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Page 34
(f) Remove the split pin and pull out the control/OH thermistor from its pocket.
(g) Disconnect the union connectors (2) at the inlet and outlet of the electric boiler
using a 37mm AF spanner and remove it.
(h) Unscrew the cable from the earth tag.
(i) When removing the electric boiler take precautions against any standing water
in the pipework.
(j) Replace if necessary and reassemble in reverse order.
(k) UNDERTAKE WATER SOUNDNESS TEST.
(l) Replace any cable ties.
(m) Check boiler/controls operation
7.20 BOILER OVERHEAT THERMOSTAT / ELECTRIC BOILER CONTROL
THERMOSTAT
(a) Isolate and drain down as necessary the primary water system.
(b) Remove the 4 way electrical connector from the thermistor
(c) Unscrew using a 15mm AF spanner and remove the thermistor
(d) Replace as necessary and reassemble in reverse order making a watertight seal
using PTFE tape.
(e) Refill primary system
(f) Undertake water soundness test
(g) Check boiler/ controls operation
7.21 DHW PUMP
(a) Close the isolation valves on the inlet and outlet of the pump.
(b) Remove the protective cover from the pump terminal block and disconnect the
supply cable from the quick release terminals.
(c) Unscrew the 4 securing bolts using a 4mm allen key and remove the pump
head.
(d) NOTE: SOME RESIDUAL WATER FROM THE PUMP HOUSING IS UNAVOIDABLE.
(e) Replace if necessary and re-assemble in reverse order.
(f) UNDERTAKE WATER SOUNDNESS TESTS
(g) Check boiler/controls operation.
7.22 BOILER/CH PUMP
(a) Close the isolation valves on the inlet and outlet of the pump.
(b) Remove the protective cover from the pump terminal block and disconnect the
supply cable from the quick release terminals.
(c) Unscrew the 4 securing bolts using a 4mm allen key and remove the pump
head.
(d) NOTE: SOME RESIDUAL WATER FROM THE PUMP HOUSING IS UNAVOIDABLE.
(e) Replace if necessary and re-assemble in reverse order.
(f) UNDERTAKE WATER SOUNDNESS TEST.
(g) Check boiler/controls operation.
7.23 AUTOMATIC AIR VENT
(a) Gently unscrew the cylindrical top part of the valve (above the hexagonal nut) by
hand checking no water is released. If no water is released replace the top part
only of the valve.
(b) If water is released drop the system pressure using the safety relief valve (SS model
only) and then drain down the boiler to below the level of the AAV. Unscrew the
hexagonal bottom part of the valve incorporating a non return valve using a
22mm AF spanner.
(c) Replace the total valve using PTFE tape on the threads to make watertight.
(d) UNDERTAKE WATER SOUNDNESS TEST.
(e) Check boiler/controls operation.
7.24 BYPASS VALVE
(a) Isolate the boiler from the heating system.
(b) With the SP model drop the system pressure using the safety relief valve and then
drain down the boiler to below the level of the bypass valve.
(c) Release the two jubilee clips and remove the flexible air inlet hose.
(d) Unscrew the union connection on the
heating flow to the right of the bypass valve
using a 40mm AF spanner.
(e) Unscrew the bottom inlet nut of the bypass
valve.
(f) Remove the bypass valve and pipework
assembly and unscrew the outlet nut of the
byepass valve.
(g) Replace the bypass valve and reassemble
in reverse order using new washers on
the heating flow and expansion vessel
connections.
(h) On the SP model unscrew the nut on
the flexible connector to the expansion
vessel using a 30mm AF spanner taking
precautions against any standing water in
the hose.
7.25 CA VALVE – (SP MODEL ONLY)
(a) Isolate the 2 quarter turn valves either side of
the CA/pressure reducing valve assembly.
(b) Unscrew the 2 union nuts either side of the
CA valve using a 37mm AF spanner push
off the silver bezel on the connection to
the tundish and remove the valve.
(c) When removing the valve take precautions
against any standing water in the valve.
(d) Replace the valve and reassemble in reverse
order making sure the new valve is inserted
in the correct direction (arrow down) and the
2 washers are replaced.
(e) UNDERTAKE WATER SOUNDNESS TEST.
(f) Check boiler/controls operation.
7.26 PRESSURE REDUCING VALVE (‘-SS’
MODEL ONLY)
(a) Isolate the quarter turn valve on the inlet
(top) of the CA valve assembly.
(b) Isolate the heating system and drain down
the boiler.
(c) Disconnect the compression nut on the
outlet of the quarter turn valve (bottom)
below the pressure reducing valve using a
24mm AF spanner.
(d) Disconnect the union nut on the inlet
(above) the pressure reducing valve using
a 37mm AF spanner and remove the valve/
assembly.
(e) Replace the valve in the assembly and
reassemble in the boiler in reverse order
making sure to replace the washer in the
union connector.
(f) UNDERTAKE WATER SOUNDNESS TEST.
(g) Check boiler/controls operation.
7.28 3- WAY HYDRONIC VALVE ACTUATOR
(Figure 6.4)
(a) Depress the tab and unplug the 3 way
connector from the left hand side of the
actuator.
SERVICING AND CHANGING COMPONENTS
Summary of Contents for GS A-Class 12/OV
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