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
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