Glow-worm Xtrafast 96-120 - Manual (Page 34)

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Note: Apply a small quantity of silicon grease to the safety valve
'O' ring prior to fitting.
• Open isolating valves on flow and return connections, refill,
vent and pressurise boiler.
• Check for leaks.
19.19 Domestic safety valve (10 bar), refer to
diagram 19.14.
Before starting refer to the front of Section 19 Important
information.
If safety valve seating is damaged, it will be necessary to
replace safety valve as a complete unit, repair is not possible.
• Remove the base panel, secured with four screws and hooked
in at the rear, see diagram 19.14.
Drain down the boiler, refer to relevant part of Section 19.8.
• Disconnect safety valve discharge pipe from safety valve.
• Remove wire clip securing safety valve to domestic hot water
outlet fitting and remove safety valve.
• Fit replacement safety valve.
Note: Apply a small quantity of silicon grease to the safety valve
'O' ring prior to fitting.
• Open isolating valves on flow and return connections, refill,
vent and pressurise boiler.
• Check for leaks.
19.20 Main heat exchanger, refer to diagram
16.5 and 19.15.
Before starting refer to the front of Section 19 Important
information.
• Remove the front panel, refer to Section 16.3.
• Lower the control panel, refer to Section 16.4.
• Remove the sealed chamber cover, refer to Section 16.5.
• Remove the combustion chamber cover, refer to Section
16.7.
Drain down central heating water circuit and drain the boiler,
refer to relevant part of Section 19.8.
• Disconnect power supply leads and earth lead from fan.
• Unscrew and remove two fan retaining screws from the right
hand side edge of fan mounting plate.
• Remove fan with mounting plate attached by pulling forward
and out of boiler.
• Remove air pressure switch sensing tube from sensing probe
on flue hood.
• Remove screws securing flue hood to rear panel
• Lift flue hood clear of heat exchanger.
• Unclip overheat thermostat from heating flow pipe.
• Pull out slotted metal clips securing pipes from heat exchanger.
• Lift heat exchanger up and forwards to remove from boiler
taking care not to damage insulation.
DO NOT DAMAGE PAINTED FINISH OF HEAT EXCHANGER.
• Fit replacement heat exchanger.
Note: When re-fitting fan, make sure that the two lugs on the fan
mounting plate engage in the flue hood.
19.16 Gas safety valve, refer to diagram 19.13.
Before starting refer to the front of Section 19 Important
information.
• Remove the front panel, refer to Section 16.3.
• Lower the control panel, refer to Section 16.4.
• Remove gas control valve assembly, refer to Section 19.15.
• Locate gas safety valve on the rear of the gas valve.
• Unscrew and remove the 2 screws securing the gas safety
valve to the gas control valve.
• Fit replacement gas safety valve in reverse order to removal
taking care not to damage the ‘O’ ring.
• Refit electrical connections, the polarity of the wires to the
modulating coil is not important.
• Refit electrical connector to the gas safety valve.
• Fit replacement gas control valve assembly into boiler.
• Reconnect gas pipes.
• Refit electrical connections in reverse order to removal.
19.17 Spark ignition unit, refer to diagram
19.13.
Before starting refer to the front of Section 19 Important
information.
• Remove the front panel, refer to Section 16.3.
• Lower the control panel, refer to Section 16.4.
• Disconnect electrical connections from spark ignition unit.
• Remove screw securing spark ignition unit to gas valve
mounting bracket.
• Replace spark ignition unit.
19.18 Heating safety valve (3 bar), refer to
diagram 19.14.
Before starting refer to the front of Section 19 Important
information.
• Remove the front panel, refer to Section 16.3.
• Lower the control panel, refer to Section 16.4.
If safety valve seating is damaged, it will be necessary to
replace safety valve as a complete unit, repair is not possible.
Drain down central heating water circuit and drain the boiler,
refer to relevant part of Section 19.8.
• Remove the base panel, secured with four screws and hooked
in at the rear.
• If lt is not possible to remove the safety valve securing pin
(without straining the pipe work), to remove the safety valve.
Continue following the removal instructions below.
• Remove the heating flow isolating valve by disconnecting the
two union nuts and removing the securing clip.
• Disconnect the heating flow union nut at the safety valve
housing.
• Disconnect safety valve discharge pipe from safety valve.
• Remove the safety valve and housing.
• Remove safety valve securing pin.
• Remove safety valve.
• Fit replacement safety valve.