Download Main Combi 24 HE Technical data

16.0 Fault Finding
I
1.
2.
Check the gas supply pressure:
For Natural Gas greater than
10 - 11 mbar
Check and correct if necessary
1. The mechanical set of the gas valve
(CO2 values - see instruction)
2. Flame sensing electrode and lead connections
3. Flame sensing electrode position
YES
Flame current should be more than 0.5 μA
J
1.
Overheat thermostat operated or
faulty, i.e. continuity across
thermostat terminals
NO
NO
Replace PCB
Replace flame sensing electrode
Allow to cool. Continuity
across thermostat terminals
more than 1.5 ohm
YES
Replace safety thermostat
YES
Replace PCB
K
Is there 230V at:
1.
Motor 3-way valve
2.
PCB - X3 connector terminals
5 & 6 central heating mode
5 & 7 domestic hot water mode
YES
Replace motor 3-way valve
NO
Replace PCB
YES
Change pump supply cable
L
1.
M
1.
Fan connections correct at fan.
PCB - X401 connector terminals 5,6,7 & 8
Temperature sensors faulty.
Cold resistance approximately
10kΩ @ 25° C (CH sensor)
20kΩ @ 25° C (Flue sensor)
(resistance reduces with increase in temp.)
YES
NO
YES
2.
If pump is running the heat exchanger could be
obstructed
Replace fan
Replace sensor
Replace heat exchanger
51