Alpha CD28X - Domestic Hot Water Troubleshooting Sequence

34
10.3 DOMESTIC HOT WATER- Follow operational sequence
Alpha CD25X/28X - Fault Finding
Turn thermostat to max.
Open DHW tap fully
DHW flow rate more
than 2.5 L/min.
DHW switch/diverter
valve fault
YES
YES
Turn selector to
Primary water is diverted from
CH system to DHW heat
exchanger.
DHW switch operated
Pump runs and
fan runs
Is mains
filter clean
YES
NO
NO
NO
YES
YES
Go to section ' ', page 35A
Neons A and B flashing
at the same time
Go to section ' ', page 35D
Burner output modulates
to maintain temperature
set at thermostat
NO
YES
DHW temp. sensor
and DHW heat
exchanger are clean
Reduce DHW flow rate
from 10 to 5 L/min.
Burner modulates
NO
YES
Close DHW tap
YES
DHW flow valve senses no
flow. Primary water diverted
to CH system.
DHW flow switch released (off)
Diverter valve/DHW switch fault
NO
YES
YES
Burner goes out
Fan stops after 50 seconds
YES
Operation sequence successful
Pump stops
YES
Go to section ' ', page 35D
YES
CH system pressure
too low. Re-pressurise
to 1.0 bar
Flue or
faulty fan
Primary/DHW
temperature sensor
fault
NO
Pump fault or primary
flow restricted
Go to section ' ', page 35B
Go to section ' ', page 36K
Go to section ' ', page 36J
Neon A and B
flashing alternately
Neon A flashing
Go to section ' ', page 35C
YES
YES
YES
Check gas valve
adjustment
Neon D illuminated continuously
Neon B illuminated cont.
Neon A flashing
Spark at ignition electrodes
for upto 10 seconds
YES
Burner lights
Neon C illuminated
YES
YES
NO
Reset by rotating
selector switch
Reset by rotating
selector switch
Overheat thermostat
or thermal fuse
has operated
Neon B illuminated
continuously
YES
Reset by rotating
selector switch
Neon B illuminated
continuously
Neon B flashing
NO
YES
If still no spark
Go to section ' ', page 36F
Go to section ' ', page 36E
If still illuminated,
Go to section ' ', page 36H
Neon B illuminated
continuously
YES
(BUT)
Go to section ' ', page 36G
Burner does not stay
alight after 10 seconds
YES
(BUT)