Main Combi 24 HE Manuel de service télécharger pdf (Page 51)

51

16.0 Fault Finding

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

Flame current should be more than 0.5 μA

Replace PCB

Replace PCB

YES

YES

Replace flame sensing electrode

NO

Check the gas supply pressure:

For Natural Gas greater than

10 - 11 mbar

I

K

Replace safety thermostat

YES

NO

Overheat thermostat operated or

faulty, i.e. continuity across

thermostat terminals

Allow to cool. Continuity

across thermostat terminals

more than 1.5 ohm

J

L

M

Is there 230V at:

Motor 3-way valve Replace motor 3-way valve

1.

YES

PCB - X3 connector terminals

5 & 6 central heating mode

5 & 7 domestic hot water mode

Replace PCB

2.

NO

Change pump supply cable

YES

Fan connections correct at fan.

PCB - X401 connector terminals 5,6,7 & 8

1.

YES

Replace fan

Temperature sensors faulty.

Cold resistance approximately

10kΩ @ 25° C (CH sensor)

20kΩ @ 25° C (Flue sensor)

(resistance reduces with increase in temp.)

NO

Replace sensor

YES

If pump is running the heat exchanger could be

obstructed

Replace heat exchanger

1.

2.

1.

2.

1.

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