Main Fault Finding Procedure - Grant Combi 26e Installation And Servicing Instructions

For night time Hot Water Function – aLL the following indicator lights mUSt be lit
POWER
DHW PUMP
FLOW
DEMAND
Water'
BURNER
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.
12.2 main Fault Finding Procedures
a. no Central Heating - but Hot Water OK
First - Set Hot Water switch to OFF
NO
Is the "DEMAND"
indicator lit?
NO
Is the "CH PUMP" YES
indicator lit? PCB is supplying voltage
to the CH pump – but
pump is not working.
YES
CH pump is working
but no circulation.
Is the "CH PUMP" NO
indicator lit?
Is the "CH PUMP" YES
indicator flashing? Fast or Slow flash.
If the "CH PUMP" Fast flash
continues flashing. (twice per second): Indicates
a possible fault with the
'Flow' thermistor.
Slow flash(once every 2 seconds):
Indicates a possible fault
with the PCB (relay).
Is the "BURNER" YES
indicator lit?
If NOT lit this indicates a problem with power supply to the boiler - switched off or
possibly a blown fuse.
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)
If not lit this indicates either a lack of water flow or a possible flow switch problem.
If not lit this indicates either timer/programmer is not 'calling' for hot water or 'Hot
switch is not set to 'CONSTANT'.
If flashing this indicates PCB fault.
Refer to 'Is the "BURNER" indicator lit' procedure in Section 12.2 (B)
Check programmer/timer and room thermostat are calling for heating.
Check 'Heating' switch is set to 'TIMED'.
Check electrical connections at the pump.
Check for 230V at the pump terminals.
Check if CH pump is stuck:
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.
Check both pump valves are open.
Check Non-return valve on CH pump is operational (not sticking).
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.
Check Non-return valve on CH pump - is it stuck blocked open -
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.
First – set boiler 'On/Off' switch to 'OFF'.
Wait 5 seconds.
Then set 'On/Off' switch back to 'ON'.
Check CH 'Flow' thermistor connection to PCB.
Replace 'Flow' thermistor.
Replace PCB.
Is burner firing?
If NO: Refer to 'BURNER NOT OPERATING' Procedure -
Section 12.2 (C).
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