transformer.
If the evaporator heater is on a separate disconnect switch from the main unit power supply, the unit may be shut down
without defeating the freeze protection provided by the cooler heater.
18IM 676
Page 19
Table 13, 032E - 070E Electrical Data Single Point
* There are 2 power blocks, each having 840 terminal amps. (1680 total terminal amps)
See page 33 for all other Electrical Data notes.
IM 67631
Page 32
Table 27, 032E - 075E Field Wiring Data, Multiple Point Power
ALRWiring to Standard Power Block
UnitVoltsHZ.Terminal AmpsConnector Wire Range (Copper Wire Only)
SizeCircuit 1Circuit 2Circuit 3Circuit 1Circuit 2Circuit 3
Table 28, 080E - 185E Field Wiring Data, Multiple Point Power
ALRWiring to Standard Power Block
UnitVoltsHZ.Terminal AmpsConnector Wire Range (Copper Wire Only)
SizeCircuit 1Circuit 2Circuit 3Circuit 1Circuit 2Circuit 3
Notes for “Electrical Data Single Point” and “Electrical Data Multiple Point” Power:
1. Unit wire size ampacity (MCA) is equal to 125% of the largest compressor-motor RLA plus 100% of RLA of all other
loads in the circuit including the control transformer.
2. If the control transformer option is furnished, no separate 115v power is required.
3. If a separate 115V power supply is used for the control circuit, then the wire sizing amps is:
• 10 amps for unit sizes ALR032E through ALR075E
• 12 amps for unit sizes ALR080E through ALR185E
4. Recommended power lead wire sizes for 3 conductors per conduit are based on 100% conductor ampacity in
accordance with NEC. Wire sizes for 6 conductors per conduit are based on 80% conductor ampacity in accordance
with NEC. Voltage drop has not been included. Therefore, it is recommended that power leads be kept short. All
terminal block connections must be made with copper (type THW) wire.
5. The unit power terminal block may have 2 lugs per phase. Single or parallel conductors should be used for power
connections as listed under “Recommended Power Lead Wire Size.”
6. “Recommended Fuse Sizes” are selected at approximately 150% of the largest compressor RLA, plus 100% of all other
loads in the circuit.
7. “Maximum Fuse Sizes” are selected at approximately 225% of the largest compressor RLA, plus 100% of all other
loads in the circuit.
8. The recommended power lead wire sizes are based on an ambient temperature of 86° F. Ampacity correction factors
must be applied for other ambient temperatures. Refer to the National Electrical Code Handbook.
Voltage Limitations:
Unit Nameplate - 208V/60Hz/3Ph: 187V to 253V (except ALR060E through ALR155E: 187V to 220V)
Unit Nameplate - 230V/60Hz/3Ph: 187V to 253V (except ALR060E through ALR155E: 207V to 253V)
Unit Nameplate - 460V/60Hz/3Ph: 414V to 506V
Unit Nameplate - 575V/60Hz/3Ph: 517V to 633V
Notes for “Compressor and Condenser Fan Amp Draw”:
1. Compressor RLA values are for wiring sizing purposes only but do not reflect normal operating current draw at rated
capacity. If unit is equipped with SpeedTrol condenser fan motors, the first motor on each refrigerant circuit is a single
phase, 1hp motor, with a FLA of 2.8 amps at 460 volts, 5.6 amps at 208, 230, and 575 volts.
2. Compressor LRA for reduced inrush start are for the first winding only. If the unit is equipped with SpeedTrol motors,
the first motor is a single phase, 1 hp motor, with a LRA of 7.3 amps at 460 volts, 14.5 amps at 208, 230 and 575 volts.
Notes for “Field Wiring Data” - Both Single and Multiple Point Power:
1. Single point power supply requires a single disconnect to supply electrical power to the unit. This power must be
fused.
2. Multiple point power supply requires two independent power circuits each with separate disconnects and a separate
control circuit.
