Baxi Combi Instant 80 HE Installation & Servicing Instructions Manual page 43

Domestic Hot Water - Follow operational sequence
Turn On/Off/Reset selector to
position.
neon illuminated.
YES
Primary water diverted to
DHW preheating circuit.
YES
Turn preheat control to on.
Preheating function starts after
25 seconds.
neon flashing.
YES
Open DHW tap fully. DHW
flow switch operated.
YES
Primary water is diverted from
preheating circuit to DHW
heat exchanger.
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 electrode for
up to 10 seconds.
YES
Burner lights.
YES
Burner extinguishes after 10
seconds.
NO
Burner output modulates to
maintain temperature set at
preheat control.
YES
Close DHW tap.
YES
DHW flow valve senses no
flow. DHW flow switch
released off.
YES
Preheating function restarts.
neon flashing
YES
YES
Burner goes out.
NO
Go to section 'A'.
NO
Go to section 'M'.
External controls and where
NO
fitted, integral timer calling for
heat.
NO
DHW flow rate more than 2.5
l/min.
NO Continuity across DHW 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
neon flashing
Go to section 'E'
NO
neon flashing
NO
Go to section 'F'.
YES
Reduce the DHW flow rate. If
burner does not modulate
NO
clean DHW temperature
sensor and DHW heat
exchanger. If modulation does
not occur go to section 'G'.
Ensure controls are set to
demand and verify the controls
are closed.
NO
External controls and where
NO
fitted, integral timer calling for
heat.
Fan stops.
14.0
Go to section 'L'.
YES
Ensure controls are set to
NO
demand and verify the contacts
are closed.
YES
Is mains water filter and
differential assembly clean?
NO
Replace DHW flow
microswitch.
YES
Replace main PCB
Turn the selector to reset.
If regular resetting is required
YES
or appliance still does not
operate investigation is
necessary.
Go to section 'D'
NO
YES
neon flashing
Go to section 'I' & 'N'.
YES
Go to section 'L'.
YES
Pump continues to
run for 30 seconds.
Fault Finding
YES
DHW flow valve diaphragm
DHW flow valve rod
Go to section 'J' or 'O'.
neons flashing
Turn selector to the reset
position. If the neon does not
extinguish go to sections H and
NO
YES
Operation sequence
correct
Replace diaphragm.
YES
damaged.
NO
obstructed.
K.
Change main PCB.
43