17
Mynute
Fig. 20
6.7
AUTOMATIC AIR RELEASE VALVE
(see fig. 18) (AAV)
Carry out component removal procedure as de-
scribed in 6.4.
Using a suitable pair of pump pliers, unscrew the
AAV from pump base.
Replace in the reverse order.
6.8
WATER PRESSURE SWITCH (see fig. 19)
Carry out component removal procedure as
described in 6.4.
Remove locking screw and the water pressure
switch from the heating manifold, and - after
taking note of the electrical connections -
disconnect the wiring.
Replace in the reverse order.
6.9
PRESSURE GAUGE (see fig. 19)
Carry out component removal procedure as de-
scribed in 6.4.
Remove pressure gauge locking screw, located
on pump base, and withdraw the pressure gauge
pipe, locate the spring tabs on the pressure
gauge body, push and hold tabs in, to enable
extraction of the gauge from its location.
Replace in the reverse order.
6.10
NTC THERMISTORS (see fig. 20)
Carry out component removal procedure as de-
scribed in 6.4.
Unclip and remove the air chamber cover, and
remove the right side air baffle. Disconnect
thermistor electrical plug. Using a 13mm spanner
slacken and remove the thermistor and sealing
washer.
Replace in the reverse order.
6.11
HIGH LIMIT THERMOSTAT (see fig. 20)
Carry out component removal procedure as de-
scribed in 6.4.
Unclip and remove the air chamber cover. Pull of
electrical connections from the high limit
thermostat, slacken and remove retaining screws.
Replace in the reverse order.
6.12
PRINTED CIRCUIT BOARD (PCB)
Carry out component removal procedure as de-
scribed in 6.4. Located and remove the five
screws which secure the PCB cover & terminal
cover, then remove cover, after carefully taking
note of all wiring connections, disconnect all
wiring from the PCB, locate and remove the PCB
securing screws, remove PCB.
Replace in the reverse order.
NOTE
Ensure that the replacement PCB has the correct
“Jumper Tag” configuration (see section 8).
6.13
GAS VALVE (see fig. 21)
Carry out component removal procedure as de-
scribed in 6.4.
The gas valve must be changed as complete unit.
Disconnect the electrical plug and leads from the
gas valve. Disconnect compensator tube from
gas valve regulator. Slacken and unscrew gas
valve inlet and outlet connections. Please note,
the sealing washers must be discarded and re-
placed with new sealing washers. Locate and
remove gas valve retaining screws on the
underside of the boiler if required, the gas valve
can now be removed. Replace in the reverse
order. Check and adjust burner pressure settings.
WARNING, A GAS SOUNDNESS CHECK
MUST BE CARRIED OUT.
6.14
INTEGRAL TIME SWITCH (if fitted)
Carry out component removal procedure as de-
scribed in 6.4.
Locate and remove the terminal cover and
securing screws (2), locate and remove the time
clock retaining screws, remove time clock.
Disconnect wiring after carefully taking note of
alla electrical connections.
Replace in the reverse order.
6.15
BURNER, INJECTORS AND SPARK/SENSE
ELECTRODE (see fig. 22)
Carry out component removal procedure as de-
scribed in 6.4.
Unclip and remove the air chamber cover.
Locate and remove the screws securing the front
combustion cover, pull the cover towards you
before lifting and disengaging.
Fig. 21
1 Outlet pipe
2 Fibre washer
3 Gas valve
4 Retaining screws
5 Inlet pipe
6 Compensator tube
(only for 28e)
1
2
3
4
5
1 Heat exchanger
2 Aluminium washer
3 NTC thermistor
4 High-limit thermostat
5 Retaining screws
1
2
3
2
4
5
6