What is causing the Loud Bang in my plumbing/heating system

[Tired1]

Hi , Hoping someone may have an idea what this could be...
For a good few months and particularly (but not always) in the middle of the night, we assume that as the hot water kicks in on the central heating we can hear what sounds like a pipe shuddering somewhere in the house, there is then a really loud bang and we then hear the kettling of the boiler as the hot water starts warming up. It does not do this all of the time but perhaps 3-4 times a week and rarely more than once a day. For info we have a Powermax 155 Boiler. British Gas have looked a few times, changed the electrodes as they first thought it could be a gas ignition problem and have since been back and said they are out of ideas. The last BG engineer (today) tested the CH system again and suggested the boiler system is working fine. He assumed it may be water hammer, but then ruled that out as it happens in the night when no taps etc are running. All the radiators work really well so he said he didn't think it was trapped air, and so his last suggestion was a radiator valve fitted the wrong way, (but could not find one) or a loose water pipe that is banging another when the water runs through it. He then packed up and said he couldn't help further. Sods law it never happens when you need it too.

If anyone else has experience this any suggestions would be great as I need my sleep and don't know what to do next.

 

[45yearsagasman]

Set the programmer to OFF when you are sleeping. Have it come on 30 mins before you get up would be my advice. Noises are very difficult to diagnose without being on site. Worked on loads of Powermax and mostly they were always quiet, although a few suffered from explosive ignition.

 

[Tired1]

Hi, I appreciate your advice and I have turned it off before now, unfortunately this is not solving the problem though, just ignoring it. As I said the BG Engineer replaced the electrodes? to rule out explosive ignition so they don't put it down to that. The other point is that it's not just general continuous taping and clunking, it is a one off loud bang.

 

[Agile]

Is it always at the same time?

Does it happen if power is cut to boiler?

Does it happen if the gas to house is turned off?

Tony

 

[Tired1]

Hi Agile

No it doesn't happen always at the same time, it can be any time of the day, its just that recently it tends to be later in the evening or at night. This is the problem it is unpredictable so I haven't been able to stand around in different places to pinpoint the exact source. We just assume it is the boiler because of the fact the kettling always follows the bang.

Have never tried turning the gas off to the house so I don't know ( I'm not that keen to mess myself) and as far as I know it doesn't happen if the boiler is off . It does happen though if the CH part of the system is off (i.e. in Summer) but the hot water is set to on.

I'm no CH engineer however so this next bit may be me misunderstanding how my system works. However if I turn the thermostat on at the wall the CH comes on and is pretty quiet , the rads warm up nice and all is ok. Most of the time the kettling then starts later which I can live with and I presume is when the hot water warming up? ( Simply because when the CH is off and HW is on the kettling still happens). The only time the bang occurs is right before the kettling starts, but not always.

 

[Nige F]

Hi , Hoping someone may have an idea what this could be...
For a good few months and particularly (but not always) in the middle of the night, we assume that as the hot water kicks in on the central heating we can hear what sounds like a pipe shuddering somewhere in the house, there is then a really loud bang .

Could well be a pipe trapped somewhere like in a notch through a joist - I`ve heard and remedied this before . I can make no comments about boilers , as I didn`t keep up with their development or get Gas Safe registered . But pipes can certainly get trapped as they expand , then force out of the pinch point suddenly

 

[Tired1]

Thanks Nigel. I am hoping that at some point I will be near the boiler cupboard when the noise happens that way I can hopefully assess whether it is the boiler or a pipe.

I appreciate everyone's advice. Many Thanks