Main Heating Main Heat 12, Installation & Service Manual

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Fig. 49 & Fig. 48
page 47
The fan and venturi, gas valve, injector pipe, condensate trap, fan protection sensor, spark and sensing electrodes can be accessed and changed
on the removal of the airbox door panel.
1. Remove the airbox door panel by loosening the four 1/4 turn screws ( Fig. 50 ).
15.5 Spark and Sensing Electrodes (Fig. 51 )
1. Disconnect all three leads from tabs.
Spark - Opaque cable
Earth - Green/Yellow cable
Sensing - White cable
2. Remove the two screws securing each of the electrodes to the combustion box door and remove the electrodes.
3. Fit the new electrodes (and new gasket, as required) and reassemble in reverse order.
15.6 Fan ( Fig. 52 )
WARNING: The PCB Control and Fan Assembly are 325 Vdc. Isolate at supply before access.
1. Loosen the screw holding the injector pipe into the venturi.
2. Remove the electrical connections to the fan and protection sensor on the fan.
3. Remove the wing nuts securing the fan to the base of the combustion box.
4. Lower the fan and remove.
5. If changing the fan remove the screws securing the venturi and fan protection sensor bracket, noting the positions of the injector opening and sensor
bracket, fix them to the new fan.
6. Fit the new fan and reassemble in reverse order. The injector pipe, condensate trap and gas valve can be changed after the removal of the fan.