Banging noise in central heating system

[Madrab]

Well I think 90% probability that your TRV's are the issue.

As @ianmcd suggests, the more slapdash installers can swap the flow and returns about all the time and then sometimes the customer is left with banging valves. Even though they are 2 way valves, all the years they have been running a certain way and now if it's switched a couple of the valve's aren't happy.

Of course, not being there then hard to be absolutely sure but when the banging occurs you should also be able to feel it on the body of the valve.

 

[RK_London]

Apologies for my ignorance but how installers swap the flow and return? I will check the body of the trvs for vibration when banging occurs. Thanks

 

[ianmcd]

when the banging starts tirn the valves on the noisy rads down to close them , if they stop banging you have answered your own question

 

[ianmcd]

Apologies for my ignorance but how installers swap the flow and return? I will check the body of the trvs for vibration when banging occurs. Thanks

All boilers have a flow and a return pipe, but some are flow on the left some are flow on the right, far too many installers just join the easiest route and dont care which is which

 

[RK_London]

thanks

 

[Harry Bloomfield]

it could be that when they fitted the new boiler they have reversed the flow and return, happens all the time

Good grief, that's what you get trusting a pro

 

[ianmcd]

Good grief, that's what you get trusting a pro

sadly it is a lot more common than you would think

 

[Harry Bloomfield]

All boilers have a flow and a return pipe, but some are flow on the left some are flow on the right, far too many installers just join the easiest route and dont care which is which

Glad to say, I marked mine up so there could be no errors.

 

[RK_London]

Is it true to say the flow side of a radiator is always hotter than the return?

 

[Harry Bloomfield]

Is it true to say the flow side of a radiator is always hotter than the return?

Yes - common sense really. Best time to check and mark the flow side, is with the system from cold, when the heating first goes on - when temperature difference between flow and return is greatest.

 

[RK_London]

I switched off the nosier radiators overnight near bedroom and finally got a decent nights sleep.

I've checked the radiators with a thermometer and (for most of the radiators) the Lockshield pipe is the higher temperature flow and valve is the return.

There is one radiator in hallway where the flow is the valve although this isn't a TRV.
There are also two other radiators where the TRV temp is afew degrees higher than the lockshield side - maybe a balancing issue. I also noticed one of the noisier radiators (which was switched off) in bathroom isn't a TRV but regular valve ( pic


So overall looks like the flows may have been swapped as suggested by Ianmcd although not sure why there are a few radiators connected right way.

 

[Harry Bloomfield]

So overall looks like the flows may have been swapped as suggested by Ianmcd although not sure why there are a few radiators connected right way.

You need to get the installer back and insist (s)he swaps the pipes over to work in the correct orientation. As someone above suggested, bi-directional TRV's become used to working with the flow direction they are installed with, so no problems until someone comes along and reverses the flow direction.

My own heat only boiler has had to have a pipe cross over above it, due to the last change of boiler using the opposite pipe layout to the previous one.

 

[RK_London]

I've contacted the installer and waiting to see what he says

 

[Madrab]

The concern here though is that the installer didn't know to check this, it's system fault finding 1'o'1. If the rads/pipes start to bang when a new system has been installed then the valves would be the first thing to check.

That being said you do have to give them the opportunity to sort it and if they cant then they would need to pay to get it sorted by someone that knows what they're are doing.

The banging certainly wouldn't be sorted by adjusting the power setting and if anything you would turn the pump down not up.

You certainly shouldn't have to live with it though.

 

[RK_London]

I agree - I am concerned the installer didn't do the obvious checks despite having credentials and recommendations. I will give him the chance to put it right but my confidence is not high.

On your point about the pump setting, I agree. It made no sense to me to put the pump speed higher so I turned it back down - it was too noisy and didn't solve anything.

I also have a separate random banging noise in a room close to boiler ( attached below) - not sure if it's connected but will ask to get Vaillant engineer out. Want to get pipe flow problem sorted first.

****
you can insert pics by copy and paste or in "more options"
mod
****

I'd like to thank everyone on this website - you've all been incredibly helpful and I will keep you updated with progress