Gulf+Western ACWC-SC User manual

MODEL ACWC-SC
Screw Type
AIR
COOLED
PACKAGED CHILLERS
SERVICE MANUAL
I & 0 6500A
INSTALLATION, OPERATION
&
MAINTENANCE INSTRUCTIONS
TABLE OF CONTENTS
DESCRIPTION PAGE NO.
Inspection & Handling ........................................................................................... 2
Location & Mounting . ....... ... ...... ............................................... ................... . ..... .... 2
Wiring .............................................................................................................. 2
Chiller Piping ..................................................................................................... 2
Start-Up ........................................................................................................ 2 & 3
Maintenance .... . .... . ....... ..... ........... . ........ . ............. ... .... .... ........ .. ......................... 3
Slide Valve
Unloading System .................................................................................. 4
Low Ambient Operation ......................................................................................... 5
Control Settings .................................................................................................. 5
Unit Operating Limitations ...................................................................................... 5
Sequence of Operation ...................................................................................... 6 & 7
Models ACWC-160SC Thru 200SC
Sequence of Operation ...................................................................................... 8 & 9
Model ACWC-215SC
Control Wiring Diagram .................................................................................. 10 & 11
Models ACWC-160SC Thru 200SC
Control Wiring Diagram .................................................................................... 12-15
Model ACWC-215SC
Power Wiring Diagram ............. .... .... ... .. ... .... .. ..... . ... .. .... .. ....... ...................... . ........ 16
Across-The-Line Start
Power Wiring Diagram .......................................................................................... 17
Star-Delta
Electrical Data ................................................................................................... 18
Cooler Pressure Drops .......................................................................................... 18
Unit Loading/Suspension Points .............................................................................. 18
Troubleshooting Guide .... .. ........... .... ........... ... .......... . ........... ..... ..... .. .... ... ............ .19
Causes & Prevention of Freeze-Up ............................................................................ 19
Start-Up Check List ..................................... . ..... .. .. ... . .......................................... 20
Operating Data ... ..... ........... .... . ... .... ..... .. ................ . ...... ........................... ... ...... .. 20
BOHN HEAT TRANSFER
A Gulf+Western Company
Danville, Illinois 61832•{217)446-3710
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I

INSPECTION & HANDLING
When unit is received, it should be checked for visible or concealed
damage . If damage has occurred it should be reported to the carrier
imm e diately . o.nd clo.im filed .
Models ACWC 160SC thru 215SC are factory mounted on two (2)
permanent angle beam, carbon steel skids. Ei ght (8) 2W' lifting eyes
are
provided in the skids to allow rigging. Spreader bars must be
used between
rigging lines to prevent damage to the unit. Rollers
may be used
under the skids to facilitate moving the unit a short
distance . Physical damage to the unit, after acceptance, Is not the
responsibility of the factory.
LOCATION & MOUNTING
Model ACWC Air Cooled Packaged Water Chillers are designed for
outdoor application and may be mounted on roof or at ground level.
Air flow through the condenser is vertical and the unit may be
located adjacent to outside of building or on roof without regard for
prevailing wind direction.
Since these units are air cooled, the flow of air to and from the
condenser coil must not be impeded. There must be no obstruction
above the unit that would tend to deflect discharge air downward
where it could be recirculated back to the inlet of the unit. The
required overhead air space should be a minimum of eight (8) feet.
Ductwork must not be applied to the fan outlets .
The
unit must be installed with sufficient clearance for air entrance
to the condenser coil and for servicing access. The unit should be
located
no closerthan four (4) feet from any wall or other obstruction .
Clearance must be provided at either end of the unit to permit
removal of tubes from the chiller .
Unit must be set on a solid and level foundation .
On roof installations the unit should be mounted on support beams
which span load-bearing walls to prevent excessive vibration .
On ground level installations, the unit should be mounted on a
substantial base that will not settle. A one-piece concrete slab with
footings extended below the frost line is recommended. A space
should be left between the slab and the building to prevent the
transmission of sound and vibration .
Vibration mounts may be used for roof mounted units or other
locations where noise might be objectionable.
WIRING
A unit wiring diagram showing the required power supply character-
istics and all factory supplied wiring details is provided with unit.
Separate, field
supplied, disconnects must be installed in the power
supply and should be within the sight of the unit.
Separate 115
volt power source must be field supplied to provide
power for control and heater circuits .
2
CHILLER PIPING
The chiller inlet (return) water pipe should be connected to the water
connection closest to the control panel end of the unit and the outlet
(:.upply) vvdte• 1-'ifJt:: <..v""""'t"'u tv u,., wat.,r <,;urrrr.,<,;llun on the
opposite end of the cooler(s).
A
flow switch must be installed in a straight horizontal section of the
chilled water piping .
Gauges
should be installed in the piping to and from the chiller to
measure
the pressure drop and to insure the proper (GPM) flow rate
in
accordance with submittal data. A strainer should be installed in
the piping on the inlet side of the chiller and vibration eliminators
should be employed on both the inlet and outlet pipes. Air vents
should be located at all high points in the piping system. Vents
should be located to be accessible to servicing .Drain connections
should be provided at all low points to permit complete drainage of
chiller and piping system.
The chilled water piping should be insulated to reduce heat pickup
and to prevent condensation . If the system is for year-round
operation or if it will not be drained in the winter, the chilled water
piping should be protected againstfreezing by electric heating cable
or other suitable means.
