Technical data

16
REPLACEMENT OF PARTS
nection cover to PCB cover, see diagram 21.
• Open cover and unclip plastic clip securing
pump cable to lower front panel.
• Pull off pump connector and earth lead.
• Undo and remove four screws securing PCB
cover to lower front panel.
• Lift off PCB cover.
• Pull off connectors CN6, CN7, CN8 and CN9 on
PCB.
• Undo and remove screw holding PCB to lower
front panel.
• Lifting PCB up slightly on LHS, pull PCB out of elec-
trical connector on ignition PCB. Leave ignition PCB
in place.
• Fit replacement PCB in reverse order to removal.
Important: When fitting replacement PCB, ensure
that control knob spindle correctly locates into PCB
adjuster slots.
• Refit connectors and covers in reverse order to
removal.
To replace ignition PCB
• Gain access to PCB's as described in previous
section.
• Remove main PCB securing screw as described
in previous section.
• Pull off three electrical connectors on PCB.
• Lift up ignition PCB, separate from main PCB and
remove from boiler.
• Fit replacement PCB in reverse order to removal.
• Refit connectors and covers in reverse order to
removal.
To replace pump
• Drain down heating circuit of boiler only as fol-
lows:
Sch 228
Hab 286
To replace microswitch assembly
• Disconnect microswitch by pulling off plug.
• Unclip external controls connector from mount-
ing bracket.
• Undo two screws securing microswitch assembly
to reversing valve assembly, see diagram 20.
• Remove microswitch assembly from reversing
valve.
• Fit replacement microswitch assembly in reverse
order to removal.
• Reconnect plug and refit external controls con-
nection to bracket.
To replace fan
• Disconnect power supply and earth leads to fan.
• Unscrew and remove two fan retaining screws
located at front edge of fan mounting plate.
• Remove fan with mounting plate attached by
pulling forwards and out of boiler.
• Unscrew and remove three screws securing fan
to fan mounting plate.
• Fit replacement fan to mounting plate and se-
cure with screws.
• Fit replacement fan to boiler in reverse order to
removal making sure that mounting plate retain-
ing lugs are properly engaged into flue hood.
• Reconnect power supply and earth leads.
Important: Make sure that fan outlet is correctly fit-
ted into the flue elbow at the top of the boiler.
Before commissioning boiler, remove the two plas-
tic transit clips from replacement fan.
To replace air pressure switch
• Locate air pressure switch in upper left hand cor-
ner of sealed chamber.
• Pull off plastic tube from left hand connection.
• Grasp pressure switch and disengage it from
bracket clips by pulling from the top.
• Remove electrical connections from switch.
• Fit electrical connections to terminals 1 and 3 of
replacement switch.
• Fit replacement switch in reverse order to re-
moval.
Important: Refit plastic tube to LEFT hand connec-
tor (marked P1).
To replace spark generator
• Locate spark generator on bracket to right hand
side of gas valve.
• Undo and remove screw securing lower termi-
nal cover to bracket and remove bracket.
• Disconnect four leads from spark generator.
• Undo and remove screw securing spark genera-
tor to bracket and remove spark generator.
• Fit replacement spark generator in reverse order
to removal.
• Reconnect two grey power supply leads and two
clear ignition leads to spark generator, the polarity
is not important.
• Refit lower terminal cover.
To replace main printed circuit board (PCB)
• With lower front panel down as described previ-
ously, undo and remove screw holding pump con-
Diagram 20
Diagram 21
SERVICING INSTRUCTIONS