Alpha CD12S, Installation And Servicing Instructions

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39
Alpha CD12S/20S/28S - Fault Finding
10.4 FAULT FINDING SOLUTIONS E to J
YES
Check and correct:-
1. Ignition electrode and lead
2. Electrode connections
3. Spark gap and position
4. Connections at ignition generator and PCB connector X8
5. Blocked flue
F
Is spark generator (T2)
making a clicking noise
Disconnect the plug from the spark generator.
PCB, X8 connector is 240V ac
across terminals 2, 3 during ignition
Replace PCB
Replace ignition
generator
NO
NO
YES
H
NO
Allow to cool. Continuity
across thermostat terminals
NO
YES
YES
Air in main heat exchanger.
Blocked heat exchanger/pipework
or pump not circulating water
Vent air, clear blockage Replace pump
Continuity across
thermal fuse
Replace overheat thermostat
Replace heat exchanger - remove the thermal fuse.
It is important to find the exact
cause of the overheat and rectify it before
operating the boiler with the new heat exchanger
Do not
Note:
J
Replace primary pressure switch
Replace PCB
Continuity across primary
pressure switch terminals
Unplug leads from primary pressure
switch, is there 5V DC at PCB across
X9 connector terminals 1 and 3
YES
NO
NO
E
Check pressure tubes are connected
PCB - X3 connector, is 240 V across terminals 1, 2
YES NO
Gas at burner
Replace gas valve Adjust gas valve
NO
NO
Ensure gas is on and purged
Replace PCB
G
Check and correct:-
1. Pressure tubes are connected and not blocked
2. If explosive ignition, check wiring to ignition generator is correct
3. Polarity
4. Flame sensing electrode and lead connections
5. Electrode position
I
NO
NO
YES
240V at internal clock
terminals 1 and 2
240V between terminal
block connection 1 and N
240V at PCB - X12 connector,
terminals 5 and N
Check wiring between PCB
and terminal block
Check wiring between clock
and main terminal block is correct
Make sure both channels are
switched on and check for 240V at
terminal block connections 2 and N
and 4 and N
NO
YES
Check external controls
are calling for heat
Replace clock
YES
NO