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NO
IS THERE A LIVE SUPI'I. Y TO
RI:PLACE HEATING THERMOSTAT.
I
TERMINAL 7?
t
YES
NO
CONNECT A MANOMETER TO THE
REPLACE GAS VALVE.
OUTLET PRESSURE TEST PORT OF
THE GAS VALVE !SEE FIG. 121.
SET J.POSITION SWITCH TO OFF OR
IF PROGRAMMER IS FITTED SET HW
& CH SELECTORS TO OFF. LIGHT
PILOT. SET THE 3-POSITION SWITCH
TO HW & CH. OR IF A PROGRAMMER
IS FITTED SET TO HW & CH ON
DOES MAIN BURNER LIGHT?
YES
NO
NO
DOES MAIN BURNER STAY ALIGHT
r
NO CIRCULATION AROUND HEATING
f------1
REPLACE CIRCULATING PUMP.
J
WITHOUT BOILING AND WITH THE
SYSTEM. CHECK RADIATOR VALVES
PILOT STAYING AUGHT?
ARE OPEN AND AIR HAS BEEN
VENTED. DOES MAIN BURNER STAY
AUGHT?
YES
!
YES
NO
YES
REMOVE THE CAP FROM THE LOWER
TEST INCOMING SUPI'I. Y PRESSURE
rn
REPLACE GAS VALVE AND ADJUST
I
PRESSURI: GOVERNOR. ADJUST GAS
TO API'I.IANCE. IS THIS A MINIMUM
PRESSURE.
PRESSURI: TO 14.0 m.bar 15.6 in.wgJ.
OF 20 bar 18 in.wgl AT THE
CAN PRI:SSURI: BE SET?
API'I.IANCE?
lNO
NO
RECTIFY SUPI'\.Y FAULT. CAN
PRESSURE BE SET TO 14 m.bar
15.6in.wg)?
YES
~YES
NO
NO
REDUCE HEATING LOAD OF BOILER
DOES PILOT LIGHT GO OUT BEFORE
1
~r
. . , , . .
M.OHXCfSSM •
1
TO TWO TO THREE RADIATORS.
SYSTEM HAS REACHED CORRECT
TEMPERATURE 1>85-90'C APPROXJ
DOES MAIN BURNER CYCLE ON
OPERATING TEMPERATURE'
AND THE PILOT GO OUT?
HEATING THERMOSTAT?
NOMINALLY 7B-82'C
l
YES
NO
REPLACE HIGH LIMIT THERMOSTAT.
L
REPLACE HEAliNG THERMOSTAT.
I
DOES SYSTEM CYCLE NORMALLY?
YES
!YES
NO
SET THE J.POSITION SWITCH TO HW
f-------
REMOVE THE CAP FROM THE UPPER
NO
I~ REPLACE GAS VALVE.
I
ONLY OR IF A PROGRAMMER IS
PRESSURE GOVERNOR ON THE GAS
FITTED SELECT HW ON. CH OFF
VALVE. CAN PRESSURE BE
TURN HOT WATER THERMOSTAT TO
ADJUSTED BETWEEN 1.8-14m.bar
MAXIMUM. DOES MAIN BURNER
10.7-5.6 in.wg.J?
PRESSURE INCREASE TO 14 m.bar
l "'
15.6in.wg.l'
YES
NO
REPLACE WATER DIVERTING VALVE.
I
DID THE WATER DIVERTING VALVE
CLOSE WHEN THE HOT WATER
THERMOSTAT WAS TURNED TO
MAXIMUM?
.
YES
NO
YES
AFTERAPPROX 10-20MINUTESDO
I
DOESTHEHOTWATERLIMIT
,liSTHEHOTWATERHEAT
YES
REPLACE HOT WATER PRIORITY
THE RELAY CONTACTS OPEN AND
THERMOSTAT OPERATE-INDICATED
EXCHANGER ABOVE BO'C.
THERMOSTAT.
I
THE MAIN BURNER TURN OFF?
BY THE MAIN BURNER GOING OUT
BUT THE RELAY CONTACTS
STAYING CLOSED.
i.e. NOLIVESUPPLYATT5'
~NO
DOES THE PILOT LIGHT GO OUT
AND/OR THE SYSTEM BOIL? REPLACE
BOTH THE HOT WATER CONTROL
AND THE HOT WATER LIMIT
THERMOSTATS.
YES
~
DOES THE CIRCULA liNG PUMP
CONTINUE TO RUN FOR
APPROXIMATELY 5 MINUTES AND
THEN STOP>
YES
SET THE J.POSITION SWITCH TO HW
& CH, OR IF A PROGRAMMER IS
FITTED SET TO HW ON. CHON
WAIT UNTIL THE RELAY CONTACTS
OPEN AND THE BOILER IS IN A
CENTRAL HEATING MODE
RESET THE CENTRAL HEATING GAS
PRESSURE TO THAT SHOWN BY THE
ARROW ON THE DATA PLATE
CYCLE FINISHED.
NO
NO
I
REPLACE HOT WATER LIMIT
THERMOSTAT.
I
REPLACE PUMP OVER-RUN CIRCUIT.
I
NOTE: Preliminary electrical system chec ks as contained in the BGC
rst electrical·checks to be
ure. On completion of the
equired the breaking and
Multimeter Instructions Book are the fi
carried out during a fault finding proced
Service Fault Finding task which has r
remaking of electrical connections, the n the checks-A, EARTH
T ANCE TO EARTH-MUST
CONTINUITY, C, POLARITY and
D,
RESIS
be repeated.
29
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