Baxi Bermuda Inset BS/TS Problem

[andrew1210]

Hi, this 'problem' has been happening for years but I have decided to get it seen to....

My gran has a Baxi Bermuda Inset BS/TS BBU and the pipes seen to 'bang' loudly when the CH is on.

Decided to do a bit of Inspector Clueso tonight...

When there is a demand for heat from the room thermostat, the pump kicks in and the boiler will fire in quick succession. However when the demand is satisfied, and you hear the thermostat 'click' off the pump immediately stops but the boiler burner remains on. After a few seconds, the pipes from the boiler begin to 'bang' loudly, echoing throughout the system then the boiler will shut off after around ten seconds and the noise will gradually fade away.

I assume this is happening because the pump is shutting off but not the burner, thus not taking heat away form the boiler, maybe an overheat stat. or something is cutting the burner off. When the banging is happening just after the burner shuts off, you can immediately silence it by turning the room stat. up, kicking the pump to life and taking the heat away form the boiler.

Is this boiler meant to work like this, or is there supposed to be a pump overrun, as the pump is certainly not overrunning?

 

[gas4you]

No it is not supposed to be like this.

Sounds like the pump is wired to the stat on its own.

The wiring will need to be checked and changed to make the boiler go off at the same time as the pump.

There is no pump over run with these boilers.

 

[andrew1210]

OK, thank you, is it causing the boiler any harm being this way?

It has been ok since installation in 1999 and not turned up anything wrong at services etc. so i'm not too worried about it but will get it looked at soon

 

[gas4you]

There is an outside chance that the overheating and banging could damage the heat exchanger, even a hairline crack in the extreme.

I would suggest you get it checked asap for your own piece of mind.

 

[andrew1210]

Hi, I know its been a while, but got a plumber out last week, hes coming on Monday night to sort it, agreeing that it is a wiring issue that has been there form install.

 

[andrew1210]

Hi, It's been a very long while now, but finally got the plumber to come back and sort it.

It turned out to be the boilers internal thermostat that has lost calibration and a new part is ordered and on it's way. It was deffinately out of calibration as he noticed, even when set at 'low' the radiators were still getting hot.

It's been left at minimum just now and is giving adaquet heat until the part is obtained and the banging has stopped at now at this lower temperature

Also got the fire cleaned and hoovered out at the same time so now have a nice clean burning, blue flame