Upon completion of chiller piping, start the system water pump and
purge air from the system. Air purging should be done from the high
points in the water circuit. Purging of the chiller barrel may be
accomplished through the vent pipe located on the top of the chiller
compartment. Failure to purge air from the water circuit will result in
inadequate waterflow and maycause the unit to cutout on low water
flow freeze protection.
START-UP
Refer to start, test, and check list included with this manual.
Check all electrical and mechanical connections for shipping
looseness and tighten all screws on electrical terminals .
Activate the 115
volt chiller and crankcase heater circuit 24 hours
prior to unit start-up .
Rotateeach fan
prior to start-up . Fans should turn freely. Check belt
tension and pulley alignment. After two (2) weeks of operation,
readjust
belt tension to accommodate for belt stretching.
Check all control settings as specified in Table 1.
Check the compressor oil level through the crankcase sight glass.
The oil level should be to the top of the glass. If the level is low, add
oil in
accordance with the directions in the maintenance instruction
(page 3).
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. CAUTION:
The discharge line valve must be open before starting the compres-
sor . Liquid line valves must also be open for sustained operation .
All compressorsare solia mountea on 1sopads,therefore, compressor
hold-down bolts must not be loosened. Loosening these bolts will
cause excessive vibration of the compressor and may result in
refrigerant line breakage. Prior to start-up check all compressor
hold-down bolts for tightness.
MAINTENANCE
CONDENSER
Units equipped with belt drive fans have inherently protected
motors . Fan belts,fan bearings and motor bearings require periodic
maintenance as follows:
1. Fan Belts -After two (2) weeks operat i on , the belts will have
nearly reached their permanent stretch, therefore , each belt
should be checked again and proper adjustments made. To
maintain good fan and motor operation ,the belt tension should be
checked at three (3)
month intervals.
2. Fan Bearings- Each fan shaft is prov i ded with ball bearings of
the relubricatable type . Each bearing is provided with grease
fittings, accessible through the individual motor access panels. It
is
recommended the bearings be greased by adding 4 to 5 shots
with a hand gun .The suggested greasing interval is indicated on a
sticker attached to the unit.
3. Motor Bearings- Each motor is equipped with ball bearings. Ball
bearings
consume a very small amount of lubricant , but enough
must be present at all time to prevent motor injury. The length of
time a bearing can run without having grease added or replaced
will depend upon the operating conditions . Under normal
operating conditions ,the motor bearings should be lubricated at
2000
hour operating intervals . The lubricant should be from a
clean closed
container and should be an anti-friction type bearing
grease-free
from solid fillers or other harmful ingredients .
Lubricant should have a safe operating temperature of 2000° F.
The air inlet of the condenser coil should be kept clean through a
regular preventative maintenance program .
COMPRESSOR
1. OIL LEVEL - The oil level in the compressor(s) should be
checked periodically, with the compressor either running or
stopped . If the oil level is below one-half ( '12 ) the sight glass, oil
must be added.
Oil should be added only with the compressor shut off . To do so,
turn the return water thermostat (T1) to a higher temperature
setting , and wait for the unit to pumpdown and shutoff. Place the
system "
ON-OFF " switch in the "OFF" position . Close the line
valve in the
discharge line between compressor and condenser .
Refrigerant pressure inside of the compressor will now be
approximately 80 to 90 PSIG. The low pressure cut-out setting is
35 PSIG,
but the residual discharge pressure (upstream of the
discharge check valve) will equalize back into the suction side
after the compressor stops.
3
Locate the discharge pressure port adjacent to solenoid valve
UL-3 (see drawing below) ; remove the cap and release the
residual pressure
by pushing in on the pressure port fitting itself.
Pump oil into this flU' t u11til u,., uil level Is to the tOP Of the sight
glass.
Replacethe
discharge port cap . Re-open the discharge line valve.
Do not allow compressor to run with discharge valve closed.
Place the system "ON-OFF" switch in the " ON " position . Using a
jumper wire, makea "short " for five (5) seconds between terminal
#4 on terminal block TER5 and the switched terminal of a solenoid
valve feeding the circuit you have just "blown " (e.g. terminal #121
on TER4 to energize SOL 1).Reset return water thermostat (~1) to
the operat ional temperature setting and allow unit to return to
normal operation .
2. RECOMMENDED OIL- The unit is factory-charged with BOHN
SR-30 refrigeration oil.
Do not add any other type of oil to this factory charge.
Do not operate compressor
If oil level is below one-half ('h) sight
glass.
If the oil level is below the minimum specified above, and BOHN
SR-30 is not on hand, you may drain the entire factory oil charge,
then refill with SUNISO 4GS refrigeration oil. The factory (BOHN)
oil is of the synthetic type and will not mix with SUN ISO 4GS. Do
not attempt to operate the screw compressor with any oil other
than these two specified above.
It is suggested that a gallon or more of BOHN SR-30 oil be
obtained and kept on hand at the job site. The substitution of
SUNISO 4GS oil, as outlined above, will result in a 2% to 4%
capacity loss, and no reduction in input K.W.
3. COMPRESSOR REPAIRS (Internal) - Contact factory or an
authorized BOHN Service Agency if a compressor malfunction is
suspected.
4. COMPRESSOR REPAIRS (External) - Proper operation of
unloaded start, loading , and unloading is controlled by solenoid
valves UL-1 ,
UL-2 and UL-3. Any of thesethree (3) solenoid valves
may be repaired
or replaced in the field, as required.
HIGH PRESSURE
PORT

SLIDE VALVE
UNLOADING SYSTEM
1ne tlonn screw compressor capacity control system for infinite
modulation consists of a slide valve and hydraulic piston / cylinder
operator internal to the compressor; plus three hydraulic solenoid
valves (UL-1, UL-2 & UL-3) piped externally.
