26
8.6 FAN - Fig. 28
1. Gain access behind the room sealed chamber as described in Section 8.1.
2. Remove the screw securing the air inlet pipe and remove the pipe.
3. Disconnect the fan wiring and remove the two screws securing the fan. Withdraw the fan.
4. Remove the inlet and outlet flanges from the fan. Fit them to the new fan and re-assemble in reverse order.
Ensure that the pressure tubes are connected correctly.
5. Re-assemble and test the boiler as described in Routine Servicing, Section 7.4 paragraphs 5 to 9.
8.7 IGNITION GENERATOR - Fig. 28
1. Gain access behind the front panel as described in
Section 8.1.
2. Disconnect all the wiring from the ignition generator.
3. Remove the screw securing the generator and
remove.
4. Secure the new generator in position and re-
connect the wiring.
5. Re-assemble in reverse order.
8.8 TRANSFORMER - Fig. 28
1. Gain access behind the front panel as described
in Section 8.1.
2. Remove the two screws securing the transformer
and remove the transformer.
3. Disconnect all of the wiring noting their position.
4. Fit the new transformer and re-assemble in
reverse order.
8.9 OVERHEAT THERMOSTAT - Fig. 28
1. Gain access behind the front panel as described
in Section 8.1.
2. Disconnect the wiring from the overheat thermostat.
3. Remove the two screws securing the overheat
thermostat and remove it from the flow pipe.
4. Fit the new overheat thermostat and re-assemble in reverse order.
8.10 FLUE THERMOSTAT - Fig. 28
1. Gain access behind the front panel as described in Section 8.1.
2. Position a suitable screwdriver under the thermostat retaining clip and use it to release the tension on the thermostat, then
slide the thermostat out from under the clip.
3. Disconnect the wiring.
4. Fit the new thermostat and re-assemble in reverse order.
8.11 GAS VALVE - Fig. 28
1. Gain access behind the front casing as in Section 8.1.
2. Disconnect the positive pressure tube from the gas valve.
3. Loosen the one screw securing the electrical plug and disconnect the plug.
4. Disconnect the burner manifold pipe union and the gas inlet pipe union.
5. Remove the two manifold screws from beneath the boiler and lift out the valve assembly.
6. Lift out the gas valve.
7. Fit the new assembly and re-assemble in reverse order and test for gas soundness.
8. Light the boiler. (Refer to Commissioning, Section 5.4) and the instructions supplied with the replacement valve for
adjustment of the valve.
9. Complete re-assembly as described in Routine Servicing, Section 7.4 paragraphs 5 to 9.
Alpha CD25C/28C/35C - Component Replacement
Fig. 28
Flue thermostat
Primary temperature
sensor
Overheat thermostat
Ignition electrode
Fan assembly
Ignition generator
Transformer
Gas valve
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