3. All field wiring to unit power block or optional non-fused disconnect switch must be copper.
4. All field wire size values given in table apply to 75° C rated wire per NEC.
34IM 676
Page 35
Figure 7,ALR 032E through 185E, typical field wiring diagram
IM 67635
Page 36
Dimensional Data
Figure 8, 032E through 100E Dimensions
ALREVAPORATOR WATER CONNECTIONSCENTER OF GRAVITYISOLATOR LOCATIONNUMBER
ALREVAPORATORCENTER OF GRAVITYISOLATOR LOCATIONNUMBER
UNIT"A"CONN.WATER CONNECTIONSXYRSTOF
SIZELENGTHSIZE (1)BCEFANS
110E
120E
130E
135E
140E
145E
150E
160E
170E
180E
185E
229 (5817)6 (152.4)117.6
(2987)
229 (5817)6 (152.4)118.5
(3010)
229 (5817)6 (152.4)118.5
(3010)
229 (5817)6 (152.4)118.5
(3010)
229 (5817)6 (152.4)118.5
(3010)
229 (5817)6 (152.4)118.5
(3010)
229 (5817)6 (152.4)118.5
(3010)
263 (6680)6 (152.4)153.2
(3891)
263 (6680)6 (152.4)153.2
(3891)
263 (6680)6 (152.4)153.2
(3891)
263 (6680)6 (152.4)153.2
(3891)
13.8 (351) 19.5 (495)106.5
(2705)
12.9 (328) 19.5 (495)106.5
(2705)
12.9 (328) 19.5 (495)107.0
(2718)
12.9 (328) 19.5 (495)105.0
(2667)
12.9 (328) 19.5 (495)108.0
(2743)
12.9 (328) 20.5 (521)103.0
(2616)
12.9 (328) 20.5 (521)105.0
(2667)
47.6 (1209) 20.5 (521)121.0
(3074)
47.6 (1209) 20.5 (521)119.0
(3023)
47.6 (1209) 20.5 (521)118.0
(2997)
47.6 (1209) 20.5 (521)118.0
(2997)
41.7 (1059)13 (330)58 (1473) 215 (5461)10
41.7 (1059)13 (330)58 (1473) 215 (5461)10
41.7 (1059)13 (330)58 (1473) 215 (5461)12
41.7 (1059)13 (330)58 (1473) 215 (5461)12
41.7 (1059)13 (330)58 (1473) 215 (5461)12
41.7 (1059)13 (330)58 (1473) 215 (5461)12
41.7 (1059)13 (330)58 (1473) 215 (5461)12
41.7 (1059)13 (330)95 (2413) 250 (6350)14
41.7 (1059)13 (330)95 (2413) 250 (6350)14
41.7 (1059)13 (330)95 (2413) 250 (6350)14
41.7 (1059)13 (330)95 (2413) 250 (6350)14
IM 67637
Page 38
Unit Layout and Principles of Operation
Figure 10, Major component locations
The figure below illustrates component locations for each unit size.
Control Center
All electrical controls are enclosed in a weatherproof control center with keylocked, hinged access
doors. The control center has two separate compartments, high voltage and low voltage. All high
voltage components are located in the compartment on the right side of the unit.
The low voltage components are located on the left side with the live terminals behind the
deadfront panel. This protects service personnel from live terminals when accessing the adjustable
and resettable controls.
Control center layouts ALR 032E through 75E
Figure 11, Left side, 115V control sectionFigure 12, Right side, high voltage power
section
Note: PB1, PB2, PB3 are used with multiple point power wiring
38IM 676
Page 39
Control center layouts ALR 080E through 185E
Stationary Panel
6" (152mm) Min.
Figure 13, Left side, 115V control sectionFigure 14, Right side, high voltage power
section
Note: PB1, PB2, PB3 are used with multiple point power wiring
Figure 15,Recommended field installed unit disconnect location
Hinged Doors on
Control Center
9.5"
(241mm)
Min.
Disconnect Switch
Power
Into
Unit
Note: Mount disconnect on stationary panel so it does not interfere with hinged doors or
with air intake into coil.
IM 67639
Page 40
Start-up and Shutdown
Pre Start-up
1. Open all electric disconnects and check all electric connections for tightness. Check all
compressor valve connections for tightness.
2. Inspect all water piping for flow direction and correct connections at the evaporator.
3. Verify thermostat water temperature sensor is installed in the leaving water line (supply to
building). On all ALR units the sensor well and sensor are factory mounted.
4. Check compressor oil level. The oil level should be visible in the oil sightglass.
5. Check voltage of the unit power supply and make certain voltage is within ±10% of nameplate
rating.
6. Check unit power supply wiring for proper ampacity and a minimum insulation temperature of
75°C.
7. Verify all mechanical and electrical inspections have been completed according to local codes.
8. Verify all auxiliary control equipment is operative and an adequate cooling load is available.
9. Open compressor suction and discharge shutoff valves until backseated. Always replace valve
seal caps.
10. Open control stop switch S1(off) and place pumpdown switches PS1 and PS2 on “manual
pumpdown,”. Turn on the main power and control disconnect switches. This will energize
crankcase heaters. Wait at least 12 hours before starting up unit.
11. Open all water flow valves and start the chilled water pump. Check all piping for leaks and
vent the air from the evaporator as well as from the system piping. Flush the evaporator and
system piping to obtain clean, noncorrosive water in the evaporator.
