Publication No. 5105703
30 To Service the Boiler & Component Replacement
4.16
Overheat Thermostat
4. Remove door by undoing the two lower fixing screws
and lifting door off the two upper hinge brackets.
5. Disconnect the two push on electrical connections
from the overheat thermostat terminals.
6. Remove the nut securing the overheat thermostat to
its mounting bracket.
7. Noting the route taken by the capillary, loosen the
plastic screw retaining the thermostat bulb and
withdraw bulb from its pocket. Remove the split
grommet in the base of the boiler, feed the thermostat
capillary and bulb through the hole.
8. Replacement is the reverse of removal. Ensure the
rubber grommet in the base of the boiler makes a
good seal around the capillary. Ensure that the
capillary is secure in the clips provided. Refer to Fig.
21.
9. Follow the full commissioning procedure as detailed
in the Commissioning section of these instructions
on page 21.
4.17
Boiler Thermostat
4. Remove door by undoing the two lower fixing screws
and lifting door off the two upper hinge brackets.
5. Disconnect the fan supply leads from the connector
adjacent to the fan.
6. Remove the screws securing the fan mounting plate,
leaving in place the three screws circled red (or with
adjacent 'F' mark), and remove the plate complete
with fan.
7. Disconnect the electrical connections as follows:-
White from terminal C(3). White from NC(2) - Refer to
Figs. 27 & 28.
8. Pull off the outer thermostat knob.
9. Remove inner thermostat post by undoing the two
securing screws.
10.Remove the nut securing the thermostat to the
control box.
11.If the boiler is fitted with a left hand flue, remove the
flue elbow as described in Section 4.1, Preparing the
Boiler for Servicing, operations F & G.
12.Remove the clip securing the thermostat bulb to the
flow pipe.
13.Remove the split grommet in the base of the boiler
and the split grommet in the fan chamber. Feed the
capillary and bulb through the holes.
14.Replacement is the reverse of removal. The bulb of
the new thermostat should be coated with heat
conducting paste. Ensure the rubber grommets in
the base of the boiler and the fan chamber make a
good seal around the capillary.
15.Ensure that the capillary is secure in the clips
provided.
Follow the full commissioning procedure as
detailed in the Commissioning section of these
instructions on page 21.
4.18
Gravity Hot Water/Pump Overrun Thermostat
4. Remove door by undoing the lower fixing screws and
lifting door off the two upper hinge brackets.
5. Disconnect the electrical connections as follows:
2 red wires from terminal NO (4)
2 brown wires from terminal NC (2)
1 white and 1 blue wire from terminal C (3)
(These are the larger numbers marked on the
thermostat, ignore the smaller numbers).
6. Remove the screws securing the thermostat to the
control box.
7. Remove the split pin retaining the thermostat bulb in
the pocket and withdraw the bulb.
8. Remove the split grommet in the base of the boiler.
Feed the capillary and bulb through the hole.
9. Replacement is the reverse of removal. The bulb of
the new thermostat should be coated with heat
conducting paste. Ensure the rubber grommet makes
a good seal around the capillary.
10.Ensure that the capillary is secure in the clips
provided. Follow the full commissioning procedure
as detailed in the Commissioning section of these
instructions on page 21.
4.19
Heat Exchanger Pipe Seal
4. Remove door and fan mounting plate as described in
4.17, sections 4, 5 & 6.
5. Loosen pipe nut, lift pipe and remove seal.
6. The return pipe is marked with an indentation, this
should face towards the front of the boiler.