The slide valve forms a portion of the chamber wall in which the
rotors turn; thus, its position with respect to the rotors determines
the effective rotor length and thereby the percent of full load
capacity .
Upon compressor start-up , UL-3 is opened. This allows oil pressure
to act upon the hydraulic piston, holding it in the fully unloaded
position . After 30 seconds, during which time full oil flow is
established to all bearings surfaces, UL-3 is closed . At this point, the
temperature controller is free to open and close UL-1 or UL-2 in
response
to the supply water temperature .
The
slide valve will move to the left (loading) by force of discharge
pressure , whenever UL-1 opens to permit flow to the oil return (low
Load Unload
¢::J
c::>
Oil Pressure
Slide Valve
Oil Pressure Lines
Screw
Rotor
pressure) line. The slide valve will move to the right (unloading)
whenever UL-2 opens the oil supply (high pressure) line, since the
force of the oil exceeds that of the discharge gas.
The temperature controller sends a series of power (energizing)
" pulses " to the appropriate solenoid to adjust to load conditions .
The further the supply water temperature is from the controller set
point, the longer is the duration of the pulses. The series of pulses
will continue until the controller is satisfied. As the water temperature
approaches the set point , the pulses become quite brief to prevent
overshooting the set point.
This method of compressor unloading in conjunction with supply
water sensing minimizes action / reaction lag time and overshoot
resulting in an exceptionally precise and stable control of supply
water temperature .
UL-1
Oil
Return
Hydraulic Piston
Oil
Supply
Vent to
Suction
The following table lists solenoid valve position for all three
operating modes.
UL-1 UL-2 UL-3
Starting
Close Close
Open
Loading
Open Close
Close
Unloading
Close Open Close
4
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LOW AMBIENT OPERATION
Due to the wide range of applications, it is sometimes necessary to
operate the Air Cooled Packaged Water Chillers at ambients below
summer conditions. Without proper control, when ambients drop
below 60° F. the pressure differential between the condenser and
the evaporator is below the level to insure proper thermal expansion
valve operation . As a result, the unit may cycle on low pressure
control with the possibility of evaporator freezing. Three types of
system control are available allowing the units to operate at the
ambients indicated:
FAN CYCLING
MEDIUM AMBIENT CONTROL TO 30° F.
(STANDARD EQUIPMENT -FACTORY INSTALLED)
A fan cycling control is standard on all Air Cooled Packaged Water
Chillers to prov1de prop er operating head pressures, in ambient
conditions to 30° F.
This is an automatic operation in which the condenser fans are
cycled on and off , as required, in response to head pressure. With
two compressors running , three fans are cycled (in sequence) on
five-fan units; four fans on six-fan units ; and five fans on seven-fan
units. With one compressor running, all but the lead fan are cycled in
sequence, in
response to head pressure.
This arrangement provides positive start-up control down to +30° F.
by delaying the condenser fan operation until a predetermined head
pressure is obtained.
GRAVITY (Discharge) DAMPERS
LOW
AMBIENT CONTROL TO oo F.
(OPTIONAL EQUIPMENT- FACTORY INSTALLED)
All condenser fans are equipped with gravity dampers mounted on
the fan discharge to minimize the effect of prevailing winds; and to
prevent convection drafts up through the condenser coil in still air.
All
compressors are enclosed in individual insulated housings. An
auxiliary heater is included to supplement the standard crankcase
heater ; the temperature within the compressor compartment is
thermostatically controlled .
The standard condenser fan cycling package, operating in con-
junction with the discharge dampers , will maintain suitable head
pressure down to oo F. ambient. A 90-second time delay relay
provides an electrical bypass around the low pressure freezestat to
prevent nuisance tnp-out during cold start-up.
ACWC-SC
CONTROL SETTINGS
PRESSURE ACTUATED
LEGEND
FACTORY SETTING
High Pressure Control HP-1 Cut-In
300 PISG
(Manual Reset) HP2 & HP3 Cut-Out
365 PSIG
Pumpdown Control PD1 Cut-In
55 PSIG
(Auto Reset) PD2 & PD3
Cut-Out
35 PSIG
Fan
Cycling Pressure Control
2 Fan Cell
Cut-In (PSIG)
Cut-Out
(Adjustable)
FCP 1 280 170
FCP 2 295 180
3 Fan
Cell
FCP 1 260 160
FCP 2 275 175
FCP 3 290 215
4 Fan Cell
FCP 1 260 160
FCP 2 275 175
FCP3 285 210
FCP4 295 235
Low Pressure Freeze Control LPF 1
Cut-Out
54 PSIG
(Manual Reset)
--
LPF 2 & LPF-3
TEMPERATURE ACTUATED LEGEND
FACTORY SETTING
Chiller Low Water Temperature Thermostat
T2
Cut-Out 37° F.
Chiller Water Cycling Thermostat (Adjustable)
T1
Dial Set At 55° F.
Chiller Heater Thermostat
Included With
Cut -In 40° F.
(Non-Adjustable
CBH1 Heater
Cut-Out
45° F.
Oil Temperature Safety Control OTS 1
(Adjustable)
OTS 2
Cut-Out
240° F.
Manual Reset
OTS3
Capacity Control Thermostat (Adj.) Mode Control Position T3
Dial Set At
44° F.
