Banging boiler

stuartinlancashire · 28 May 2008

My girlfriend has a problem with her central heating boiler banging. It's a Baxi boiler, I'm not sure of the exact model but its about 20 years old.

Anyway shes got the system on hot water only at the moment and it starts to bang when it's been on for a while and the banging appears to be coming from the boiler but it ressonates around the house via the hot water pipes. We are guessing the problem is with the water heating rather than the CH as it does it with the CH off.

I'm guessing this is likely to be caused by an air lock somewhere in the hot water system but any opinions and suggestions would be welcome.

twgas · 28 May 2008

check there is some water in f&e tank

is pump working

can you bleed pump or pipes near cylinder

does the tank get hot before the banging starts

JohnD · 28 May 2008

when the boiler comes up to temp, does it go "bonkety bonkety bonk bonk bonk"? and carry on until 5 - 10 secs after the burner shuts down?

is it a hard water area?

how often do the rads need bleeding, and what colour is the water that comes out?

SortedPlumbing · 28 May 2008

Check the feeder tank in loft to make sure it is full of water...(to make sure float valve isnt jammed)

Sounds like a possible pump......ie water not circulating

stuartinlancashire · 28 May 2008

Thanks all for your prompt replies, I've just realised I asked about this last year, I'm guessing we cured it somehow but it's started again!

Agile · 28 May 2008

Try turning the boiler thermostat know down a bit.

All that bonking is not going to do it much good at that age!

Tony

stuartinlancashire · 28 May 2008

JohnD said:
when the boiler comes up to temp, does it go "bonkety bonkety bonk bonk bonk"? and carry on until 5 - 10 secs after the burner shuts down?

Yes that sounds like what it does

JohnD said:
is it a hard water area?

No

JohnD said:
how often do the rads need bleeding, and what colour is the water that comes out?

I had to bleed one a while back but I couldn't tell you the colour of the water I'm affraid and they don't have to be done regularly.

Agile · 28 May 2008

Try turning the boiler thermostat knob down a bit.

All that bonking is not going to do it much good at that age!

Tony

stuartinlancashire · 28 May 2008

Agile said:
Try turning the boiler thermostat knob down a bit.

All that bonking is not going to do it much good at that age!

Tony

I've thought of that, but I can't find a thermostat

At my parents house the thermostat is a dial type thing on the cylinder but gf does not have one on hers that I can find.

Agile · 28 May 2008

All Baxi boilers have a thermostat knob on the front, perhaps behind a flap or sliding door!

Turn it down about a quarter!

Tony

twgas · 29 May 2008

is it a back boiler (behind a fire) if so the thermostat will be behind a flap beneath fire.

namsag · 29 May 2008

When it starts banging (prob about half hour after water only on) go in loft and there will be water shooting out of vent pipe .
Your boiler stat will have gone and needs changing

PREMIEREFC · 1 Jun 2008

I have just rejoined the web site. I have the same problem with mine it is a vented system. the hot water is filling the header tank and then out through the overflow. is the thermostat the one on the emersion tank or is there another one on the boiler

gremlin16 · 1 Jun 2008

Watched a documentary last week about banging cars, they called it mechanophilia, think it extends to other metal objects, such as banging boilers.

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Banging boiler

namsag

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