11
f-
.~
Does appliance modulate
down to low fire (ignition
rate) and go off?
To test
Put appliance thermostat to
no. 6, fire appliance for
central heating. Burner
should now modulate down
and shut off at approx 60°C
(see temperature gauge).
~
YES
If COMBlcompact VCW
Go to 8
If THERMOcompact VC
End of job
~
&
For VCW only - is D.HW
operation OK?
::i
YES
+
End ofjob
tiJVaillant
NO"
NO"
I
HEATING, CONTROLS,HOTWATER.
~
(a) Test NTC/Electronic
board.
Pull off NTC wire (from
DHW overheat) and touch it
on chassis, if burner goes
off change NTC.
Refer to Pic 29
If burner stays on change
electronic board.
(The gas operator may be
stuck open e.g. debris.
This symptom is very
unlikely but can be checked
by pulling off the wire to the
operator. If burner remains
alight then change
operator).
(a) Check demand for hot
water - tap open and supply
pipes correct way round.
(b) Check water section
moves servo valve
cam - if not check
venturi/diaphragm of water
section. Refer to Pic3().
(c) Check microswitch M3
(20v DC). Refer to Pic 31.
(d) Check hydraulic diverter
valve moves right opening
microswitch M1 (with M1
open no electrical continuity
through switch). Refer to
Pic 32.
(e) If DHW not hot enough
check gas supply working
pressure at appliance inlet
& burner pressure. Refer to
Pic 25 & Pic 28.
(f) If water flow rate
insufficient check. for
adequate cold water main
supply and/or blockage in
water section or DHW heat
exchanger.
End of job.
13
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