UNIT OPERATING LIMITATIONS
1. Maximum ambient air to condenser is 115° F. (60 Hertz operation).
2. Maximum allowable cooler water pressure is 150 PSIG.
3. Maximum allowable water temperature to cooler is 75° F.
4. Units must not have leaving water temperatures of 42° F. or lower unless used with a glycol solution.
5. Unit must be allowed to pumpdown at the end of each operating cycle (except on safety control shutdown).
5

KEY TO WIRING DIAGRAM INDEXING SYSTEM
The wiring diagrams and sequence instructions on the following pages have been devised to simplify the understanding and tracing of circuit
theory. The following key shows how the indexing system can be used.
12
Line number on wiring diagram
[12] Line number in text
(RS) Component identification symbol in text (Relay #5)
~ Normally open contact- line number location
~ Normally closed contact- line number location
@ Holding coil - line number location
& Note number
EXAMPLE
30
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SEQUENCE OF OPERATION
MODELS ACWC 160 To 200 SC
The following sequence of operation is typical for the ACWC 160 to
200 SC (see Pages 10 and 11 for typical wiring diagram). Refer to the
wiring diagram furnished with unit for specific information.
Control Identification Symbol
Circuit Line Number
Important Notel
The compressor crankcase heater must be energized and remain
active for a minimum fa 24 hours prior to unit start-up.
PRELIMINARY SEQUENCE
Place control circuit "ON-OFF" switches (SW1 thru SW4) in the
"OFF" position, and set the staging thermostat (T1) to its highest
temperature.
Activate the 115 volt electrical service to terminals #2 and #4 [1 and
3] on
terminal board (TEAS) to distribute power to the control circuit
up to the control circuit switches. Crankcase heater relay contacts
(R19) (3]. (R20) [5]. and (R21) [7] are closed and are supplying
power to the compressor crankcase heaters. Power is also supplied
to the chiller barrel heater (CBH1) (11]. the receiver heaters (RH1, 2,
3) (8, 9, 10] (optional), and the low ambient crankcase heaters
(SCH1,
2, 3) [3, 5, 7] (optional).
Close the main power disconnect switch. Check to see that the red
indicating light on the phase loss monitor (PLM1) is lit (NOTE: There
will be two phase loss monitors, (PLM1) and (PLM2),
on 208-230 volt
models).
This light must be on to indicate proper phase rotation for
the compressor(s) . If the light is not on, the main control circuit to
the compressors will not be energized. Reverse any two phase legs
at
the Main Incoming Power Terminal Block. DO NOT reverse the
leads on the phase loss monitor, for this will allow the compressor to
run backwards, causing severe damage, and WILL VOID THE
COMPRESSOR WARRANTEE!
Start-up the chilled water pump. The water flow is confirmed when
the water flow switch completes an electrical circuit across terminals
#12 (58] and #13 [60] of terminal board (TEAS). Terminals #14 [61]
6
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See Note Number 3
The holding coil for the first contact shown on this
line (reading from left to right) can be found on line
#44; the holding coil for the second contact can be
found on line #74.
The contacts for the holding coil shown on this line can be found on
lines 66, 23, and 54. The contact on line 23 is normally closed .
This is the number which identifies the line of wiring shown at the left.
and #15 [63]
provide an interlock for the water pump starter(s);
either contact (R14). (R16), or (R18) [62] will close any time a
compressor is running.
Set the staging thermostat (T1) to the design range of operation (e.g.
54°
F. return water). Set the capacity control thermostat (T3) to the
design range of operation (e.g. 44° F. supply water).
Place
the four (4) control circuit switches (SW1-SW4) in the "ON"
position , thus energizing the balance of the control circuit. The
system will
be In the "Time-In" mode for five minutes before any
compressor will start.
STAGE 1
LOADING
Upon demand for cooling, the first step of the staging thermostat
(T1) will close , energizing relay (TD10) (63] and staging relay (R1)
[62].
closing (R1) contacts 7-4 [22]. 8-5 [25]. and 9-6 (16]. If the
safety controls and switches are closed, the control circuit [16] for
compressor No.1 and liquid line solenoid (SOL 1) (25] will energize,
allowing the compressor to start. Fan contactor (C13) (21] will also
close,
bringing power to the line side of fan cycling pressure
controls (FCP1) and (FCP2) (see Power Wiring Diagram- Pages 16
and 17). Fan
motor #1 will start as soon as the head pressure reaches
the "cut-in" setting of (FCP1 ).
NOTE: ALL FAN MOTORS ARE CONTROLELD BY THEIR OWN
FAN CYCLING CONTROL AND WILL CUT IN AT
DIFFERENT HEAD PRESSURES.
Relay (R19) [20] contact 7-1 [3] opens, de-energizing compressor#1
crankcase heater(s). Relay (R14) (19] contact 8-5 (24] closes,
energizing (TD7) [23]. This will force compressor #1 to run for five
minutes. COMPRESSOR #2 CANNOT BE STARTED UNTIL (TD7)
TIMES OUT.
Time delay relay (TD1 0) [63] contact C-NC (26] holds the compressor
in an unloaded condition for 30 seconds. When relay (TD10) times
out, it will energize relay (R4) [27]. closing contacts 9-6 [71] and 7-4
[74].
This allows the capacity control thermostat (T3) to energize
solenoid valve (UL 1-1) [71]. loading the compressor; or to energize
solenoid valve (UL2-1) [74]. unloading the compressor.
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Relay (R14) (19] contact 7-4 [62] closes, which completes the
interlock circuit for the water circulating pump.
