18.0 Fault Finding
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1.
2.
Check that the supply pressure at the test point on the gas valve is a MINIMUM of 17mbar
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 A
YES
NO
Replace PCB
Replace flame sensing electrode
J
1. | Overheat thermostat operated or | NO |
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| Allow to cool. Continuity | YES |
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| faulty, i.e. continuity across |
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| across thermostat terminals |
| Replace safety thermostat | |||||
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| thermostat terminals |
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| more than 1.5 ohm |
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| YES |
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| Replace PCB |
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K
| Is there 230V at: |
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1. |
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| Motor |
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2. |
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| PCB - X3 connector terminals |
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| 5 | & 6 central heating mode |
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| 5 | & 7 domestic hot water mode |
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YES
Change pump supply cable
Replace motor
Replace PCB
L
M
1. | Fan connections correct at fan. |
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| PCB - X401 connector terminals 5,6,7 & 8 |
1.Temperature sensors faulty. Cold resistance approximately 10kí @ 25° C (CH sensor)
20kí @ 25° C (Flue sensor)
(resistance reduces with increase in temp.)
2.If pump is running the heat exchanger could be obstructed
YES | Replace fan |
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NO
Replace sensor
YES | Replace heat exchanger |
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© Baxi Heating UK Ltd 2012 | 59 |
