Gas boiler knocking!

tony glenn

I came downstairs this morning and heard a steady knocking noise from the utility room.
It was coming from the gas CH boiler on the wall.
Just a steady regular knocking, like someone lightly tapping a pipe with a hammer.
The boiler hasn't been used for two months (as it's Summer ha!), and the noise stopped when I switched off the mains switch on the wall.
The boiler fired up ok, although I didn't run it for more than 30 seconds in case of problems.
The knocking continued whilst the boiler was working btw.
Any ideas what the cause of the noise might be?

Phil.x

Limescale or air in the heat exchanger.

tony glenn

Thanks for the tip.ðŸ‘

Dtp1979

tony glenn wrote: »

Thanks for the tip.ðŸ‘

Highly unlikely it’s limescale or air.
Probably a chance it’s a sludge buildup or more than likely the pump is seazed from lack of use. Happens a lot. Very simple to fix but if the pump is inside the boiler then you need an Rgi to sort it

tony glenn

Dtp1979 wrote: »

Highly unlikely it’s limescale or air.
Probably a chance it’s a sludge buildup or more than likely the pump is seazed from lack of use. Happens a lot. Very simple to fix but if the pump is inside the boiler then you need an Rgi to sort it

I think you're right, better safe than sorry. I have a regular RGI who does our annual service I'll take out a second mortgage then give him a call..... thanks!

Dtp1979

tony glenn wrote: »

I think you're right, better safe than sorry. I have a regular RGI who does our annual service I'll take out a second mortgage then give him a call..... thanks!

If it’s a seized pump then it’s a 2 min job.

tony glenn

Dtp1979 wrote: »

If it’s a seized pump then it’s a 2 min job.

It was the Zone Control Unit, nothing to do with the boiler after all.