Technical data

31
10 FAULT FINDING
10.1 CARRY OUT INITIAL FAULT FINDING CHECKS
1. Check that gas, water and electrical supplies are available at the boiler.
i.e. Inlet gas pressure = 20 mbar, Electrical supply = 230/240 V ~ 50 Hz, CH water system pressurised to 1 - 1.5 bar
2. Carry out electrical system checks, i.e. Earth Continuity, Resistance to Earth, Short Circuit and Polarity with a suitable meter.
Note: These checks must be repeated after any servicing or fault finding.
3. Ensure all external controls are calling for heat and check all external and internal fuses.
Before any servicing or replacement of parts ensure the gas and electrical supplies are isolated.
10.2 CENTRAL HEATING - Follow operational sequence
YES
YES
Pump runs
Diverter valve operated,
i.e. primary water diverted
to CH system
NO
NO
Go to section ' ', page 33
B
Differential flow switch
operated
NO
YES
Go to section ' ', page 33
C
Fan runs at max. speed
NO
YES
Go to section ' ', page 33
D
Go to section ' ', page 34
J
NO
YES
YES
Turn thermostat to max.
neon illuminated
External controls
calling for heat
If fitted, internal
clock calling for heat
Has DHW demand
been satisfied
240 V across main
terminal block,
terminals 1 and N
YES
Replace relay PCB
Relay energised
and contacts closed
i.e. continuity between
terminals 14, 15 on
PCB - M4 connector
PCB - M1 connector,
is 2V DC across
terminals 49, 51
Replace main PCB
Replace main PCB
Is diverter jammed,
if so release
Replace diverter
valve/motor
Replace neon PCB
NO
NO
NO
YES
NO
YES
YES
YES
NO
Turn selector to
neon illuminated
Go to section ' ', page 33
A
Go to section ' ', page 34
L
YES
neon
illuminated
Press white reset
button, if neon
stays illuminated
Air pressure switch proved
neon stays off
neon
illuminated
YES
NO
YES
Go to section ' ', page 33
E
Spark at ignition electrodes
for upto 10 seconds
YES
NO
YES
Press red button to reset
Go to section ' ', page 34
H
Red reset button
illuminated
NO
YES
Burner lights
YES
Go to section ' ', page 33
F
Go to section ' ', page 34
I
Burner output modulates until
set temperature is reached
NO
YES
Burner goes out
YES
Fan stops
YES
Operation sequence successful
Pump continues to run for
3 minutes
YES
Go to section ' ', page 34
G
But, burner does not stay
alight after 10 seconds
If still illuminated,
Go to section ' ', page 34
K
240V at:-
1. Main PCB - M12 connector,
terminals 24, 26
2. Diverter valve motor
Alpha 500E - Fault Finding