Alpha CD28X - Fault Finding Solutions E-K

36
Alpha CD25X/28X - Fault Finding
10.5 FAULT FINDING SOLUTIONS E to K
NO
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
YES
NO
YES
NO
YES
240V at internal clock
terminals 1 and 2
I
240V at PCB - X12 connector,
terminals 5 and 1
240V at PCB - X12 connector, terminals 5 and 1
Wiring between clock
and PCB is correct
YES
YES
NO
YES
Continuity across
clock terminals 3 and 4
Internal clock calling for heat
Wiring between clock
and PCB is correct
Replace clock
Check external controls
are calling for heat
YES
YES
NO
J
Replace primary pressure switch
Replace PCB
Continuity across primary
pressure switch terminals
Unplug leads from primary pressure switch
5 V DC at PCB across X9 connector terminal 1 and 3
YES
NO
NO
YES
YES
YES
YES
YES
YES
Replace PCB
Replace PCB
Replace lead
Replace motor
Replace valve
Replace DHW flow switch
Continuity across DHW
flow switch (hot tap on)
Diverter valve spindle operating
Check DHW heat exchanger for blockage
Check by-pass valve is not stuck open
36 V DC at PCB across X4 connector terminal 3 and X13 connector terminal 3
240 V AC at PCB across X15 connector terminals 4, 5
Remove the diverter valve motor, is the brass piston
fully extended (flush with plastic housing)
Flow rate above 2.5l/min
Check mains supply.
Clean mains inlet filter
Check continuity of
motor plug and lead
NO
NO
YES
NO
NO
NO
NO
NO
NO
K
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
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
H
NO
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 - t 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 no
Note: