Alpha CD25C Installation And Servicing Instructions page 34

10.3 DOMESTIC HOT WATER- Follow operational sequence
Turn selector to
Neon D illuminated continuously
YES
Turn thermostat to max.
Open DHW tap fully
YES
Primary water is diverted from
CH system to DHW heat
exchanger.
DHW switch operated
YES
Pump runs and
fan runs
YES
YES
(BUT)
Spark at ignition electrodes
for upto 10 seconds
YES
Burner lights
Neon C illuminated
YES
Burner output modulates
to maintain temperature
set at thermostat
YES
Close DHW tap
YES
DHW flow valve senses no
flow. Primary water diverted
to CH system.
DHW flow switch released (off)
YES
Burner goes out
Alpha CD25C/28C/35C - Fault Finding
34
NO
Go to section '
NO
DHW flow rate more
than 2.5 L/min.
YES
DHW switch/diverter
valve fault
Neon B illuminated cont.
NO
Neon A flashing
Neon A and B
flashing alternately
Neon A flashing
Neons A and B flashing
at the same time
NO
Neon B illuminated
continuously
Neon B illuminated
continuously
NO
Neon B flashing
YES
(BUT)
Burner does not stay
alight after 10 seconds
Reduce DHW flow rate
NO
from 10 to 5 L/min.
Burner modulates
NO
Diverter valve/DHW switch fault
YES
Pump stops
A ', page 35
NO
Is mains
filter clean
YES
Pump fault or primary
flow restricted
CH system pressure
YES
too low. Re-pressurise
to 1.0 bar
Primary/DHW
YES
temperature sensor
fault
Flue or
YES
faulty fan
YES
Reset by rotating
selector switch
YES
Reset by rotating
selector switch
YES
Overheat thermostat
operated
Neon B illuminated
continuously
DHW temp. sensor
NO
and DHW heat
exchanger are clean
YES
Check gas valve
adjustment
YES
Fan stops after 50 seconds
Operation sequence successful
Go to section '
Go to section '
Go to section '
Go to section '
Go to section '
If still no spark
Go to section '
Go to section '
If still illuminated,
Go to section '
Reset by rotating
selector switch
Go to section '
Go to section '
YES
K ', page 36
B ', page 35
J ', page 36
C ', page 35
D ', page 35
F ', page 36
E ', page 36
H ', page 36
G ', page 36
D ', page 35