Baxi 552 Banging

[billyblaze]

I hope this is enough information...brace yourselves....

1. Baxi Bermuda 552 gas boiler

2. After being on for a few minutes, the boiler starts banging and does not stop until both the heating and water is turned off.

3. Recently had new timer clock, new wall thermostat, new boiler thermostat and 2 new electronic valves. I think the pump is about 2 years old and is working. The whole system was re-designed about 2 years ago but was not really used until we moved into the house as it was vacant. The airing cupboard tank was moved from the first floor to the ground floor, level with the boiler. It was perfectly good for about 6 - 8 months.

4. The problem started about a year ago and I've had 3 different gas engineers here to look at the system (one of which changed all the parts above - the timer and digital thermostat on my request), but none of them have wanted to commit to curing the problem, have buggered off and not come back!

5. It happens when the heating is on and the boiler is active. It starts after maybe 5 minutes of activity. Stops when the heating or water is switched off. It seems worse at night and the morning when it is colder and the boiler has to work harder.

6. I have bled the system and even tried the back-fill method to shift any airlocks from the boiler to no avail. I do not think it is an airlock and neither do 2 very competent friends of mine. None of the engineers that have looked at the problem have even mentioned airlocks. I have placed a temperature probe on the heat exchangers within the boiler and they read about 55 Celcius, yet I can take the thermostat out of the heat exchangers and it is cool enough for me to hold it in my hand! The house is warm and hot water is plentiful so it is all functioning ok. The relentless banging is driving me and my family mad yet no-one can seem to cure it.

Please help....

 

[nicknox]

Is it an irregular or regular banging? If its irregular, which I suspect, then you have sludge in your heat exchanger, often worse when the boilers cold or just heating up. Might need a good flush (not always successful) or system silencer added. Or just put up with it

 

[baxpoti]

Very difficult to know with out hearing it.

Only a guess but needs checking........

Flow and returns connected the right way?

 

[HarrogateGas]

Sounds like kettling to me..............

 

[namsag]

Sling some x200 in it or fernox boiler silencer ,as harrogate says sounds like kettling

 

[billyblaze]

Harrogategas:
What do I do to stop it kettling?

Baxpoti
I don't know what you mean, but all was ok for several months and even now works ok, just annoyingly noisy.

Nicknox
What should I flush it with and how do I do it? Is there a way of targeting just the boiler for the flush or do I flush the whole system? How do I go about the system silencer option if the flush is ineffective?

Thank you all...

 

[billyblaze]

Thanks namsag...will try. How do I do it and where do I get it from?

 

[namsag]

Plumb/centre , BQ etc cost no more than 20 quid.

Tie ball valve up start draining system so header tank empties and some more close draincock empty x200 into header tank and un tie ball valve can take a week or so to work but usually notice it straight away very rarely it may need 2 bottles