v)
Unscrew the bolts (Fig 6.7.3 - item 99 & 100) securing the gas inlet pipe to
the gas control valve.
vi)
Unscrew the bolts securing the gas valve (Fig 6.7.3 - item 95) 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 Chapter 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).
8.5
SPARK IGNITION/FLAME DETECTION ELECTRODE (Fig. 6.7.2 - item 54)
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 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.
8.6
BURNER (Fig. 6.7.2 - items 52)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Remove the combustion blower (Section 8.4.7)
iv)
Remove the four nuts fixing the burner to the top of the heat exchanger (Fig. 6.7.3 -
item 93).
v)
Withdraw the burner from the top of the heat exchanger.
vi)
Reassemble (Section 8.3)
NB:
When reassembling inspect any gaskets for damage and replace if
necessary.
8.7
HEAT EXCHANGER (Fig. 6.7.2 - item 51)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Shut off the water supply to the appliance.
iv)
Remove the burner (Section 8.6)
v)
Drain the system to below the level of the appliance using the drain off tap (Fig.
6.7.4 - item 66) at the base of the boiler return pipe.
vi)
Remove the flue thermistor (Section 8.4.4)
vii)
Remove the spark ignition/flame detection electrode (Section 8.5)
viii)
Remove the four screws (Fig. 6.7.4 - item 16) fixing the flue connection.
ix)
Remove the condensate trap hose (Fig 6.7.2 - item 77) by releasing the retaining
clamp and pulling the hose away from the spigot at the base of the heat exchanger.
x)
Disconnect the flow and return pipe union nuts (Fig 6.7.2 - item 59 & 64) from the heat
exchanger.
xi)
Remove the three screws (Fig. 6.7.2 - item 79) fixing the heat exchanger to the top
(two screws) and the bottom (one screw).
xii)
Remove the heat exchanger
xiii)
Reassemble (Section 8.3)
xiv)
Recommission (Section 5 - Commissioning)
8.8
CONDENSATE TRAP (Fig. 6.7.2 - item 73)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Disconnect the condensate line from the base of the heat exchanger.
WD500
Chapter 8 : Replacement Of Parts The Keston Q37 & Q37P Boilers
Installation & Servicing Instructions
Page : 46