~TAGE! Z LOADINu
Upon a further increase in return watertemperature, the second step
of the staging thermostat (T1) will close. If the lock-out timer (TD5)
and
the lock-in timer (TD7) [64] have timed out, relays (R2) [64] and
(TD11) [65]
will be energized, closing (R2) contacts 9-6 [32]. 8-5
[40]. and 7-4 [37]. If the safety
controls and switches are closed, the
control circuit [32] for compressor #2 and liquid line solenoid
(SOL2) [40] will energize, allowing the compressor to start.
Relay (R20) [36]
contact 7-1 [5] opens, de-energizing crankcase
heater(s). Contact 9-6 [44] closes, energizing fan contactor (C14)
(44].
bringing power to the line side of the balance of the fan cycling
pressure controls (see power wiring diagrams) . Fan motor #3 will
start
as soon as the head pressure reaches the "cut-in" setting of
(FCP3).
Relay (R16) [35]
contact 8-5 [39] closes, energizing (TD8) (38]. This
will force compressor #2 to run for five minutes. Compressor #3
cannot be started until (TDS) times out.
Time delay relay (TD11) [65] contact C-NC (41] holds compressor#2
in an unloaded condition for 30 seconds. When (TD11) times out, it
will energize (R5) (42]. closing contacts 9-6 (72] and 7-4 (75]. This
allows the capacity control thermostat (T3) to energize solenoid
valve (UL 1-2) [72]. loading the compressor; or to energize solenoid
valve (UL2-2) [75]. unloading the compressor.
STAGE 3
LOADING
Upon a further increase in return watertemperature, the third step of
the staging thermostat (T1) will close. Ifthe lock-out timer (TD6) and
the lock-in timer (TD8) (66] have timed out , relays (R3) (66]. (R7)
(68].
and (TD12) [67] will be energized. Relay (R3) contacts 9-6 [48].
7-4 [53]. and 8-5 [56] close. If
the safety controls and switches are
closed, the
control circuit [48] for compressor #3 and liquid line
solenoid (SOL3) [56] will energize, allowing the compressor to start.
Relay (R21) [52] energizes,
opening contact 7-1 [7], de-energizing
compressor #3 crankcase heater(s). Relay (R18) (51] contact 8-5
[55] closes,
energizing (TD9) [54]. This will force compressor #3 to
run
for five minutes.
Relay (R7)
contact 9-6 [70] closes, energizing solenoid valve (UL 1-
1).
thus locking compressor #1 in the fully loaded position. Relay
(R7)
contacts 8-2 [71] and 7-1 [74] open to disconnect the capacity
control thermostat (T3) from compressor #1 capacity control
solenoid valves.
Time delay relay (TD12) [67] contact C-NC [57] holds compressor
#3 in an unloaded condition for 30 seconds. When (TD12) times out ,
it
will energize relay (R6) [58]. closing contacts 9-6 [73] and 7-4 [76].
This allowsthe
capacity control thermostat (T3) to energizesolenoid
valve
(UL 1-3) [73]. loading the compressor ; or to energize solenoid
valve (UL2-3) [76].
unloading the compressor.
Compressor #1 is fully loaded.
Compressors #2 and #3 are being capacity-modulated.
7
PUMPDOWN SEQUENCE
STAGE 3 PUMPDOWN
A dccrca:>e in return water temperature will t;iiU>Se the third step or
the staging thermostat (T1) to open, thereby de-energizing staging
relay (R3),
opening contacts 8-5, 9-6, and 7-4. Liquid line solenoid
(SOL3) will de-energize, stopping the flow of refrigerant to chiller
circuit #3. The compressor will continue to run until the chiller
circuit has been cleared of refrigerant and the suction pressure is
approximately 35 PSIG. Low pressure control (LP3) contact will
then open, de-energizing compressor contactors (C5) (49] and (C6)
[50].
stopping compressor #3; and de-energizing relays (R18) and
(R21 ).Relay (R18) N.C . (normally closed) contact 2-8 (54] energizes
lock-out timer (TD6). preventing compressor #3 re-start for .five
minutes. Relay (R21) energizes
the compressor crankcase heater(s).
Staging thermostat (T1) also de-energizes relay (R7). opening
contact 9-6, releasing compressor #1 from continuous full-load
operation. Relay (R7) contacts 8-2 and 7-1 close, allowing the
capacity control thermostat (T3) to operate capacity control solenoid
valves (UL1-1) and (UL2-1)
as required.
STAGE 2
PUMPDOWN
A further decrease in return water temperature will de-energize
staging relay (R2), closing liquid line solenoid (SOL2). When chiller
circuit #2 has pumped out, low pressure control (LP2) opens,
stopping compressor #2 ; and de-energizing relays (R16) and (R20).
Relay (R16) N.C.
contact (8-2) [38] energizes lock-out timer (TD5),
preventing compressor #2 re-start for five minutes. Relay (R20) (36]
energizes
compressor#2 crankcaseheater(s); and also de-energizes
fan
contactor (C14) (44]. stopping the fan motor(s) servicing the
two-circuit condenser slab.
STAGE 1
PUMPDOWN
Step 1 of the staging thermostat (T1) will open when the return water
temperature is reduced to the set point . This de-energizes staging
relay (R1 ), closing liquid line solenoid (SOL 1), stopping refrigerant
flow to chiller circuit #1. Compressor#1 continues to run until chiller
circuit #1 pressure is down to the low pressure control (LP1) set
point. The (LP1) contact opens , de-energizing compressor contac -
tors (C1) (17]. (C2) (18], and fan contactor (C13) [21]. stopping
compressor #1 and the remaining fan motor(s).
