Noisy Central Heating system

Hi there,

Been trying to solve this problem of ours for about a month now with no success, it's been driving us up the wall. I'm hoping some kind soul here can point us in the right direction. Got absolutely zero experience with plumbing but will try to explain as best I can ....

We got a new Combi boiler installed about 4 months ago (Vokera Compact HE combi boiler), at the same time 3 of the 6 radiators we have also got replaced. The new radiators each have a TRV fitted while the older ones just had the traditional valve. It was all going great until about a month ago, I noticed the pressure was a little low (about 0.8 bar when cold) so topped it up to 1 bar. Ever since then whenever the CH is on there is an intermittent & reasonably loud (wakes us up each night several times) shuddering noise and vibration throughout the entire CH system. It's not just the one radiator or boiler, so I can't pin it down to 1 location.

If we run the hot water the noise goes away for a short period of time. Same for if we adjust the TRV on one of the new radiators. But it soon comes back.

I've bled all the radiators many times over and can't see any air coming out of them now. There was quite a bit of air came out at the start. There doesn't seem to be any loss of pressure indicating a leak, but over the last month I have bled the radiators a lot of times and each time air (a little at least) does seem to be coming out.

I don't know for sure if me topping up the system was a factor in it but seems like a heck of a coincidence. It's also about the same time the weather started getting cold and we had the heating on more often. We tried draining the system down to about 0.8 bar again, in case it was a pressure issue, but the problem still remains.

Tried to call the engineer who fitted it but he isn't answering his phone or returning voicemails . We had to call him back the day after he fitted it as one of the pipes was leaking and he used some sort of plaster to hold the tap heads in place since he broke the fittings (i replaced them myself later). All in all not impressed by our choice of engineer but not much can do about that now.

Can anyone help us get a good nights sleep and suggest what could be causing this? At least if we have an idea of the problem maybe it'll be easier to talk to a plumber if we find one.

Thanks!

Are you able to indentify the flow and the return on your new rads?

If so, has the new TRVs been fitted on the flow or the return?

It's quite common, you can get a bi-directional TRV which can be put on either the flow or the return (obv better on the flow as it's uniform). But cheaper But TRVs that are not bi-directional are still readily available, and if they are put on the return then the water is traveling through the valve the wrong way, which causes a kind of humming vibrating noise, and when you turn the TRV it will stop.

Thanks, I'll see if I can identify the flow and what side the TRV's are on. Not sure if this would be the cause in this case though (?), the noise is also temporarily resolved by running the hot water and the system ran well for about 3 months before this problem started.

It seems to only be a problem once the system has heated up, starting it from cold it goes fine for a bit. Then the vibrating noise comes intermittently when it's warmed up, thermostat is about 20-25 degrees Celsius. I tried dropping it to 20 from 25 to see if it reduced the noise but had no apparent effect.