Boiler banging after turning off

[reprised]

Hi all,

We had a new boiler installed by British Gas in November last year and it's been ok so far up until a couple of days ago when it started banging when the heating switches off. The heating and water heat up fine but about 10 seconds after the boiler turns off (either manually or on thermostat) the banging starts and lasts about 15 to 20 seconds. The BG Precision boiler is installed in the loft with hot water cylinder and pump in airing cupboard. We have had BG out as we have a service contract but they didnt find a problem (my Mum was here when the engineer came) but the noise is loud and sounds like somethimg is going to explode. We have called them again to have a look but is it safe to use the heating? There are no other noises whilst the boiler is actually running. Does anyone have any suggestions as to what causes this noise?

Thanks for your help

 

[hammers4spanner]

possible pump over run issue maybe by pass

 

[plumber0808]

Phone bg back, get ready for the powerflush hard sell.
remind them it should of been done when the boiler was installed.

 

[gassafe]

I would also guess a pump overrun issue. Does the pump continue to run after the boiler has switched off?

Sounds like the excess heat remaining in the heat exchanger is boiling the water!

 

[reprised]

I would also guess a pump overrun issue. Does the pump continue to run after the boiler has switched off? Sounds like the excess heat remaining in the heat exchanger is boiling the water!

The pump switches off with the boiler - i think it has always been that way since it was installed. Should it still run then after the boiler has shut off? We had the system powerflushed and had filters installed as part of the install so if they do say that then it should be free.

 

[gassafe]

If you give us the boiler make & model someone on here can tell you If it needs an overrun!

 

[gassafe]

The pump switches off with the boiler - i think it has always been that way since it was installed. Should it still run then after the boiler has shut off? We had the system powerflushed and had filters installed as part of the install so if they do say that then it should be free.

Just because it was installed that way does not mean its right! This is British gas after all!

 

[Roger Welton]

Most boilers require a pump overun to get rid off excess heat from the boiler on shut down, if not connected or the pump has nowhere to diapate this heat (no bypass) you can get the symptoms you describe.

Edit to add: Get BG back, they installed it they need to fix it.

 

[hammers4spanner]

I personally would kick up a right song and dance about it as cant imagine the boiler change was much less than a fair overpriced sum .

 

[Dotty]

Definitely call bg back in.

 

[reprised]

If you give us the boiler make & model someone on here can tell you If it needs an overrun!

it is a BG Potterton Precision boiler. BG are due to come tomorrow - just thought i'd get an idea of what it may be, hopefully they can sort it out.

 

[Dotty]

I'm afraid all you'll get out of us is you have a noisy boiler and you need to have it looked at. We won't go into the technicalities for your own safety.