Fault Codes on the CM737
If a spanner is visible on the display there is an on ongoing alarm. Press the Info-button to view the fault code.
No fault (power-up)
Supply water temperature sensor out of range
Outside air temperature sensor out of range
Case temperature out of range
Secondary pump or district heating supply
No OT communication
Fault code 0
This fault code can just be seen in the fault history, parameter settings category 5.
Fault code 1
Supply sensor failure
Measured supply water temperature lies below 0°C or above 100°C.
Respond with 'invalid data' when thermostat asks for supply temperature Turn the
pump off, and enter off mode.
Fault code 2
Outside sensor out of operating range. This fault code can only occur after the
measured outside temperature has been in range: -40°C to 60°C.
Measured outside temperature lies below -40°C or above 60°C
When the thermostat asks for the outside temperature the DHC will respond with
After a reset this fault code will not occur again, until a valid temperature has been
measured, and then a non-valid temperature will be measured again.
Fault code 3
Housing sensor out of operating range
Measured environment temperature lies below 0°C or above 60°C
Turn the pump off, and enter off mode
Fault code 4
Secondary pump or district heating supply:
Cannot reach the set supply water temperature
Air in the pump, low temp/ not district heating supply
Fault code 7
No OT communication:
Thermostat doesn't communicate by OT for 60 seconds
10 seconds after occurring, the DHC assumes an on/off thermostat is controller.
CH bit is cleared = 0.
Requested supply set point is cleared.
Fault is only cleared after a power cycle, OT thermostat is connected or
communication is working again.