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13.0 Fault Finding
CARRY OUT INITIAL FAULT FINDING CHECKS
1. Check that gas, water and electrical supplies are available at the boiler. Electrical supply =
230V ~ 50 Hz. CH water system pressurised to 0.5 bar when the boiler is cold. The preferred
minimum gas pressure is 19.5mbar (natural gas), 27mbar (butane) or 36mbar (propane).
2. Carry out electrical system checks, i.e. Ground Continuity, Resistance to Ground, Short Circuit
and Polarity with a suitable meter. Note: Repeat these checks after servicing or fault finding.
3. Ensure all external controls are calling for heat and check all external and internal fuses.
Before servicing or replacement of parts ensure the gas and electrical supplies are isolated.
Refer to Section 12.0 “Illustrated Wiring Diagram”
for position of numbered terminals
Turn selector to
neon illuminated
Primary flow switch
operated
Fan runs at max speed
Burner goes out
Pump runs
Turn thermostat
to max.
Is
neon illuminated ?
Air flow monitor
neon stays off
Red reset button
illuminated
Burner on neon
illuminated
Burner output
modulates until set
temperature is reached
Spark at ignition
electrodes for up to 10
seconds
Go to section ‘A’
Electrical supply at
neon PCB
Go to section ‘B’
Go to section ‘C’
Go to section ‘J’
Go to section ‘D’
Go to section ‘E’
Go to section ‘H’
Press to reset
Go to section ‘F’
Go to section ‘I’
Go to section ‘G’
Fan stops
Replace main PCB
Pump continues for
3 minutes
Replace 3-way valve
Operation sequence
correct
Boiler operates correctly,
C.H. remains cold
Check 230V at main PCB
M3 connectors 6,7
Check continuity of the
wiring
Safety Thermostat
neon illuminated
Press white reset button.
If neon stays
illuminated or if boiler
requires regular resetting,
investigation is necessary
neon illuminated
External controls calling
for heat
Ensure controls are set to
demand and verify the
contacts are closed
If still illuminated,
go to section ‘K’
Burner extinguishes
after 10 seconds
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
YES
NO
NO
Replace neon PCB
NO
YES
Replace main PCB
Internal clock (if fitted)
is calling for heat
Go to section ‘L’
Set clock
YES
NO
Central Heating
- Follow operational sequence
Diverter valve operated
i.e.primary water diverted
to the CH system
Electrical supply at
diverter valve
Replace valve or head
Check valve wiring - if OK
replace main PCB
YES
NO
YES
YES
NO