Relay (R14) N.C. contact 8-2 (23] energizes lock-out timer (TD4),
preventing compressor #1 re-start for five minutes ; relay (R14)
contact 7-4 (62] opens, removing the circulating pump starter
interlock . Relay (R19) de-energizes, closing contacts 7-1 [3].
energizing compressor #1 crankcase heater(s).
SAFETY CONTROLS
Each refrigerant circuit is protected by seven standard safety
controls, and one optional safety control.
1. High Pressure (HP)
2.
Low Pressure Freeze (LPF)
3. High
Discharge Temperature (OTS)
4.
Low Oil Temperature (LOT)
5.
Compressor Solid State Module (CSTM)
6. Low Water Temperature (T2)
7.
Low Pressure (LP)
8.
Compressor Starter Overloads (OLH) (Optional)
If any of these devices should open due to abnormal conditions, the
compressor will automatically stop. All controls must be manually
reset, except Low Oil Temperature (LOT), Low Pressure (LP) and
Compressor Solid State Module (CSTM), which resets itself after a
two minute bleed-down period. The compressor motor windings are
also
equipped with a thermal protector, automatic reset, which is not
shown on the wiring diagram.

SEQUENCE OF OPERATION
MODEL ACWC 215 SC
The following sequence of operation is typica l for the ACWC 215 SC
(see pages 12
to 15 for typical wiring diagram ). Refer to the wiring
diagram furnished with unit for specific information.
( ) Control Identification Symbol
[ ] Circuit Line Number
Important Notel
The compressor crankcase heater must be energized and remain
active a minimum of 24 hours prior to unit start.
PRELIMINARY SEQUENCE
Place control circuit " ON-OFF " switches ( SW1 thru SW5) in the
"OFF" position , and set the staging thermostat (T1 ) to its highest
temperature.
Activate the 115 volt electrical service to terminals #2 and #4 [1 and
3] on
terminal board (TER5) to distribute power to the control circu it
up to the control ci rcuit switches. Crankcase heater relays (R20) [3],
(R21) (5], (R22)
[8], and (R23) (10] are closed and are supp lying
power to the compressor crankcase heaters. Power is also supplied
to the chiller barrel heaters (CBH1) [17] and (CBH2) [20], the
receiver heaters (RH1 , 2, 3, 4) (12, 13, 15, 16] (optional) ,and the low
ambient crankcase heaters (SCH1 , 2, 3, 4) [3, 5, 8, 10] (optional) .
Close the main power disconnect switch. Check to see that the red
indicating lights on the phase loss monitors (PLM1 ) and (PLM2) are
lit. These
lights must be on to indicate proper phase rotation for the
compressor(s). If the lights are not on, the main control circuit to the
compressors will not be energized . Reverse any two phase legs at
the main Incoming power terminal block. DO NOT reverse the leads
of the phase loss monitor , fo r this will allow the compressor to run
backwards, causing seve re damage , and WILL VOID THE
COMPRESSOR WARRANTEE!
Start-up the chilled water pump. The water flow is confirmed when
the waterflow switch completes an electrical circuit across terminals
#12 [89] and #13 [91] of terminal board (TER5). Terminals #14 [92]
and #15 (94]
provide an interlock for the water pump starter(s);
either contact (R11 ), (R12), (R13), or (R14) [95] will close any time a
compressor is running .
Set
the staging thermostat (T1) to the design range of operation (e .g.
54° F.
return water). Set the capacity contro l thermostat (T3) to the
design range of operation (e.g. 44° F. supply water).
Place
the five control circuit switches (SW1 thru SW5) in the " ON "
position , thus energizing the balance of the control circuit. The
system will
be in the "time-In" mode for five minutes before any
compressor will start.
STAGE 1 LOADING
Upon demand for cooling , the first step of the staging thermostat
(T1) will close, energizing relay (TD15) [94] and staging relay (R1)
(93],
closing (R1) contacts 7-4 [32], 8-5 [35], and 9-6 [26]. If the
safety controls and switches are closed , the control circuit [26] for
compressor #1 and liquid line solenoid (SOL 1) (35] will energize ,
allowing the compressor to start.
Relay (R20) (30]
contact 9-6 (39] closes, energizing fan contactor
(C13) (39], bringing power to the line side of fan cycling pressure
controls (FCP1) thru (FCP6) (see Power Wiring Wiring Diagram on
Pages 16 and 17). Fan motor #1 will start as soon as the head
pressure reaches
the " cut-in " setting of (FCP1 ).
NOTE: ALL FAN MOTORS ARE CONTROLLED BY THEIR OWN
FAN CYCLING CONTROL AND WILL CUT IN AT
DIFFERENT HEAD PRESSURES.
Relay (R20) contact 7-1 (3] opens, de-energizing compressor #1
crankcase heater(s). Relay (R11) [29] contact 8-5 [34] closes,
energizing (TD9) [33]. This will force compressor #1 to run for five
minutes. COMPRESSOR #3 (Stage 2) CANNOT BE STARTED
UNTIL (TD9) TIMES OUT.
Time delay relay (TD15) ]94] contact C-NC [36] holds the compressor
in an unloaded condition for 30 seconds . When relay (TD15) times
out, it will energize relay (R5) (37], closing contacts 9-6 [1 06] and 7-4
(112].
This allows the capacity control thermostat (T3) to energize
solenoid valve (UL 1-1) [1 06], loading the compressor ; or to energize
solenoid valve (UL2-1) [1 12], unloading the compressor.
Relay (R11 ) [29] contact 7-4 [95] closes, wh i ch completes the
interlock circuit for the water ci rculating pump .
