NB:
When reassembling inspect any gaskets for damage and replace if
necessary.
8.4.8
Gas Control Valve /Venturi Assembly
(Fig. 6.7.3 item 215)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Remove the Main Control Box (Section 8.4.6)
iv)
Remove the push on connector block to the gas valve.
v)
Unscrew the bolts (Fig 6.7.3 item 129) securing the gas inlet pipe to the gas
control valve.
vi)
Unscrew the bolts securing the gas valve (Fig 6.7.3 item 125) to the inlet port
of the combustion blower.
vii)
Remove the gas valve/venturi assembly as a complete unit.
viii)
Reassemble (Section 8.3)
ix)
Check the gas rate and combustion(See Section 5 - Commissioning)
NB:
Always change the gas valve/venturi assembly together. This
assembly is factory preset but must be checked using the procedure
set out in Section 5.7 (Combustion testing).
8.4.9
DHW Thermistor
(Fig. 6.7.2 - 2/3 item 108)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Remove the push on connectors from the thermistor taking note of the correct
positions.
iv)
Unclip the thermistor from the pipe.
v)
Reassemble (Section 8.3)
NB:
When fitting the new thermistor it is an advantage to smear a thin film
of heat sink compound between the thermistor and pipe. This,
combined with fitting the new thermistor tightly to the pipe, ensures a
good contact.
8.4.10 Flow Sensor
(Fig. 6.7.2 - 3/3 item 94)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Shut off the water supply (CWS) to the DHW heat exchanger (Fig. 6.7.2 -
1/3 item 57).
iv)
Remove the push on connector from the sensor taking note of the correct
position.
v)
Disconnect the union nuts (Fig. 6.7.2 - 3/3 item 100 and Fig. 6.7.4 - 2/2 item
177) and the fixing nut (Fig. 6.7.2 - 3/3 item 203) from the sensor.
vi)
Reassemble (Section 8.3)
NB:
When reassembling inspect the gaskets for damage and replace
if necessary.
8.5
SPARK IGNITION/FLAME DETECTION ELECTRODE
(Fig. 6.7.2 - 1/3 item 48)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Remove the pull off HT lead to the spark ignition electrode.
iv)
Undo the screws to the spark ignition electrode flange located on the heat exchanger
top panel and withdraw the spark ignition electrode.
v)
Reassemble (Section 8.3)
NB:
When reassembling inspect the gasket for damage and replace if necessary.
With the new spark ignition electrode in place it is essential to ensure the gap
between the tip of the electrode and the burner surface is 4 mm. Distances
above or below 4 mm will affect ignition performance. If necessary gently
bend the electrode taking care not to damage the ceramic insulator.
8.6
BURNER
(Fig. 6.7.2 - 1/3 items 46)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
WD388/0/2004 Chapter 8 : Replacement Of Parts The Keston C36 Combi & C36P Combi Boilers
Boilers
Installation & Servicing Instructions
Page : 44
