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52 USER CONTROL PCB REPLACEMENT
Note. Fit the earth strap provided with the PCB
to your wrist and a suitable earth on the boiler
chassis.
1. Refer to Frame 41.
2. Remove the main PCB, refer to Frame 51.
3. Unclip the PCB and lift to clear the mounting
posts.
4. Fit the new PCB ensuring the 4 potentiometer
spindles line up with the control knobs which
must be in a vertical position.
5. Reassemble in reverse order.
6. Check operation of the boiler. Refer to Frames
30 & 31.
4
PCB
Control Knobs (to be in vertical position)
53 DRAINING THE BOILER
CENTRAL HEATING CIRCUIT
1. Refer to Frame 41.
2. Close all the CH water isolating valves on the
boiler inlet.
3. To drain the primary heat exchanger circuit:
Open the drain valve and attach a length of hose
to the CH drain point.
4. After replacing any component on the boiler,
remove the hose, close the drain valve and
open all system isolating valves (re-pressurise
as appropriate) before proceeding to check
operation of the boiler.
5. Check operation of the boiler. Refer to Frames
30 & 31.
Installation and Servicing
SERVICING
CH
CH
Flow
Flow
3
Potentiometer spindle
CH
CH
Circuit
CH
Circuit
CH
Gas
Gas
Drain
Retrun
Drain
Retrun
45
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