18
?
Disconnect electrical connections to gas valve
modulating coil.
?
Undo main gas supply tube nut from gas valve,
see diagram 43.
Note :
The washer must be kept for use on
reassembly.
?
Undo main gas connection nut between gas
valve supply tube and gas inlet valve.
Note :
The washer must be kept for use on
reassembly.
?
Remove the two fitting screw and washers of
gas valve from the bottom side of boiler.
?
Withdraw gas valve assembly.
?
Using the old gas valve as a guide, transfer old
connections to replacement gas valve.
?
Refit electrical connections in reverse order to
removal, the polarity of the wires to the modulating
coil is not important. See diagram 11.
5.11. To replace central heating safety valve
If safety valve seating is damaged, it will be
necessary to replace safety valve as a complete
unit, repair is not possible.
?
Drain down heating circuit of boiler only, as
described previously.
?
Disconnect discharge pipe from safety valve.
?
To reach the valve easier, remove the right side
panel as shown in diagram 7.
?
Remove safety valve, see diagram 45.
?
Fit replacement safety valve in reverse order to
removal.
Note :
The washer must not be forgotten for use on
reassembly.
5.12. To replace heat exchanger
?
Drain down heating circuit of boiler only, as
described previously.
Note :
It is not necessary to drain down entire
heating system to carry out this work.
?
Replace the heat exchanger as described in
‘Routine Cleaning and Inspection’
Note :
The washer must not be forgotten for use on
reassembly.
?
Open isolating valves on flow and return
connections; refill, vent and pressurise boiler.
Diagram 42
Diagram 43
Diagram 44
Diagram 45