Domestic Boiler noises (cavitation)...any expertise?

[Fab Foodie]

Morning..

A while back came home to find the boiler (Glow-worm 18hxi High efficiency Condensing boiler) banging away like a good-un.
Couldn't feel the water pump running so made rash assumption that pump had failed (It's pretty old). Turned-off boiler and heating system and ran the Immersion heater for hot water. It's been off for a few weeks now.
So, today, trying to figure out what's up.
Check all the electrics etc. and found that the pump seems OK (Runs only when the boiler is powered-up apparently) and controls still work, however whn turning the boiler thermostst up enough to light the flame it soon starts cavitating.
The boiler is probably 3 years old (not serviced in that time ) and has run fine up until now.

Before I call an engineer out, anybody any suggestions?

Right now I've got water circulating, so the pump runs. Guess air might be the issue. Will see If I can bleed anything.

 

[sheddy]

Do you have a header tank ? If so is the ballcock working OK ?

 

[jasper]

It may be air in the system. Be careful if you're bleeding a pressurised system though.

 

[Globalti]

Don't ask on here, go and ask on DIYnot.com

 

[Fab Foodie]

Don't ask on here, go and ask on DIYnot.com

Good call RR, had not seen this before.

So far I think it's OK, mostly air in the system, I heated all the water gently during the day and the problem seems to have dissappeared for now.
Am gonna get some Fernox and add to the water anyhow.

Cheers
FF->.

 

[Over The Hill]

Hi

You got my attention with you coming home to find the old boiler banging away!

So to the problem..
Problably air, so bleed it out if you can, sometimes it will go on its own (a good system has a bit where it will pass up to the vent). It could have some crud in there that is blocking it and thumping about.

Question arises - why have the boiler on -it is August! Yes I know it is not the hottest on record but my boiler has not been on since May.

If you are using the boiler to only heat the hot water then that may be the root of the problem. You have a big fat boiler with enough go in it to heat the whole house, you are starting it up and running it to heat a tank of water. Burning fuel -- heat water in a pipe -- which heats water in the tank. The transfer of heat may be not as good as the production of heat so the boiler may be going into some sort of shut down where one bit is getting too hot. Immersion heater is more efficient at delivering heat at the point of need.

It is worth getting the thing serviced so that it runs properly. A badly set up boiler can burn up more fuel as well as kill you. I have a boiler woman who comes around and cleans out my pipes every now and again.