Gulf+Western ACWC-SC - Low Ambient Operation; Control Settings; Unit Operating Limitations

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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 PSI G.
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).
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