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10.2 Other faults
10.2.1 No heat (central heating)
10.2.2 Central heating does not reach the correct temperature
10.2.3 Central heating system remains too warm
Possible causes Analysis Solution
The power LED is not illuminated. Yes
↓ No
Check the power supply.
Check the fuse; see Electrical schematic §12.1.
The right display shows a line (
––).
The boiler is o.
Yes
↓ No
Switch on the boiler by touching just above the power LED and
holding this for 2 seconds
Room thermostat / weather-
dependent control is not connected
or is defective.
Yes
↓ No
Check the wiring.
Check OpenTherm, On/O connection of the boiler, or the
connection between the central heating boiler and the
OpenTherm room thermostat. Replace the thermostat.
Replace the weather-dependent control.
No electricity (24V). Yes Replace defective programmer. Check the wiring according to
the schematic.
Check Connector X13.
Possible causes Analysis Solution
System water pressure is too low. Yes
↓ No
Top up the system via the filling loop; see §8.2.1.
Room thermostat is turned down.
Yes
↓ No
Check the setting and adjust it if necessary.
Temperature is set too low. Yes
↓ No
Increase the central heating temperature; see central heating
demand. If an outdoor sensor is present: check the sensor
location or for damage, check curve setting (see §9.7)
Poor or no flow in the system. Yes
↓ No
Check the t (±20°C) between central heating flow and return.
Ensure no air locks are in system also check pump speed
setting parameter P031, P032.
The boiler output is not correctly set. Yes
↓ No
Adjust the boiler capacity. See §9.5 and §9.6.
No heat transfer due to debris within
the central heating boiler/system.
Yes
↓ No
Flush and clean the heating system via the central heating
circuit to BS 7593 and install a return magnetic filter.
Flue and/or air supply duct is blocked
or restricted.
Yes Check and (if necessary) clean the flue and the air supply duct.
Possible causes Analysis Solution
Room thermostat / weather-
dependent control is defective or has
a short circuit.
Yes
↓ No
Check the wiring or batteries if applicable.
Check OpenTherm, On/O connection of the boiler, or the
connection between the central heating boiler and the RF room
thermostat. Replace the thermostat.
Replace the weather-dependent control.
There is thermo-syphon in the
central heating circuit (Radiators
getting warm when DHW operates
with combination boilers).
Yes
For thermo-syphon Install a check valve in the CH return
pipework near the boiler. For under floor heating install a
"normally open" zone valve into the flow circuit. (see under
floor wiring diagram on our website).
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