Help please - Pipes vibrating loudly but boiler is off

[neal90125]

I had a Potterton Promax Combi 28HE+ boiler installed in Nov 2011. In Feb 2012 I had a couple of central heating pipes replaced which entailed the system being drained twice. After 2 weeks pipes started vibrating extremely loudly - it sounds like someone drilling through metal and fills the house. The noise starts without warning and comes in pulses i.e. it makes a racket for a few seconds then stops for a few seconds, then it starts again and stops again. Each episode lasts for about 5 minutes in all.

Strangely is this only happens at weekends which could be significant because on Sat/Sun the system is set to come on at 7.30am but 6.30 am Mon-Fri. The noise always happens around 7am. The boiler goes off at 8.30pm every day.

When the boiler comes on it works fine for both heating and hot water although there is an occasional loud bang. All radiators except one have thermostatic valves.

The noise would wake the dead and is driving me mad, and my neighbours with their new baby are not thrilled either. Can anyone suggest what is causing the pipes to vibrate so much when the boiler has been off for hours and what needs to be done to sort it? Thanks.

 

[Dan Robinson]

Were the trv's changed with the boiler?

My first port of call would be those.

 

[Kev F]

As dan said you need a rad without a trv, might need a bypass valve also

 

[buck51]

What makes you think its the heating pipes.

Are you sure it is not from mains cold water pipe?

does it coincide with the toilet being flushed? Or shortly after its flushed.

 

[neal90125]

What makes you think its the heating pipes.

Are you sure it is not from mains cold water pipe?

does it coincide with the toilet being flushed? Or shortly after its flushed.

No it does not coincide with the toilet being flushed or any other use of cold (or hot) water. There was an earlier problem with water hammer when the toilet was flushed but that was a completely different noise/vibration and was resolved with an arrestor.

 

[neal90125]

Were the trv's changed with the boiler?

My first port of call would be those.

No trv's were changed with the boiler but one was added later to replace an old leaking valve. Could this cause such a loud noise even when the central heating has been off for 10 hours+? With apologies for my ignorance....

 

[Dan Robinson]

on Sat/Sun the system is set to come on at 7.30am but 6.30 am Mon-Fri. The noise always happens around 7am. The boiler goes off at 8.30pm

Sorry, was going by this.

Does your controller have optimum start? That would bring the boiler on early and then, yes old TRVs, or TRVs plumbed the wrong way round could cause noies.

Other than that, you need to see what it active at the time.

 

[doitall]

Is there an old motorized valve still connected.

What happens when you set the programmer to the same time every day.

Also try turning the timer off at weekends, and operating the boiler manually.