Technical data

Water diverter
valve not closing. Disconnect
the two pole plug from the
diverter valve coil and run the
boiler in CH mode. Measure the
voltage across the two
connections within the plug,
Is there 25 35 Vdc?
50
FAIL POINT E
No
Yes
Check wiring to
control board. If o.k.
replace control
board.
It is wise to also
replace the diverter
valve coil in case this
was the cause of
board failure.
Choose the appropriate
category below.
Pilot flame only.
Remove ignitor unit from gas
valve. Measure the resistance
across the two outer pins on
the gas valve.
Is resistance between 6kohm
and 9kohm?
All water cold in all
operating modes.
Suspect:
Replace ignitor unit.
Note: It is not possible to reliably check the cross
light performance of the burner.
In the unlikely event of such a fault, investigate flue
problems, burner and injector.
Replace gas valve.
No
Yes
Central heating water
cold or luke warm dur-
ing CH demand.
Suspect:
Measure the resistance of
the diverter valve coil.
Is it 150 250 ohms?
Yes
Replace diverter
valve.
No
Replace coil.
No
Yes
Diverter valve not opening.
Disconnect the 2 way plug
from diverter valve coil.
Does this solve the problem?
Central heating water
hot when no CH
Replace diverter
valve.
Replace control
board.
Suspect:
Check wiring to control
board. If o.k. replace control
board.
It is wise to also replace the
modulating valve in case this
was the cause of board
failure.
No
Yes
Modulating valve
not opening.
Create a DHW demand and
fully open a tap. Measure the
voltage across the two tags on
the modulating gas valve.
Is it over 10Vdc?
Luke warm temperatures
in all operating modes.
Suspect:
Replace gas valve.
Scaled / inefficient
water / water heat
exchanger.
Replace.
Low DHW outlet
temperature in DHW
mode.
Suspect: