30
221873B
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
F
G
E
D
C
B
A
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
Check appliance installation and
that it is mechanically correct.
Check filters are clean and allow
adequate water flow.
Is mains L.E.D. illuminated.
Open a tap to create demand.
Demand L.E.D. illuminated.
Check flow switch operation.
Check the pump is not mechanically stuck.
Pump starts.
Fan starts.
Start spark.
Domestic hot water operates.
Switch to central heating demand.
Demand L.E.D. illuminates.
Follow B-G.
Gas control valve opens at
ignition rate (5-6 mbar).
Burner pressure increases
to full rate.
Turn control thermostat or flow
rate down to induce modulation.
Check fuses and power supply.
If lockout L.E.D. is illuminated, press reset.
Check 230V supply to pump.
Check 230V
supply to fan.
Check spark electrodes
and cables.
If domestic hot water demand is still illuminated.
Faulty domestic hot water switch.
Correct operation.
Check gas control
valve cables.
Goes to lockout.
Is heating circuit
getting hot.
Check air pressure
switch operation.
Check thermistor.
Unplug fan and check
coil resistance.
Check air pressure switch status
and operation.
Check gas control
valve voltage.
Check sensing electrode
and cables.
Check 3 way
valve operation.
Check primary circuit
overheat continuity.
Check venturi and
connecting tubes.
Check burner for
cross lighting.
Unclip motor. Turn domestic hot water
Off and On. Does pin move in and out.
Manually push brass splindle in diverter
valve. Does domestic hot water get hot
when pushed in and central heating
water get hot when released.
Replace motor.
13 Fault Finding
Diagram 13.3
7402
