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21
221764B
10 Fault Finding - Electrical
Diagram 10.2
ELECTRICAL FAULT FINDING
1526
START
Isolate electricity supply at the external isolator. Remove the mains inlet connector and cover to expose
supply cable connections. Reconnect inlet connector, restore power. Is there 220 to 240V between 'L' and 'N'?
Isolate electricity supply to the unit at the
external isolator. Remove the control box cover.
Check continuity of red cable between terminal
'L' in the inlet connector and Thermostat terminal 'C'.
Is there continuity?
Check that all remote time or temperature
controls are calling for duty.
Turn boiler thermostat to maximum. Connect
ohmmeter across thermostat terminals 'NC' and 'C'.
Is there continuity?
Faulty cable, renew.
Faulty thermostat, renew
Faulty cable, renew.
Faulty cable, renew.
Turn boiler thermostat OFF.
Is continuity interrupted?
Connect ohmmeter and check the continuity
of brown cable between terminal 'L' on gas
valve plug and terminal 'NC' at thermostat.
Is there continuity?
Connect ohmmeter between terminal 'N' in
inlet connector and gas valve plug terminal 'N'.
Is there continuity?
Disconnect ohmmeter and reconnect gas valve plug.
Restore power to unit. Does burner light?
Boiler in order. Isolate electricity supply and
refit mains inlet connector cover.
Carry out preliminary electrical system checks to make sure that the electricity supply is available at the boiler.
Check that any remote time or temperature controls are calling for duty. Make sure that the system is filled,
the gas supply is available and the pilot is lit.
NO
NO
NO
NO
NO
NO
Faulty gas valve, renew.
NO
YES
YES
YES
YES
YES
YES
YES
FUNCTIONAL FLOW WIRING
Diagram 10.1
4708
BLUE
N
N
L
VIEW OF
PLUG
WHEN
REMOVED
E
BROWN
BLACK
THERMOSTAT
N/C
C
GAS VALVE
CONTROL SOLENOID
L
10.1 Electrical
IMPORTANT, the preliminary electrical system checks as
contained in the British Gas Multimeter Instruction book or
similar publication, are the first checks to be carried out during
a fault-finding procedure. On completion of the service
fault-finding task which has required the breaking and remaking
of electrical connections then checks, earth continuity, polarity
and resistance to earth must be repeated.
Refer to functional flow diagram 10.1 electrical fault finding
chart, diagram 10.2 and wiring diagram 9.5.