Gas smell from boiler when it switches off.

[Restoration man]

Ok cheers. There goes another £200. Sniff sniff.

 

[Agile]

The gas valves have a rubber faced plunger which is pushed against a seal by a spring when the valve is off.

They usually seal effectively but if there is any leak its a very small one.

BUT modern gas valves have TWO internal valves in series so both would have to be leaking!

It is pretty rare for them to leak nowadays.

 

[Belboz]

Sniff sniff.

That's the problem............

 

[nortonj]

I would do as @Steelmasons suggested.
Wait till boiler switches off after heating.
Turn gas cock under boiler off.
Return ten mins later when the smell has been appearing.
If it still smells of gas then its not an appliance fault. The smell is coming from elsewhere.

 

[Restoration man]

I don't agree with that Nortonj. If you've turned off the gas stop cock and still smell the gas it could be gas in the boiler casing slowly leaking into the room.

 

[nortonj]

Just try it. What have you got to lose.
Your suggesting no smell when the burner is lit so as soon as the burner is extinguished turn the gas off to the appliance. If you smell gas in 20 mins time then cant be the appliance

 

[Restoration man]

Earlier today SGN the mains people tested from the meter into the house and confirmed it was a rock solid test. This is against the closed cooker hob valves and closed electronic gas valve in the boiler as the gas tap under the boiler was open as normal.

This means the electronic gas valve tested ok at that moment in time.

The gas valve is the only moving variable that could be sealing and not sealing.

Service eng is due at 4.30. Will advise after.

Thanks

 

[Jackrae]

Unless it is the control board giving the gas valve a short open signal immediately after the post-purge phase. Since fan is at rest any gas blown off will accumulate within the casing.

 

[PullerGas]

Unless it is the control board giving the gas valve a short open signal immediately after the post-purge phase. Since fan is at rest any gas blown off will accumulate within the casing.

Good call mate. So shutting the gas cock would not confirm that fault.
But the 'engineer' could use a Sniffer after the post-purge.

 

[ianmcd]

just shut the gas valve while the boiler is running , the boiler will sense that and will shut down and if you still smell gas then it has nothing to do with your boiler but you have changed your story so many times so doubt if you will do what you have been told on more than one occasion what to do

 

[Steelmasons]

As said he's an attention seeker.
I have a nose for BS...

 

[Steelmasons]

I don't agree with that Nortonj. If you've turned off the gas stop cock and still smell the gas it could be gas in the boiler casing slowly leaking into the room.

Turn off appliance isolation valve which is located on underside of boiler..

 

[Steelmasons]

Unless it is the control board giving the gas valve a short open signal immediately after the post-purge phase. Since fan is at rest any gas blown off will accumulate within the casing.

This boiler utilises a zero governor (premix)......combustion fan RPM controls gas input to burner , with fan @ rest the servo diaphragm will remain closed and hence weep line pressure will be zero (no gas).

 

[PullerGas]

Turn off appliance isolation valve which is located on underside of boiler..

As one who's a stickler for correct terminology Steely, are you referring to the Gas cock?? Just to clarify, same Hymn Sheet & all that dear boy.

 

[PullerGas]

This boiler utilises a zero governor (premix)......combustion fan RPM controls gas input to burner , with fan @ rest the servo diaphragm will remain closed and hence weep line pressure will be zero (no gas).

While yes that's the basics of it, but who's to say there's not a fu.ked relay or transistor on the PCB??

BS or not he's quite bright for a Bonnybrig Benny!!