8.10
THERMISTOR
The thermistor is clipped to the flow pipe below the overheat
thermostat.
The thermistor does not penetrate the waterways, therefore
it is not necessary to drain the appliance.
– Remove the casing front panel as described in section 5.1.
– Remove the thermistor securing clip from the pipe.
– Pull off the thermistor connection plug, and release the
thermistor from the clip.
– Replace the thermistor and re-assemble in reverse order
using the heat sink compound supplied.
8.11
IGNITION CONTROL BOX
– Remove the casing front panel as described in section 5.1.
– Unscrew the single screw securing the plastic ignition con-
trol box to the gas valve and pull off the control box in a for-
wards direction.
– Unscrew the single screw securing the plastic control box
cover to reveal the electrical connections.
– Transfer the electrical connectors and wires etc to the
new PCB and re-assemble in reverse order.
8.12
DRIVER PCB
– Remove the casing front panel as described in section 5.1.
– Pivot the control box downwards, by removing the two
screws.
– Open the plastic driver control box housing by removing the
room thermostat cover (one screw) and the single central
fixing screw then prising open the four locating tabs.
– Pull off the potentiometer knobs.
– Release the PCB (four screws), transfer all connections
onto the new PCB, and re-assemble in reverse order.
– Re-set the CH burner pressure as described in section 4.3.
8.13
PUMP
– Remove the casing front panel as described in section 5.1.
– Unplug the electrical connection plug.
– Isolate the C.H. flow and return valves (17 - 18 fig. 2), and
drain the appliance through the drain plug (13 fig 2).
– Unscrew both union connections.
– Replace the pump, and re-assemble in reverse order, using
the new gaskets supplied with the pump. If the new pump
is fitted with a speed adjuster, ensure that the speed is set
to maximum.
– Refill and commission the system as described in section 4.1.
8.14
D.H.W. HEAT EXCHANGER
– Remove the casing front panel as described in section 5.1.
– Remove the gas valve (to improve access) as described in
section 8.6.
– Isolate the C.H. flow and return valves, and the D.H.W. iso-
lation valve (17 - 18 - 19 fig. 2).
– Drain the appliance through the drain plug (13 fig 2).
– Drain the D.H.W. circuit by opening any D.H.W. tap below
the level of the boiler.
– Remove the two screws pivot the control box downwards.
– Disconnect all union connections to the D.H.W. heat
exchanger and remove the heat exchanger.
– Fit new heat exchanger and re-assemble in reverse order
using the new gaskets supplied with the heat exchanger.
– Refill and re-commission the system as described in section 4.1.
8.15
DIVERTOR VALVE - COMPLETE
– Remove the casing front panel as described in section 5.1.
– Remove the gas valve (to improve access) as described in
section 8.6.
– Isolate the C.H. flow and return valves, and the D.H.W. iso-
lation valve (17 - 18 - 19 fig. 2).
– Drain the appliance through the drain plug (13 fig 2)
– Drain the D.H.W. circuit by opening any D.H.W. tap below
the level of the boiler.
– Remove the two screws pivot the control box downwards.
– Disconnect all union connections from the divertor valve.
Withdraw the valve and remove the circlip securing the
microswitch assembly.
– Transfer the electrical connections onto the new valve. If
necessary. refer to the wiring diagrams in section 7.
– Re-assemble in reverse order, using the new gaskets sup-
plied with the valve.
– Refill and re-commission the system as described in section 4.1.
8.16
DIVERTOR VALVE - MICROSWITCH
ASSEMBLY
– Remove the casing front panel as described in section 5.1.
– Remove the two screws pivot the control box downwards.
– Pull out the microswitch circlip, and lift off the microswitch
assembly.
– Transfer the electrical connections onto the new
microswitch assembly. If necessary. refer to the wiring dia-
grams in section 7.
– Re-assemble in reverse order.
8.17
C.H. EXPANSION VESSEL
In the unlikely event of failure of the expansion vessel
diaphragm it is acceptable to leave the vessel in position and to
fit a replacement vessel (of similar or greater capacity) exter-
nal to the appliance but as close as possible to the C.H. return.
Alternatively the vessel can be replaced as follows. Note
replacement is not recommended if a rear flue outlet is used
or if the clearance above the casing is less than 300 mm.
– Remove the casing front panel as described in section 5.1.
– Isolate the C.H. flow and return valves (17 - 18 fig. 2), and
drain the appliance through the drain plug (13 fig. 2).
– Unscrew the expansion vessel pipe union at its connec-
24
Temperature (°C)
Resistance (
Ω
)
20
12,764
30
8,579
35
7,102
40
5,915
45
4,955
50
4,173
55
3,533
60
3,006
70
2,208
80
1,650
TABLE 9