10.10 Circuit Events
The following events limit operation of the circuit in some way as described in the Action Taken column. The occurrence
of a circuit event only affects the circuit on which it occurred. Circuit events are logged in the event log on the unit
controller.
10.10.1 Low Evaporator Pressure – Hold/Unload
These events are generated to indicate a temporary condition with the evaporating pressure below the hold and unload
limits
Circuit status is:
Run: Evap Press Low
The compressor does not load
anymore or even unload its capacity.
String in the Event log:
CxCmp1 LoEvapPrHold
CxCmp1 LoEvapPrUnld
Transitory condition like a fan staging
(Condenserless 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
(ethilenic or propilenic).
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.
Water temperature is low.
Increase inlet water temperature.
Check the low pressure safeties
settings.
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