Boiler flame jumping/thumping.

[Ian_m]

Was at a friends house at the weekend and noticed that their boiler in the kicthen was "thumping" slightly.

Peering through the window, nice blue flames, but sometimes "wavering/moving up" causing the slight thump as the flames jump back to the burners. Issue may have been worse on flames out of sight of inspection glass. Boiler was fitted 2002 odd.

They did have an issue about a year ago, where after having it serviced the outdoor vent fell off, but the servicing guy returned to sort that.

My thoughts were exhaust fumes getting into the air intake (especially as they mentioned issue with outdoor vent) or air leak in the side of the cabinet allowing air to be drawin in or heat exchanger dripping water (though nothing leaked yet) ?

If he can fix it themself he would like to, though I did suggest he look at the vent again to see if fallen off/broken.

[Ed Sirett]

This is not right. If you could describe the 'outdoor vent' that would help. Make and model would be a bit helpful too.

[sponix]

For one moment I thought you were peering out through the kitchen window and saw flames!

Possible. Worth checking the vent is fitted correctly before going any further. Also check the fga A ports in the flue are sealed.

There's also something in the back of my mind saying "gas regulation". Perhaps the gas control module/valve is faulty or has dirty contacts and causing a fluctuating flow of gas to the burner?

I doubt it's due to dirty jets as the boiler was serviced only a year ago.

sponix

[Ian Middleton]

It was an Ideal make, wall mounted non-condensing boiler. Air in + vent is via concentric vent, via kitchen wall to triangular/circular metal external vent. I looked but didn't touch as alcohol and DIY and even alcohol and gas repairs do not go well.

The thumping is not loud, my mate had never noticed it, just thought it was normal boiler noise.

Actually as I typed, he phoned, had it sorted, it was a crack/tear in a flue pressure sensor pipe and or sensor causing gas valve to chatter on and off. His "man" sorted it and iit no monger thumps,

[Owain]

Oh good, must be terrible having a thumping monger.

Owain

[Sponix]

My m8 got thumped by a monger once.

sponix