SERVICING AND SPARES
6 720 815 724 (2015/11) 41
Fig. 68
3. Remove the burner (H) and clean components.
Do not use a wire brush.
Fig. 69
6.1.6 To Check the Diaphragm in Burner Cover
4. Carefully withdraw diaphragm (J) from fan intake tube and check for
soiling and splits.
▶ Carefully refit diaphragm (J) the correct way round into the fan intake
tube.
▶ Re-assemble the burner in the reverse order using a new seal (K).
▶ Adjust air/gas ratio. Refer to section 6.2 “Setting the air/gas ratio”.
6.1.7 To Clean the Siphon/Condensate Trap
1. Pull condensate hose out of the trap.
2. Remove trap from boiler.
▶ Clean the trap and check that the connection to the heat exchanger is
clear.
▶ Fill the condensate trap with approximately 250 millilitres of water
and refit in reverse order.
Fig. 70 Siphon removal
6.2 Setting the air/gas ratio
Setting the CO
2
1. Connect manometer to inlet test point on the gas valve.
▶ To adjust the CO
2
it will be necessary to first operate the boiler at
maximum output.
▶ Press and hold down the performance test button for 10 seconds
until illuminated.
2. Turn central heating control to maximum; the boiler will then go to
maximum output.
3. Using a flat blade screwdriver set the CO
2
via the max adjuster
referring to the table below.
F
C
D
2.
6 720 812 175-16.1O
H
G
EE
3.
6 720 812 175-17.1O
J
I
K
4.
6720647361-66.1Wo
NOTICE: Air/Gas ratio
▶ The setting of the gas ratio must be carried out by a
competent person.
Setting the air/gas ratio must not be attempted
unless the person carrying out the operation is
equipped with a combustion analyser conforming to
BS 7927 and is competent in its use.
When fitted with the optional diverter valve (not
supplied) and running in performance test mode, the
boiler will only operate the central heating circuits.
If fitted to an S or Y plan system, the system must only be
run in central heating mode.
This is to allow sufficient time for this part of the
commissioning procedure.
The control will resume normal operation after 15
minutes or if the performance test button is pressed for
over a second.
CO
2
should be measured 10 minutes after firing the
appliance.
6 720 815 724-13.1O
2.
1.
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