Baxi Combi 105e Installation And Servicing Instructions page 39

Domestic Hot Water - Follow operational sequence
Turn selector to
neon illuminated
YES
Turn thermostat to
max. Open DHW tap fully.
DHW flow switch operated
YES
Primary water is diverted
from CH system to DHW
heat exchanger and flow
microswitch operated
neon illuminated
YES
Pump runs
YES
Primary flow switch
operated
YES
Fan runs at max speed
YES
Air pressure switch
proved
YES
Spark at ignition
electrodes for up to 10
seconds
YES
Burner on neon
illuminated
YES
Burner extinguishes
after 10 seconds
NO
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
NO
Go to section 'A'
Is mains water
filter and differential
assembly clean?
YES
NO
DHW flow rate more than
2.5l/min.
Continuity across DHW
NO
flow microswitch terminals
and PCB - A5 connector
terminals 5 & 6
NO
neon flashing
Go to section 'B'
NO
neon flashing
Go to section 'C'
NO
neon flashing
NO
neons flashing
Go to section 'D'
NO
neon flashing
Go to section 'E'
NO
neon flashing
NO
Replace PCB
NO
Go to section 'F'
YES neon flashing
Go to section 'I'
Reduce the DHW flow
NO
rate. If burner does not
modulate clean DHW
temperature sensor and
DHW heat exchanger. If
modulation does not occur
go to section 'G'
NO
Diverter valve spindle
assembly faulty
NO
Fan stops
14.0 Fault Finding
Replace diaphragm
YES
YES
DHW flow valve
diaphragm damaged
NO
DHW flow valve rod
obstructed
Replace DHW flow
NO
microswitch
YES
Replace PCB
Turn selector to reset
position. If regular
YES
resetting is required or
appliance still does not
operate investigation is
necessary
Turn the selector to the
YES
reset position. If the light
does not extinguish go to
section H & K
YES
Pump stops
Go to section 'J'
YES
Operation sequence
correct
39