Fault Finding
37
For Night Time Hot Water Function – ALL the following indicator lights MUST be lit
POWER If NOT lit this indicates a problem with power supply to the boiler - switched off or
possibly a blown fuse.
DHW PUMP If FLASHING this indicates either a store thermistor or PCB fault.
Refer to ‘Is the “DHW PUMP” Indicator flashing’ procedure in Section 12.2 (B)
FLOW If not lit this indicates either a lack of water flow or a possible flow switch problem.
DEMAND If not lit this indicates either timer/programmer is not ‘calling’ for hot water or ‘Hot Water’
switch is not set to ‘CONSTANT’.
BURNER If flashing this indicates PCB fault.
Refer to ‘Is the “BURNER” indicator lit’ procedure in Section 12.2 (B)
NOTE: The “DHW PUMP” indicator may be lit if the boiler is operating to heat the store which has priority over the CH operation.
There may be a delay before the “BURNER” indicator is lit when the the store is up to temperature.
For further guidance refer to the Main Fault Finding Procedures – Section 12.2.
A. No Central Heating - but Hot Water OK
First - Set Hot Water switch to OFF
Is the “DEMAND” NO Check programmer/timer and room thermostat are calling for heating.
indicator lit?
NO Check ‘Heating’ switch is set to ‘TIMED’.
Is the “CH PUMP” YES Check electrical connections at the pump.
indicator lit? PCB is supplying voltage Check for 230V at the pump terminals.
to the CH pump – but Check if CH pump is stuck:
pump is not working. Remove pump vent screw and check for Rotation of shaft/impeller.
If stuck: Rotate shaft manually to restart.
If still not operating; Replace the CH pump.
NOTE: A 6 metre pump must be used.
YES Check both pump valves are open.
CH pump is working Check Non-return valve on CH pump is operational (not sticking).
but no circulation. Check there are no air locks in the system. (if removal of air lock is
difficult – see additional check list).
Check the pump impeller is attached to the shaft.
Is the “CH PUMP” NO Check Non-return valve on CH pump - is it stuck blocked open -
indicator lit? check/rectify.
Note – CH return will be hotter than flow if CH non-return valve is
jammed open.
Check by closing one heating pump valve to stop circulation - does the
store then come up to temperature?
If problem is not due to CH non-return valve - continue to next check.
Is the “CH PUMP” YES First – set boiler ‘On/Off’ switch to ‘OFF’.
indicator flashing? Fast or Slow flash. Wait 5 seconds.
Then set ‘On/Off’ switch back to ‘ON’.
If the “CH PUMP” Fast flash Check CH ‘Flow‘ thermistor connection to PCB.
continues flashing. (twice per second): Indicates Replace ‘Flow’ thermistor.
a possible fault with the
‘Flow’ thermistor.
Slow flash(once every 2 seconds): Replace PCB.
Indicates a possible fault
with the PCB (relay).
Is the “BURNER” YES Is burner firing?
indicator lit? If NO: Refer to ‘BURNER NOT OPERATING’ Procedure -
Section 12.2 (C).
12.2 Main Fault Finding Procedures
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