STAGING 2 LOADING
Upon a further increase in return water temperature , the second step
of the staging thermostat (T1) will close. If the lock-in timer (TD9)
[95] and
lock - out timer (TD7) [95] have timed out , relays (R2) [95]
and (TD16) [96]
will beenergized, closing (R2) contacts 9-6 [62], 7-4
(67], and 8-5 [70]. If
the safety controls and switches are closed, the
control circuit [62] for compressor #3 and liquid line solenoid
(SOL3) [70] will energize , allow ing the compressorto start.
Relay (R22) [66]
contact 7-1 [8] opens , de-energizing crankcase
heater (s). Contact 9-6 [74] closes, energizing fan contactor (C14)
[74],
bringing power to the line side of fan cycling pressure controls
(FCP7) thru (FCP12) (see power wiring diagrams) . Fan motor#4 will
start as soon as the head pressure reaches the " cut-in " setting of
(FCP7).
Relay (R13) [65]
contact 8-5 [69] closes, energizing (TD11) [68].
This will fo rce compressor #3 to run for five minutes .Compressor#2
cannot be started until TD11) times out.
Time delay relay (TD16) [96] contact C-NC [71] holds compressor
#3 in an unloaded condition for 30 seconds .When (TD16) times out ,
it will energize (R7) [72], closing contacts 9-6 [1 08] and 7-4 [113].
This allows the capacity control thermostat (T3) to energize solenoid
valve (UL 1-3) [108], loading the compressor ; or to energize solenoid
valve (UL2-3) [113], unload ing the compressor.
STAGE 3 LOADING
Upon a further inc rease in return water temperature, the th ird step of
the staging thermostat (T1) will close . If lock-in timer (TD11) and
lock-out timer (TD6) [66] have timed out , relays (R3) [97], (R9) [99],
and (TD17) (98]
wil l be energized . Relay (R3) contacts 9-6 [45], 8-5
and 7-4 [50]
close . If the safety controls and switches are closed , the
control circuit [45] for compressor #2 and liquid line solenoid
(SOL2) [53] will energize , allowing the compressor to start.
Relay (R21) [49] energizes,
opening contact 7-1 [5], de-energizing
compressor #2 crankcase heater(s). Relay (R12) [48] contact 8-5
[52] closes,
energizing (TD1 0) [51]. This will force compressor#2 to
run for five minutes . Compressor #4 cannot be started until (TD10)
times out.
Relay (R9) contact 9-6 [1 05] closes, energizing solenoid valve (UL 1-
1), thus locking compressor #1 in the fully loaded position . Relay
(R9)
contacts 8-2 [106] and 7-1 [112] open to disconnect the
capacity control thermostat (T3) from compressor #1 capacity
control solenoid valves.
Time delay relay (TD17) [98] contact [54] holds compressor#2 in an
unloaded condition for 30 seconds. When (TD17) times out, it will
energize relay (R6) [55], closing contacts 9-6 [109] and 7-4 [114].
This allows the capacity control thermostat (T3) to energize solenoid
valve (UL 1·2) (1 09], loading the compressor; or to energize solenoid
valve (UL2-2) (114], unloading the compressor.
Compressor #1 is full loaded .
Compressors #2 and #3 are being capacity-modulated .
STAGE 4 LOADING
Upon a further increase in return water temperature, the fourth step
of the staging thermostat (T1) will close. If the lock-in timer (TD1 0)
and the lock-out timer (TD8) [1 00] have timed out, relays (R4) [1 00],
(R1 0) (1 02], and (TD18) [1 01] will be energized . Relay (R4) contacts
9-6 [79], 7-4 (84], and 8-5 [87] close. If the safety controls and
switches are closed , the control circuit [79] for compressor #4 and
liquid line solenoid (SOL4) [87] will energize , allowing the com pres-
sor
to start.
Relay (R23) [83] energizes,
opening contact 7-1 (7], de-energizing
compressor #4 crankcase heater(s). Relay (R14) [82] contact 8-5
(86] closes,
energizing (TD12). This will force compressor #4 to run
for five minutes .
Relay
(R1 0) contact 9-6 [1 07] closes, energizing solenoid valve
(UL1-3 , thus locking compressor #3 in the fully loaded position .
Relay
(R1 0) contacts 8-2 (1 08] and 7-1 [113] open to disconnect the
capacity control thermostat (T3) from compressor #3 capacity
8
control solenoid valves.
~
\
\....__/
~ ~

'-.._/
r
~
Time delay relay (TD18) (101] contact C-NC (88] holds compressor
#4 in an unloaded condition for30 seconds.When (TD18) times out,
it will energize relay (R8) [89]. closing contacts 9-6 [11 0) and 7:4
(116]. Thio o.llowo tho capacity control thormootat (T'l) to .. norgi:zo
solenoid valve (UL 1-4) [11 OJ, loading the compressor ; or to energize
solenoid (UL2-4) [115),
unloading the compressor .
Compressors
#1 and #3 are fully loaded.
Compressors
#2 and #4 are being capacity-modulated.
PUMPDOWN SEQUENCE
STAGE 4 PUMPDOWN
A decrease in return water temperature will cause the fourth step of
the staging
thermostat (T1) to open, thereby de-energzing staging
relay (R4),
opening contacts 8-5, 9-6, and 7-4. Liquid line solenoid
(SOL4) will de-energize,
stopping the flow of refrigerant to chiller
circuit #4. The compressor will continue to run until the chiller
circuit has been cleared of refrigerant and the suction pressure is
approximately 35 PSIG. Low pressure control (LP4) contact will
then open,
de-energizing compressorcontactors (C7) [80) and (C8)
[81),
stopping compressor #4 ; and de-energizing relays (R14) and
(R23).Relay (R14) N.C.
