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The potential for the printed circuit board /gas valve failure does exist and therefore testing
the gas valve soundness after the boiler shuts down should be checked as a matter of
routine.
Printed circuit boards that have locked with fault 9 can be reused once the software has
been re- booted. Please contact our technical helpline for details
2. Gas Valve Control Circuit Failure
Fault 9 may also be the result of the P.C.B. detecting an ionization signal indicating that
that a flame is still present at the burner after the demand for heat / hot water has finished.
Normally the main burner extinguishes the instant the gas valve closes.
If however, the ionization signal can still be detected 5 seconds after the gas valve relays
have closed then a second attempt will be made to close the gas valve relays. If this fails
the boiler will lock out in a safe mode fault 9.
In this safe mode of F9 the boiler will continue to run the fan to avoid the possibility of gas
build up within the boiler. It is not possible to stop the fan running by switching off the
boiler by the control panel. Only by isolating the boiler from the mains electrical supply will
the fan stop running. Also if the boiler is in F9 then it is not possible to reset the lockout by
the control panel. The P.C.B. must be replaced or the software within the board must be
reset by using an “Autotest Unit”.
POSSIBLE CAUSES
PCB failure (electro-valve relay broken)
Gas valve failure
Residual Ionisation Signal
FAULT 10
Domestic Hot Water Thermistor Failure – Screw in Type
5 seconds – ten 1 second flashes - 5 seconds
This occurs when the values for the safe operation of the domestic hot water
thermistor are out of range for more than 10 seconds during demand for domestic
hot water. This 10 second delay is to allow for water drawn during central heating mode to
stabilise. After more than 10 seconds lock out will occur.
Reset is automatic once the thermistor values return to operational values or the faulty
thermistor is replaced.
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