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WD420/3/2007
Boilers
8.4.7
Combustion Blower (Fig. 6.7.3 item 111)
i)
ii)
iii)
iv)
v)
vi)
8.4.8
Gas Control Valve /Venturi Assembly (Fig. 6.7.3 item 183)
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
ix)
8.4.9
Flow Thermostat (Fig. 6.7.2 - 1/2 item 57)
i)
ii)
iii)
iv)
v)
8.5
SPARK IGNITION/FLAME DETECTION ELECTRODE (Fig. 6.7.2 - 1/2 item 53)
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 (Fig 6.7.2 - 1/2 item 73) and withdraw the spark ignition electrode.
v)
Reassemble (Section 8.3)
NB:
8.6
BURNER (Fig. 6.7.2 - 1/2 items 52)
i)
Isolate the appliance (Section 8.1)
ii)
Gain access (Section 8.2)
iii)
Remove the combustion blower (Section 8.4.7)
Installation & Servicing Instructions
Chapter 8 : Replacement Of Parts
Isolate the appliance (Section 8.1)
Gain access (Section 8.2)
Disconnect the connector block from the combustion blower.
Unscrew the bolts (Fig 6.7.3 item 114) securing the gas inlet pipe to the gas
control valve.
Remove the four nuts securing the combustion blower (fig. 6.7.3 item 120)
outlet flange to the burner and remove the combustion blower.
Reassemble (Section 8.3)
NB:
When reassembling inspect any gaskets for damage and replace if
necessary.
Isolate the appliance (Section 8.1)
Gain access (Section 8.2)
Remove the push on connector block to the gas valve.
Unscrew the bolts (Fig 6.7.3 item 114) securing the gas inlet pipe to the gas
control valve.
Unscrew the bolts securing the gas valve (Fig 6.7.3 item 122) to the inlet port
of the combustion blower.
Remove the gas valve/venturi assembly as a complete unit.
Unscrewing the union fitting from the gas valve.
Reassemble (Section 8.3)
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).
Isolate the appliance (Section 8.1)
Gain access (Section 8.2)
Remove the push on connector from the sensor taking note of the correct
position.
Unscrew the bolts securing the stat (Fig 6.7.2 - 1/2 item 77)
Reassemble (Section 8.3)
NB:
When fitting the new thermostat 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.
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.
The Keston Qudos 28s & Qudos 28sP
Page : 48
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