37
6 REPLACEMENT OF PARTS
6.1 EXPANSION VESSEL
– Turn off power supply
– Remove boiler cover, see 4.4.
– Isolate flow and return valves
– Drain boiler using fitted drain vent
– Disconnect expansion pipe
– Loosen top fixing screw and remove
lower expansion vessel locking nut.
– Remove vessel and transfer the fixing
bracket to the new vessel.
– Check new vessel for correct pressu-
re 1- 1.25 bar
– Refit in reverse order.
6.2 IGNITION ELECTRODE
– Turn off power supply
– Remove boiler cover see 4.4
– Remove sealed chamber cover
– Disconnect electrode from ignition
transformer
– Pull lead through grommet
– Remove electrode fixing screw
– Carefully remove electrode from bur-
ner
– Replace in reverse order.
6.3 IONISATION ELECTRODE
– Turn off power supply
– Remove boiler cover see 4.4
– Remove sealed chamber cover
– Disconnect electrode
– Remove electrode fixing screw
– Carefully remove electrode from bur-
ner
– Replace in reverse order
6.4 MAIN BURNER
– Turn off power supply
– Isolate gas supply
– Remove boiler cover
– Remove sealed chamber cover
– Disconnect gas connection at injector
– Disconnect air sensing tube
– Disconnect two plugs to fan
– Remove ignition electrode 6.3
– Disconnect ionisation electrode
– Remove 6 x 10mm nuts securing bur-
ner to heat exchanger
– Carefully lift out burner assembly
– Refit in reverse order
– Test for gas tightness.
6.5 FAN ASSEMBLY
– Remove burner assembly as descri-
bed in 6.4
– Remove 2 x 8mm bolts and loosen 2 x
8mm securing fan to burner assembly
– Remove restrictor plate and fit to
new fan
– Refit in reverse order
– Recommission boiler
– Test for gas soundness.
6.6 MAIN HEAT EXCHANGER
– Turn off power supply
– Isolate gas supply
– Isolate flow and return valves
– Drain boiler using drain vent
– Remove burner assembly as described
in 6.4
– Remove flue connection
– Disconnect flue sensor
– Disconnect limit stat
– Remove condensate drain connections
– Disconnect flow and return connections
– Remove two fixing brackets
– Lift out heat exchanger
– Refit in reverse order
– Recommission boiler
– Test for gas tightness.
6.7 FLUE SENSOR
– Turn off power supply
– Remove cover
– Remove sealed chamber cover
– Disconnect flue sensor
– Unscrew sensor
– Replace in reverse order.
6.8 100° SAFETY STAT
– Turn off power supply
– Remove cover
– Remove sealed chamber cover
– Disconnect 100° safety stat
– Remove fixing screws
– Refit in reverse order.
6.9 HEATING THERMISTOR
(SM SENSOR)
– Turn off power supply
– Remove cover
– Remove sealed chamber cover.
– Isolate flow and return valves
– Drain boiler using drain vent
– Disconnect thermistor
– Unscrew thermistor (catch any water
lost)
– Refit in reverse.
6.10 D.H.W. THERMISTOR
(SB) SENSOR
– Turn off power supply
– Remove cover see 4.4
– Isolate cold water supply valve
– Drain the cylinder
– Disconnect thermistor
– Unscrew thermistor (catch any water
lost)
– Refit in reverse.
6.11 GAS VALVE
– Turn off power supply
– Isolate gas supply
– Remove boiler cover see 4.4
– Disconnect wiring from gas valve
– Disconnect sensing tube
– Remove gas valve
– Refit in reverse order ensuring seals
are replaced as required
– Setting the gas valve procedure:
From the table below identify the boi-
ler type and gas used.
Connect flue gas analyser.
Ensure the capacity step shutter (5
fig. 16) to be fully open then switch on
the boiler.
Press and hold the button for a
few seconds to light the boiler:
– Press the
button
to ensure that
the boiler is on its minimum output:
(A) Adjust the capacity step shutter
(5 fig. 6) to achieve the CO2 value
shown in the table.
(B) Adjust the OFF-SET screw (6 fig.
16) to achieve the CO2 value shown in
the table.
– Press the
button to
ensure that
the boiler is on its maximum output.
Check the CO2 to be within the values
shown in the table, if necessary adju-
st with the capacity step shutter.
– Re-check and confirm the settings
at minimum and maximum output by
pressing and buttons.
– Check for gas tighhtness.
6.12 PRINTED CIRCUIT BOARD (PCB)
– Isolate from power supply
– Remove screw securing control panel
– Lower panel to horizontal position
– Remove PCB covers
– Disconnect all wiring
– Remove PCB fixing screws
– Ensure any PCB links are matched to
old board
– Reset PAR 1 and PAR 2 as per the
table 3.3.1
– Refit in reverse order
– Recommission boiler.
6.13 PUMP MOTOR
– Turn off power supply
– Remove boiler cover
– Isolate flow and return valves
NATURAL GAS
TYPE MIN MAX
(A) CO
2% (B) CO2%CO2%
25/55 9.0 ÷ 9.3 8.6 ÷ 8.9 8.7 ÷ 9.3
30/55 9.2 ÷ 9.4 8.7 ÷ 9.1 8.7 ÷ 9.3
LPG
TYPE MIN MAX
(A) CO2% (B) CO2%CO2%
25/55 9.9 ÷ 10.2 9.6 ÷ 9.9 9.6÷10.2
30/55 10.8÷ 11.0 9.7÷ 10.1 9.6÷10.1
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