NOTE: If LWC1 is a Unit 33 Metasys control, the control must be energized before the
chilled water flow switch is closed.
CAUTION
Most relays and terminals in the unit control center are energized with S1 and the control
circuit disconnect on. Do not close S1 until start-up.
Start-up
1. Verify compressor suction and discharge shutoff valves are backseated. Always replace valve
seal caps.
2. Open oil equalization line valve (ALR 080E through 185E only).
3. Open manual liquid line shutoff valve at the outlet of the condenser subcooler.
4. Set temperature controller LWC1 to the desired chilled water temperature. Set the control
band.
5. Start auxillary equipment by turning on the following:
§ Time clock
§ Ambient thermostat and/or remote on/off switch
§ Chilled water pump.
6. Verify pumpdown switches PS1 and PS2 are in “manual pumpdown” (open) position. If
pressures on the low side of the system are above 60 psig (414 kPa), the unit will start and
pump down.
40IM 676
Page 41
7. After compressor lockout timer TD1 has timed out, start the system by moving pumpdown
switches PS1 and PS2 to “auto pumpdown” position.
8. After running the unit for a short time, check the following:
§ Oil level in each compressor crankcase
§ Rotation of fans
§ Flashing in refrigerant sightglass.
9. Verify superheat temperature is at the factory setting of 8 to 12 degrees F (4.4 to 6.7 degrees C).
10. After system performance has stabilized, complete the “Compressorized Equipment Warranty
Form” (Form No. 415415Y) to obtain full warranty benefits. Return the form to McQuay
International through your sales representative.
Sequence of Operation
The following sequence of operation is typical for ALR SeasonPak air-cooled water chiller, Models
ALR 032E through ALR 185E (items in italics apply only to Models ALR 080E through 185E).
The sequence varies depending upon options.
Start - up
With the control circuit power on and the control stop switch S1 closed, 115V power is applied
through the control circuit fuse F1 to the compressor crankcase heaters HTR1 and HTR2 (HTR3 andHTR4), the compressor motor protections MP1 and MP2 (MP3 and MP4), and the primary of the
24V control circuit transformer. The 24V transformer provides power to the contacts of the low
pressure controls LP1 and LP2 and the compressor lockout timer TD1 and TD2.
When the remote time clock or manual shutdown switch turns on the chilled water pump, the
flow switch closes and 115V power is applied to the relay contacts on the leaving water control
LWC1. The unit will automatically operate in response to the LWC1 if the manual pumpdown
switches PS1 and PS2 are closed ( in the “auto” position); the compressor lockout time relays R5
and R6 (R7 and R8); and the freezestats FS1 and FS2, high pressure controls HP1 and HP2, and the
compressor motor protectors MP1 and MP2 (MP3 and MP4) do not sense failure conditions.
On a call for cooling, the leaving water control LWC1 completes the circuit to the liquid line
solenoid valve SV1 for refrigerant circuit #1, opening the valve and allowing refrigerant to flow
through the expansion valve and into the evaporator. As the evaporator refrigerant pressure
increases, the low pressure control LP1 closes. This energizes the compressor starting relay R9,
starting the compressor via the compressor contactors M1 and M5. Closing the R9 contacts also
energizes the condenser fan motor contacts M11 and M12 starting the fan motors.
As additional stages of cooling capacity are required, the leaving water control LWC1 energizes
the liquid line solenoid valve SV2 of the refrigerant circuit #2. After the compressor sequencing
time delay TD11 has closed, the same starting sequence is initiated in refrigerant circuit #2.
If still more cooling is required, the leaving water control will start the remaining compressors
and then de-energize unloader solenoids until the capacity requirement is met.
IM 67641
Page 42
Pumpdown
As the leaving water control is satisfied, it will unload the compressor(s) and then de-energize the
liquid line solenoid valve(s) SV1 and SV2, causing the valve(s) to close. When the compressor has
pumped most of the refrigerant out of the evaporator and into the condenser, the low pressure
control(s) LP1 and LP2 will open. If the refrigerant leaks into the low side causing the pressure to
close the low pressure controls LP1 and LP2, the compressor will start after a two-hour time delay.
For normal temperature controlled operation, the timer is bypassed and the compressor will start on
a refrigerant pressure rise.
Note: Do not shut the unit down without going through the pumpdown cycle. Flow switch,
time clock, and ambient lockout thermostat must be wired to allow pumpdown when unit is
turned off.
.
42IM 676
Page 43
Page 44
13600 Industrial Park Boulevard, P.O. Box 1551, Minneapolis, MN 55440 USA (612) 553-5330
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