7.4.8
Gas Control Valve / Venturi Assembly (Fig. 5.7.3 item 163)
i)
Isolate the appliance (Section 7.1)
ii)
Gain access (Section 7.2)
iii)
Remove the push on connector block to the gas valve.
iv)
Unscrew the bolts (Fig 6.7.3 item 149) securing the gas inlet pipe to the
gas control valve / venturi assembly.
v)
Unscrew the bolts securing the gas control valve / venturi assembly (Fig
6.7.3 item 81) to the inlet port of the combustion blower.
vi)
Remove the gas valve/venturi assembly as a complete unit.
vii)
Reassemble (Section 7.3)
viii)
Check the gas rate and combustion (See Section 4 - 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 4.7 (Combustion testing).
7.5
SPARK IGNITION/FLAME DETECTION ELECTRODE (Fig. 5.7.2 item 74)
i)
Isolate the appliance (Section 7.1)
ii)
Gain access (Section 7.2)
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 side panel and withdraw the spark ignition electrode.
v)
Reassemble (Section 7.3)
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 earth post is 3 mm.
Distances above or below 3 mm will affect ignition performance. If
necessary gently bend the electrode taking care not to damage the
ceramic insulator.
7.6
BURNER (Fig. 5.7.2 items 77)
i)
Isolate the appliance (Section 7.1)
ii)
Gain access (Section 7.2)
iii)
Remove the combustion blower (Section 7.4.7)
iv)
Remove the 12 nuts fixing the burner to the top of the heat exchanger.
v)
Withdraw the burner from the top of the heat exchanger.
vi)
Reassemble (Section 7.3)
NB:
When reassembling inspect any gaskets for damage and replace if
necessary.
7.7
HEAT EXCHANGER (Fig. 5.7.2 item 36)
i)
Isolate the appliance (Section 7.1)
ii)
Gain access (Section 7.2)
iii)
Shut of the water supply to the appliance.
iv)
Remove the burner (Section 7.6)
v)
Drain the system to below the level of the appliance using the drain off tap at the
base of the boiler return pipe.
vi)
Remove the flue protection thermostat (Section 7.4.4)
vii)
Remove the spark ignition/flame detection electrode (Section 7.5)
viii)
Remove the flue connection by slackening the retaining strap and pulling the flue
off the heat exchanger spigot.
ix)
Remove the condensate trap hose (Fig 5.7.2 item 54) by releasing the retaining
clamp and pulling the hose away from the spigot at the base of the heat
exchanger flue outlet box.
x)
Disconnect the flow and return pipe unions (Fig 5.7.2 item 45) from the heat
exchanger.
WD536 Chapter 7 : Replacement Of Parts
The Keston C45, C40P, C55 & C55P
Installation & Servicing Instructions
Page : 43