Circuit Rapid Stop Alarms - Daikin MICROTECH III Operating Manual

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.
Symptom
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
Reset
Local HMI
Network
Auto
47/77
Cause
Transitory condition like a fan staging
(A/C units).
Refrigerant charge is low.
Protection limit not set to fit customer
application.
High Evaporator Approach.
Water flow into water heat exchanger
is too low.
Evaporating pressure transducer is
not working properly.
EEXV is not working correctly.
It's not opening enough or it's moving
in the opposite direction.
Water temperature is low
A/C units W/C units
 
 
 
Operation Manual
Solution
Wait until the condition is recovered
by EXV control
Check sight glass on liquid line to see
if there is flash gas.
Measure sub-cooling to see if the
charge is correct.
Check the evaporator approach and
the corresponding water temperature
to evaluate the low pressure hold
limit.
Clean the evaporator
Check the quality of the fluid that
flows into heat exchanger.
Check the glycol percentage and type
(ethylenic or propylenic)
Increase the water flow.
Check that evaporator water pump is
operating correctly providing the
required water flow.
Check the sensor for proper operation
and calibrate the readings with a
gauge.
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.
Notes
D–EOMWC00A07-16_02EN