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NAC
Plug
Earth Wire
Inlet Pipe
Gas Feed
Pipe
Fig. 53
Flow Pipe
Central Heating
Temperature
Sensor
Safety
Thermostat
Fig. 54
Fig. 55
Gas Valve
DHW Temperature
Sensor
12.0 Changing Components
12.8
1. Undo the nut on the gas feed pipe under the
boiler.
2. Disconnect the two wires from the valve
modulator and the ignition lead from the NAC
plug.
3. Disconnect the earth wire from the NAC plug
and spade terminal on the gas valve body.
4. Undo the screw securing the NAC plug to the
gas valve. Carefully pull the NAC forwards off the
valve.
5. Remove the screws securing the inlet pipe
flange to the boiler bottom panel and the screws
securing the valve outlet manifold to the manifold
inlet elbow.
6. Remove the valve from the boiler.
7. Note the orientation of the inlet pipe and outlet
manifold. Undo the securing screws and remove
the pipe and manifold.
8. Examine the 'O' ring seals for damage,
replacing as necessary.
9. Fit the inlet pipe and outlet manifold to the new
valve, ensuring that the 'O' ring seals are in place.
10. Reassemble in reverse order and check the
pressure as described in Section 9.2.
12.9
1. Ease the retaining tab on the sensor away and
disconnect the electrical plug.
2. Unscrew the sensor from it's pocket and
reassemble in reverse order. The plug will only fit
one way.
12.10
1. Pull the two electrical connections off the
thermostat.
2. Remove the screws securing the thermostat to
the mounting plate on the flow pipe.
3. Reassemble in reverse order. The thermostat is
not polarised - either wire can fit either terminal on
the thermostat.
12.11
1. Turn off the mains water supply and draw off
the residual domestic hot water.
2. Ease the retaining tab on the sensor away and
disconnect the electrical plug.
3. Unscrew the sensor from the plate heat
Plate Heat
exchanger manifold. Examine the sealing washer,
Exchanger
replacing if necessary.
4. Reassemble in reverse order. The plug will only
fit one way.
Gas Valve (Fig. 53)
Central Heating Temperature Sensor
(Fig. 54)
Safety Thermostat
(Fig. 54)
DHW Temperature Sensor
(Fig. 55)
31
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