WDE
45
© STULZ SpA . – all rights reserved EN/36B/08.2018
9. Troubleshooting
Problem
Possible cause
Possible solution
The controller and the
rest of the unit don’t
work
Main power supply missing
Restore power supply
Main switch (optional) open
Close main switch
DC power supply to the controller is missing
Check voltage on power supply cables. Repair the
broken cable or restore the missing connection
DC power supply not available on site (necessary
for units with DC emergency ventilation)
Install a suitable external power supply module to
transform AC into DC power supply for the DC compo-
nents (controller, fan, free cooling damper servomotor)
Controller faulty
Contact Stulz service
Controller is working,
but the rest of the unit
is not working
Faults blocking the unit
Look for alarms on the display. Contact Stulz service
Controller faulty
Contact Stulz service
Controller is working
but display is not
working
Cable between controller and display disconnect-
ed
Reconnect cable
Cable between controller and display broken
Replace cable
Display faulty
Contact Stulz service
Alarm: high / max
temperature
Cooling capacity lower than heat load
Reduce heat load or increase number of units
Bad positioning of remote temperature probe
(accessory ACTRAS)
Check and reposition probes
Wrong calibration of return air temperature probe
Check with a reference thermometer. Contact Stulz
service for calibration
Low air flow
Check and replace air filter (see also dirty filter alarm)
Insufficient cold air circulation in the site
Check unit and racks layout
Low refrigerant charge
Contact Stulz service
Compressor faulty
Look for alarms on the display. Contact Stulz service
Anomalous condensing pressure
Check condenser efficiency. Contact Stulz service
Alarm: low temperature Too cold in the room
Improve thermal insulation of the room / unit or add
external stand-alone heaters
Electric heaters faulty
Contact Stulz service
Alarm: antifreeze
Cold air recirculation
Remove obstacles near cold air supply. Verify that unit
external panels are correctly closed
Insufficient evaporator air flow
Check that evaporator fan is free to move
Wrong calibration of evaporator temperature probe Check with a reference thermometer. Contact Stulz
service for calibration
Alarm: high humidity
(if humidity probe is
present)
Humidity infiltration from outside
Check passage of air from the outdoor
Wrong calibration of humidity probe
Check with a reference hygrometer. Contact Stulz
service for calibration
Alarm: high pressure
Condenser air recirculation
Remove obstacles near the condenser air discharge.
Verify that unit external panels are correctly closed
Insufficient condenser air flow
Check that condenser fan is free to move
Clean condenser and air openings
Wrong calibration of condenser temperature probe Check with a reference thermometer.
Contact Stulz service for calibration
High pressure switch defective
Contact Stulz service
External temperature higher than max limit
Change unit model
Alarm: low pressure
Refrigerant leakages
Contact Stulz service
Low pressure switch defective
Contact Stulz service
Obstruction of refrigerant filter
Contact Stulz service
