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Domestic Hot Water - Follow operational sequence
Turn selector to
neon illuminated
YES
Turn
thermostat to max.
Open DHW tap fully. DHW
flow switch operated
YES
Primary water is diverted
from CH system to DHW heat
exchanger and flow micro-
switch operated
neon illuminated
YES
Pump runs
YES
Primary flow switch operated
YES
Fan runs at max speed
YES
Air pressure switch proved
YES
Spark at ignition electrodes
for up to 10 seconds
YES
Burner on
neon illumina-
ted
YES
Burner extinguishes
after 10 seconds
NO
Burner output modulates to
maintain temperature set at
thermostat
YES
Close DHW tap
YES
DHW flow valve senses no
flow.
Primary water diverted to CH
system. DHW flow switch
released off
YES
Burner goes out
NO
Go to section 'A'
Is mains water filter and diffe-
rential assembly clean?
YES
NO
DHW flow rate more than
2.5l/min.
Continuity across DHW flow
NO
microswitch terminals and
PCB - A5 connector terminals
5 & 6
NO
neon flashing
Go to section 'B'
NO
neon flashing
Go to section 'C'
NO
neon flashing
NO
neons flashing
Go to section 'D'
NO
neon flashing
Go to section 'E'
NO
neon flashing
NO
Replace PCB
NO
Go to section 'F'
YES
neon flashing
Go to section 'I'
NO
Reduce the DHW flow rate.
If burner does not modulate
clean DHW temperature
sensor and DHW heat
exchanger. If modulation
does not occur go to section
'G'
NO
Diverter valve spindle assem-
bly faulty
NO
Fan stops
Replace diaphragm
YES
YES
DHW flow valve diaphragm
damaged
NO
DHW flow valve rod
obstructed
NO
Replace DHW flow micro-
switch
YES
Replace PCB
Turn selector to reset posi-
tion. If regular resetting is
YES
required or appliance still
does not operate investiga-
tion is necessary
Turn the selector to the reset
YES
position. If the light does not
extinguish go to section H &
K
YES
Pump stops
36
Go to section 'J'
YES
Operation sequence correct
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