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4.0 ELECTRICAL
4.3.6.8 Liquid Line Solenoid Control
When compressors starts, the liquid
line solenoid will energize when suction
pressure falls below the pumpout
setpoint or a time delay of 5 seconds is
elapsed. For unit with two liquid lines
per refrigerant circuit, the second liquid
line solenoid will energize when suction
pressure falls below low pressure
cutout setpoint or a time delay of 25
seconds is elapsed and unit target is
above 40%. The second liquid line
solenoid will be de-energized when the
unit target is less than 35%.
4.3.6.9 Sump Heater Control
Each compressor is fitted with an oil
sump band-heater. The heater is
energized at all times when compressor
is off and de-energized when the
compressor is running.
Its purpose is to prevent refrigerant
migration into the oil during shut down.
For this reason, it is essential that
heaters be energized for 24 hours
before starting a compressor.
4.3.6.10 Low Pressure Cut-off
This function protects the unit from
operating at abnormally low evaporator
refrigerant pressure. The controller will
shut down the compressor when
evaporator pressure falls below the low
pressure setpoint and turn on the alarm
pilot light.
A low pressure alarm will be recorded
by the controller. Reset by pressing the
‘Reset Alarm’ button on the controller.
Standard setpoint is 58 psig [4.0BAR].
4.3.6.11 Evaporator Freeze Shutoff
If the leaving chilled water temperature
drops below the freeze setpoint, the
controller will shut down the unit and
store the freeze alarm. After solving the
problem, press ‘Reset Alarm’ on the
controller to clear the alarm.
4.3.6.12 High Pressure Cut-off
This function protects the compressor
from operating at abnormally high
discharge refrigerant pressures. The
controller will shut down the
compressor when condenser pressure
reaches the high pressure set point,
and turn on the alarm indicator lamp on
the control box. The high discharge
pressure alarm will be recorded by the
controller. Reset by pressing the ‘Reset
Alarm’ button on the controller. Setpoint
is 400 psig [27.6BAR].
4.3.6.13 Phase Control Relay (PCR)
- Optional
The PCR protects the unit from the
following electric supply malfunctions:
Undervoltage, phase reversal and
single phasing. If the PCR trips, a
control relay (lCR) will de-energize and
open the control circuit. A green LED
indicates presence of power supply.
The yellow LED indicates a good
voltage supply. The power loss setpoint
is factory set to AUTO to allow
automatic start after PCR failure.
Compressor will not start for 15 minutes
after failure. To select manual reset, set
power loss setpoint to MANUAL. In this
case, a power loss alarm will be stored
by the controller and ‘Reset Alarm’
must be pressed to start.
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