Technical data

20
To replace expansion vessel
1 Boiler in place
Note: The expansion vessel can be replaced with
the boiler in place provided that there is a mini-
mum clearance of 400mm on one side of the boiler
and that no vertical pipework passes between
boiler and wall on that side.
• Drain down the heating circuit of the boiler only
as described in 'To replace pump'.
Note: It is not necessary to drain entire heating sys-
tem to carry out this work.
• Remove pump from boiler as described previ-
ously.
• Unscrew pipe connection nut from expansion
vessel and disengage pipe from connection. Keep
sealing washer.
• Whilst supporting weight of vessel, push bottom
of vessel away from boiler, disengaging threaded
connection from hole in rear of boiler. Allow vessel
to drop out of its two upper retaining brackets.
• Remove vessel to side of boiler.
• Fit replacement expansion vessel in reverse or-
der to removal ensuring that sealing washer is fit-
ted to vessel pipe connection.
• Check that vessel charge pressure is 1bar. Cor-
rect if necessary.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
2 Boiler removed from wall
• Drain down the heating circuit of the boiler only
as described in 'To replace pump'.
Note: It is not necessary to drain entire heating sys-
tem to carry out this work.
• Ensure that gas and electrical supplies to boiler
are turned off.
• Disconnect flue from either rear or top of boiler
as applicable.
• Disconnect external controls connections, if ap-
plicable.
• Unscrew and disconnect five connections be-
tween fixing jig and boiler.
• Disengage pipe connections. Lift boiler off hang-
ing bracket and place on a convenient working
surface.
• Remove expansion vessel from boiler as de-
scribed in previous section.
• Fit replacement vessel in reverse order to removal
and check charge pressure.
• Replace boiler on wall, tighten all connections,
gas connection first, ensuring that all sealing wash-
ers, filters and the cold water flow regulator are fit-
ted before tightening.
• Reconnect flue system.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
• Reconnect external controls connections, if ap-
plicable.
• Reconnect gas and electrical supplies to boiler.
• Check for gas soundness.
To replace boiler thermistor
• Locate boiler thermistor on heating flow pipe on
left hand side of boiler, see diagram 28.
• Unclip thermistor from pipe.
• Pull off electrical connections from thermistor.
• Fit replacement thermistor in reverse order to re-
moval.
Note: No heat sink compound is required. The po-
larity of the connections is not important.
To replace overheat thermostat
• Locate the overheat thermostat on the right
hand side of the heat exchanger.
• Pull off the electrical connections from the ther-
mostat.
• Unscrew and remove two screws holding ther-
mostat to heat exchanger.
• Fit replacement thermostat in reverse order to
removal, using heat sink compound on the con-
tact surface of thermostat.
• Refit electrical leads, the polarity is not impor-
tant.
To replace combustion chamber insulation
Front section
• Remove combustion chamber from boiler as
described in 'Routine Cleaning and Inspection'.
• Slide side panels out of combustion chamber
sides.
• Lift front insulation panel free from retaining lugs
and away from cover.
• Fit replacement panels in reverse order to re-
moval.
Rear panel
• Remove burner from boiler as described in 'Rou-
tine Cleaning and Inspection'.
• Remove clip from base of insulation panel.
• Pull bottom edge of insulation panel forward,
downward and out from behind heat exchanger.
• Fit replacement panel in reverse order to re-
moval.
• Replace burner into boiler in reverse order to re-
moval.
To replace ignition electrode
• Remove combustion chamber from boiler as
described in 'Routine Cleaning and Inspection'.
• Pull off ignition leads from ignition electrode.
• Unscrew and remove two screws holding igni-
tion electrode onto burner.
• Fit replacement ignition electrode in reverse or-
der to removal.
• Refit ignition leads, the polarity is not important.
Diagram 28
Sec 060
SERVICING INSTRUCTIONS