19
6.5
C.H. MODE - FAULT FINDING
Start from cold
Summer/Winter switch set to WINTER position.
Room thermostat (if fitted) calling for heat and all D.H.W. taps off.
C.H. thermostat set to maximum position.
Clock override switch in the on position.
NOTE:
After completing fault finding reset the room thermostat (if fitted) to the required setting and turn the clock over-
ride switch to the clock position. If the appliance will not function on “clock” setting check the wiring to the clock
and if necessary, replace the clock.
Is power at
the external
socket?
Make
power
available
Does
the pump
start?
Does
the fan
start?
Replace
the stat
Is there a spark at
the pilot?
Is fuse
at mains
plug OK?
Is power at
L and N
terminals?
Is the
over heat
thermostat
correctly set?
Can the
thermostat
be reset?
Reset the
thermostat
Make it
free to
rotate
Replace fuse in
mains plug
Check wire
connections
to L and N
terminals
Is there
240 V supply
to pump?
Is there
240 V supply
to fan?
Replace
fan
Check gap
between
electrode and
hood.
Check H.T. lead
and electrode
are not damaged.
Does it
now spark?
Is pump
shaft free
to rotate?
Replace
driver PCB
Is limit
thermostat
calling for heat?
Replace
limit thermostat
Replace
pump
Is driver PCB F1
fuse OK?
Is driver PCB F2
fuse OK?
Remove connector
No. 26 to 29.
Does the
fan start?
Replace C.H.
thermistor
Has pressure
switch
operated?
Replace
F2 fuse
Replace
F1 fuse
Does the relay K2
(Driver PCB)
change position?
Replace
ignition PCB
Check
sensing pipe
connections
and check
for blockages.
Does it
now operate?
Replace
ignitor PCB
Replace
driver PCB
Replace
pressure switch
Does the
pilot light?
Does spark
stop after
pilot is lit?
Does main burner
crosslight from
pilot?
Can burner
pressure be
reduced via
C.H. ajuster?
Does burner
pressure reduces
as temperature
rises toward max.?
Verify:
1) Limit stat
2) C.H.
thermistor
3) Driver PCB
Is main burner
pressure
achieved?
Replace
ignition PCB
Replace C.H.
thermistor
Does the boiler
swich OFF before
temp. attainment?
Is there a
voltage at the
modulator coil?
Is there a gas
supply to pilot?
Open
gas cock
Replace
proportioning
unit (Modulator)
Is pilot injector
free from
blockages?
Clean or replace
pilot injector
Is there electr.
supply at the
pilot solenoid?
Replace
ignition PCB
Is there electr.
supply at the
main solenoid?
Replace
gas valve
Boiler
satisfactory
Replace main coil.
Does main
burner crosslight?
Replace
pilot solenoid
Yes
No
Yes
No
No
No
Yes
Yes
No
No
Yes
Yes
No
No
Yes
Yes
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Yes
No
Yes
No
No
No
Yes
Yes
No
Yes
No
No
Yes
No
No
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
No
No
No
Yes
Yes
No
No
Yes
Yes
Yes
No
No
Yes
No
No
No
No
Yes