(normally closed) contact 2-8 [85] energizes
lock-out timer (TD8), preventing compressor #4 re-start for five
minutes. Relay (R23) energizes
compressor#4 crankcase heater(s).
Staging
thermostat (T1) also de-energizes relay (R10), opening
contact 9-6, releasing compressor #3 from continuous full-load
operation. Relay (R1 0) contacts 8-2 and 7-1 close, allowing capacity
control thermostat (T3) to operate capacity control solenoid valves
(UL1-3) and (UL2-3)
as required.
STAGE 3 PUMPDOWN
A
further decrease in return water temperature will de-energize
staging relay (R3),
closing liquid line solenoid (SOL2). When chiller
circuit #2 low-side has pumped out , low pressure control (LP2)
opens,
stopping compressor #2;and de-energizing relays (R12) and
(R21 ). Relay (R12) N.C. contact 2-9 [51) energizes lock-out timer
(TD6), preventing compressor #2 re-start for five minutes . Relay
(R21) energizes
compressor #2 crankcase heater(s).
Staging
thermostat (T1) also de-energizes relay (R9), opening
contact 9-6, releasing compressor #1 from continuous full-load
operation. Relay (R9) contacts 8-2 and 7-1 close, allowing the
capacity
control thermostat (T3) to operatecapacity control solenoid
valves
(UL 1-1) and (UL2-1) as required.
STAGE 2 PUMPDOWN
A
further decrease in return water temperature will de-energize
staging relay (R2),
closing liquid line solenoid (SOL3). When chiller
circuit #3 has pumped out, low pressure control (LP3) opens,
stopping compressor#3; and de-energizing relays (R13) and (R22).
Relay (R13) N.C.
contact 2-8 [68) energizes lock-out timer (TD7),
preventing
compressor #3 re-start for five minutes . Relay (R22)
energizes
compressor #3 crankcaseheater(s); and alsode-energizes
fan
contactor (C14) [74). stopping the fan motor(s) on the "lag" half
nf thA condAn!':Ar !':lab .
STAGE 1 PUMPDOWN
Step1
of the staging thermostat (T1) will open when the return water
temperature is reduced to the set point . This de-energizes staging
relay
(R1 ), closing liquid line solenoid (SOL 1 ), stopping refrigerant
flow to chiller circuit #1 .Compressor#1 continues to run until chiller
circuit #1 pressure is down to the low pressure control (LP1) set
point. The (LP1) contact opens, de-energizing compressor contac-
tors (C1) (27) and (C2) [28), and relay (R20), stopping compressor
#1 . Relay (R20) de-energizes fan contactor (C13), stopping the
remainingfan motor(s); and alsoenergizes compressor
#1 crankcase
heater(s).
The (LP1) contact also de-energizes relay (R11 ). Relay
(R11) N.
C. contact 2-8 [33) energizes lock-out timer (TDS), prevent-
ing
compressor #1 re-start for five minutes. Relay (R11) contact 7-4
[95) opens, removing the
circulating pump starter interlock .
SAFETY CONTROLS
Each refrigerant circuit is protected by seven standard safety
controls , and one optional safety control.
1.
High Pressure (HPO)
2. Low Pressure Freeze (LPF)
3. High Discharge Temperature (OTS)
4.
Low Oil Temperature (LOT)
5.
Compressor Solid State Module (CSTM)
6.
Low Water Temperature (T2)
7. Low Pressure (LP)
8. Compressor Starter Overloads (OLH) (optional)
If any of these devices should open due to abnormal
conditions , the compressor will automatically stop. All
controls must be manually reset, except Low Oil Temper-
ature (LOT), Low Pressure (LP) and Compressor Solid
State
Module (CSTM), which resets itself after a two
minute bleed-down period. The compressor motor wind-
ingsarealso equipped with a thermal protector, automatic
reset, which is not shown on the wiring diagram.
STAR-DELTA STARTING
OPEN TRANSITION
·The following starting sequenceappliesto the power wiring diagrams
on Page 17
as well as the control wiring on Pages 10 thru 15 . Detail
"A" on Page 10 is typical of all screw compressor star-deltastart, and
will be used as an example.
Staging relay (R1) contact 9-6 [16) closes, energizing star contactor
(S1) [168) and the 5 second transition timer (TD1) [16A). The (S1)
power contacts close, tying the center legs of the motor windings
together into the "star" (wye) configuration. The (S1) N. C. (normally
closed) auxiliary contact [18] opens to prevent contactor (C2) from
energizing. The (S1) N.O. (normally open) auxiliary contact [17)
closes,
energizing (C1) [17]. The (C1) power contacts close,
applying power to the motor .The (C1) N.O. auxiliary contact closes,
9
locking (C1) in the energized position .
The
compressor operates in the star mode until (TD1) times out (5
seconds) at
which time (TD1) contact (168) opens, de-energizing
(S1 ). The (S1) N.C. contact [18) closes, energizing contactor (C2)
[18),
closing (C2) power contacts, thereby completing the Delta
wiring configuration. (C2) N. C. auxiliary contact [16A] opens,
preventing (S1)
from energizing until the next starting sequence.
There is an instant of time (the "open transition") between the
opening of (S1) power contacts and the closing of (C2) power
contacts, in which power across the motor windings is interrupted .

0
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