72
ALTERNATING ‘L’ AND ‘1’ - FLOW TEMPERATURE OVERHEAT LOCKOUT
Is the Boiler and CH System lled with water and all
isolation and radiator valves open?
YES
Fill and vent the system and open all
isolation valves, then reset boiler
Is the Flow/Return Differential across the Boiler in
excess of 30°C?
NO
Check that the Pump is rotating freely. Is
the Differential now below 20°C?
YES
NO
Replace the Pump,
then reset boiler
NO
OK, now
reset boiler
YES
73
ALTERNATING ‘L’ AND ‘2’ - IGNITION LOCKOUT
If the boiler is reset does the boiler
ignite for a short time and then
extinguish?
YES
Is the Gas Pressure available at
the Boiler Inlet (>18 mbar)?
Check the detection electrode
and associated harness for:
continuity, visual condition and
position (Refer to Frame 49).
Check if the condensate pipe is
blocked.
Check ue is installed correctly.
Replace as necessary
NO
Check gas supply and
rectify fault
NO
YES
Is 215Vdc supply available at the
Gas Valve? (* See note)
YES
Check spark generator and
associated harness for: continuity
and visual condition. (Refer to
Frame 50) Are these functioning
correctly?
YES
Check ignition electrode and
associated harness for: continuity,
visual condition and position.
(Refer to Frame 48) Are these
functioning correctly?
NO
Check siphon and condensate
drain pipe work for blockage and
rectify if necessary. Boiler now
working OK?
Check wiring connection
from gas valve to PCB for
continuity. If the wiring is
OK then replace the PCB
NO
Replace Spark
Generator and harness
as necessary
NO
Replace Ignition
Electrode and
associated harness as
necessary
NO
Replace Gas Valve
YES
* Note: due to the wave form of the rectied voltage, the reading will vary depending on the type of meter used to measure the
value. In general terms a reading greater than 150V indicates that the correct voltage is supplied to the gas valve.
Unplug gas valve. Is resistance
between outside pins between 4k
Ω (± 2)?
YES
Replace Gas Valve
NO
RESET PROCEDURE - To reset boiler, turn mode knob to reset position and immediately turn knob back to required setting.
RESET PROCEDURE - To reset boiler, turn mode knob to reset
position and immediately turn knob back to required setting.
Check the Return Thermistors
(Refer to Frame 47)
Check resistance using a suitable multimeter
connected across the thermistor’s terminal pins
At 25
o
C expect 9,700 - 10,300 Ohms
At 60
o
C expect 2,400 - 2,600 Ohms
At 85
o
C expect 1,000 - 1,100 Ohms
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