10.8 Circuit Rapid Stop Alarms
10.8.1 Low Evaporator Pressure
This alarm is generated in case the evaporating pressure drops below the Low Pressure Unload and the control is not
able to compensate to this condition.
Circuit status is Off.
The compressor does not load
anymore or even unload, circuit is
stopped immediately.
Bell icon is moving on controller’s
display. String in the alarm list:
CxCmp1 OffEvpPressLo
String in the alarm log:
CxCmp1 OffEvpPressLo
String in the alarm snapshot
CxCmp1 OffEvpPressLo
Transitory condition like a fan staging
(A/C units).
Wait until the condition is recovered
by EXV control
Refrigerant charge is low.
Check sight glass on liquid line to see
if there is flash gas.
Measure sub-cooling to see if the
charge is correct.
Protection limit not set to fit customer
application.
Check the evaporator approach and
the corresponding water temperature
to evaluate the low pressure hold
limit.
High Evaporator Approach.
Check the quality of the fluid that
flows into heat exchanger.
Check the glycol percentage and type
(ethylenic or propylenic)
Water flow into water heat exchanger
is too low.
Check that evaporator water pump is
operating correctly providing the
required water flow.
Evaporating pressure transducer is
not working properly.
Check the sensor for proper operation
and calibrate the readings with a
gauge.
EEXV is not working correctly.
It’s not opening enough or it’s moving
in the opposite direction.
Check if pump-down can be finished
for pressure limit reached;
Check expansion valve movements.
Check connection to the valve driver
on the wiring diagram.
Measure the resistance of each
winding, it has to be different from 0
Ohm.
Increase inlet water temperature.
Check the low pressure safeties
settings.
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