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7 SERVICING AND CHANGING COMPONENTS
(a) IMPORTANT: Before commencing a service or changing a component, ISOLATE
the mains electrical supply at the main isolator and TURN OFF the gas supply at
the service cock and when necessary turn off and drain the heating/domestic
water systems.
(b) To assist with a component identification and associated wiring refer to Figures
1.1, 1.2, 1.3, and 1.4.
(c) Before changing any part please check the part/stock code no/voltage ratings
are the same as the part being replaced.
7.1 GAS VALVE AND VENTURI
(a) The burner, gas valve, venturi and fan components form part of a sub-assembly,
which must be removed before one of them can be exchanged. Remove this
assembly by following the procedure detailed under ‘Routine Annual Servicing’.
Remove these components as a common assembly – then split and replace as
necessary.
(b) Disconnect the valve from the Venturi by removing the three torque head screws.
DO NOT MISPLACE THE SYNTHETIC RUBBER SEALING WASHER – BETWEEN THE
COMPONENTS.
(c) The Venuri is easily removed by unscrewing the 2 slotted pan head screws to
reveal the cork gasket. If the gas valve is to be replaced remove the male ½’’ gas
connection from the old valve. Fit it to the replacement valve using an approved
jointing compound.
(d) BEFORE re-assembling the gas valve/Venturi, check the soundness of the cork
gasket and rubber washer. Replace if deteriorated or damaged. Check and reset
gas rate and burner pressure page (see table 2.2)
(e) NOTE: Exchange of either gas valve or venturi will necessitate re-commissioning
of the appliance. This requires special equipment and should only be undertaken
if this equipment is available. The commissioning procedure is supplied with the
parts.
7.2 COMBUSTION AIR FAN
(a) Remove the main sub-assembly as stated above (Section 7.1 (a)) and remove the
gas valve/Venturi assembly.
(b) Disconnect the fan from the burner/adaptor casing by removing the (4) hexagon
nuts behind the mounting flange using a 7mm AF spanner.
(c) If necessary exchange the fan and re-assemble in reverse order.
(d) Replace the fan sealing gasket if the existing shows any signs of deterioration.
(e) Check boiler/controls operation.
7.3 BURNER – REMOVAL
(a) Remove the main sub-assembly as stated above (Section 7.1 (a)).
(b) Disconnect the burner from the burner/adaptor casing by removing the (4)
hexagon nuts on top of the casting using an 8mm AF spanner/socket.
(c) If necessary exchange the burner and reassemble in reverse order.
(d) REPLACE the fan sealing gasket if the existing shows any signs of deterioration.
(e) Check boiler/controls operation.
7.4 IGNITION AND FLAME SENSOR ELECTRODES
(a) Both components are removed in the same manner.
(b) Disconnect the appropriate lead.
(c) Ignition Electrodes – HT and EARTH
(d) Sensor – SENSOR LEAD
(e) Remove the (2) cross head screws retaining the component and carefully lift it
up out of the combustion chamber.
(f) If necessary exchange the component.
(g) ALWAYS fit a new ceramic sealing gasket.
(h) Re-assemble in reverse order.
(i) Check boiler/controls operation.
7.5 FLAME VIEWING WINDOW
(a) Remove the (2) cross head screws retaining
the frame.
(b) Lift off the frame and site glass.
(c) Clean/exchange the site glass as necessary
(d) ALWAYS fit new ceramic sealing gaskets.
(e) Re-assemble in reverse order.
7.6 DRY FIRING THERMOSTAT
(a) Pull off the leads on top of the thermostat.
(b) Unscrew the body (counter clockwise).
(c) If necessary exchange and re-assemble in
reverse order.
(d) Check boiler/controls operation.
7.7 STORE OVERHEAT THERMOSTAT (‘-SS’
MODEL ONLY)
(a) Remove (pull off) the leads from the back.
(b) Remove the central fixing nut.
(c) Remove the split pin at the thermostat phial
pocket and pull out the phial.
(d) Remove the thermostat.
(e) Replace as necessary and re-assemble in
reverse order. Finally depress thermostat
reset button.
(f) Check boiler/controls operation.
7.8 BOILER OVERHEAT THERMOSTAT
– REMOVAL
See 7.20.
7.9 PRESSURE GAUGE (‘-SS’ MODEL ONLY)
(a) Isolate the appliance from the heating
system.
(b) Isolate the cold supply to the primary
system/appliance at the quarter turn valve
on the inlet to the CA valve assembly.
(c) Open the safety valve to release internal
boiler pressure.
(d) Drain down the boiler to below the level of
the safety valve.
(e) Unscrew (counter clockwise) the capillary at
the valve using a 14mm AF spanner.
(f) Remove the knurled nut at the back of the
gauge and pull the capillary out through the
panel.
(g) If necessary exchange and re-assemble in
reverse order.
(h) Refill the boiler ensuring all air is removed.
(i) UNDERTAKE WATER SOUNDNESS TEST.
(j) Check boiler/controls operation.
SERVICING AND CHANGING COMPONENTS
Summary of Contents for GS A-Class 12/OV
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