Munters HCUw, Operating & Maintenance

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Appendix A Troubleshooting
General Possible causes
Unit will not run Carel microprocessor has an alarm (alarm button is
illuminated red). Go to 6.2 for a description of all
alarms. If there is no alarm light, check power to unit for
correct voltage on all three phases and proper phasing.
Phase protection relay will prevent unit running if
phasing is incorrect.
Refrigeration Circuits
Compressor trips on HIGH DISCHARGE
alarm Check Condenser Fan and Reactivation Fan VFDs for
trip. Check condenser coil for blockage. Ambient
temperature may be excessive (above 110F).
Compressor trips on LOW DIFF Compressor may be running backward (low discharge
pressure, high suction pressure). Airflow switch is not
adjusted properly and is shutting off compressors.
Compressor trips on LOW SUCTION
CUTOUT Compressor circuit may be low on refrigerant. Liquid
line solenoid may not be opening.
Variable Frequency Drives (VFD)
VFD trips Voltage spike may have occurred. VFD parameter
settings may be incorrect. See Appendix C for
parameter settings, fault codes, and possible solutions
for each fault.
Carel microprocessor
Display is blank Check 24V power to terminals G and G0. Check 2A
slow-blow fuse nest to G G0 terminal blocks. Remove
and reapply power to G and G0. If all else fails, re-
upload program.
Alarm light is on See 6.2 for alarm descriptions.
Carel is not receiving any analog sensor
inputs There may be a problem with the wiring causing a short-
circuit on the 21Vdc line (terminal J2, +VDC). When this
occurs, a built-in circuit breaker trips and causes a red
LED to light up between J3 and J4 (the yellow LED is
normal): Cycle power on the controller to reset the
breaker.
Cell phone modem will not communicate Cell phone is off: turn on. Cell phone is in voice mode:
power pCO2 down and back on. pCO2 SUPERVISOR
SETUP has incorrect parameters: See SUPERVISOR
SETUP in 4.4 under Service Settings. Ident number
must be correct (call factory).
Building Management System will not
communicate with pCO2 pCO2 SUPERVISOR SETUP has incorrect parameters.
See SUPERVISOR SETUP in 4.4 under Service
Settings. Each Ident must be different and matched to
the proper BMS ident number.
Desiccant wheel
Pressure drop is incorrect on process side Filter may be dirty. Supply fan speed may need
adjustment (see 4.6).
Pressure drop is incorrect on reactivation
side VFD automatically adjusts air volume to achieve correct
compressor discharge pressure. Check pressure drop
with fan running at full speed. If it is low, check filters. If
it is too high, the VFD will automatically limit the airflow
for correct reactivation temperature.
Unit trips on wheel rotation fault This alarm trips when the unit is in DH mode and the
temperature differential is less than 5ºF after 30
minutes of operation. Check to make sure wheel is
rotating.