STXC2 User’s guide
Version 2.0
19 of 30
2.7.1 Critical failure reset.
If the ventilation unit is stopped due to a critical failure, then follow these instructions:
Frost thermostat has sensed a frost condition
The frost thermostat has a manual reset. The failure is reset on the frost thermostat.
Fire thermostat has sensed a fire condition
The fire thermostat has a manual reset. The failure is reset on the fire thermostat.
Overheating thermostat - OT
The overheating thermostat mounted on the electrical heating coil and is a manual reset. The failure
is reset on the overheating thermostat.
Stopped fan motor
Switching off the mains power supply for a few minutes resets a fan failure. The mains isolator is
located on the ventilation unit.
If this doesn’t solve the problem, it is necessary for further information; this can be obtained by
opening the cover on the fan motor. Under the cover a green and a red LED indicate the fan motor
condition.
See service engineer’s guide chapter 7. Indicator lights and fault signal output for further
information.
Missing airflow
Missing airflow through the ventilation unit is reset by pressing buttons and at the same time
and hold for a few seconds.
Another possibility is turning the function switch on the ventilation unit in position OFF and then
turn it back to the desired position.
Temperature sensor failure
A temperature sensor failure appears due to a short circuit or a missing connection to the sensor.
The failure is corrected at the sensor connection or at the wiring.
Communication failure
On the MMI the text appears ”No STXC Detected”. This is due to a broken connection in the wiring
between the control circuit board STXC2 and the MMI STCU.
Heat wheel failure
See service engineer’s guide chapter 8. Finding errors on frequency converter for heat wheel for
further information.
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