Noisy central heating + balancing

[Paul Stansfield]

Hi folks,

I've been trawling through the group(s) for information about my problem, and while I've got several ideas on how to proceed, I thought I'd ask a couple of other questions.

A brief background: Bought a 25 year old house back in November that had been vacant for around 10 months. After bleeding the rads and the vent pipe by the cylinder, CH and hot water worked ok. The only problem that developed over a week or so was a nasty whine from the boiler as it heated up. Kettling - I assumed.

So, down to Homebase I went and bought their own-brand CH cleaner and inhibitor. Flushed it out after a couple of days, added the inhibitor and fired it all up again, and it was not any different. In fact, it seemed to get worse as time went on.

So, down to Homebase again, and I bought a tube of the Fernox superconcentrate cleaner, injected it and left it for two weeks. As soon as the following day, the boiler was perfect - no whine, no vibration and CH seemed to work. Anyway, after two weeks - it was time to flush it out. Kept on flushing until the water runs clear, added Fernox inhibitor to the tank and bled the system.

Anyway - immediately, the noise returned, although now it's not a whine, it a low frequency drone which vibrates through the floor (and of course, wakes me up the moment the boiler fires). The drone starts as soon as the boiler starts, lasts for about a minute and then fades away. When the boiler stops and starts again, the problem returns. Which brings me on to the next question....

Knowing that the rads were all out of balance, I decided to follow the excellent advice in the FAQ and balance them all. It seems successful, but when the CH is running, the boiler stops and starts every couple of minutes (presumably, because it can't heat the water any more). Is this normal, or have I been a bit to conservative on balancing the rads, and too much residual hot water is returning to the return circuit back to the boiler? If so, is it just a question of closing the lockshield valves a bit more?

Thanks in advance,

Paul

[Andrew Gabriel]

Could it be the pump vibrating?

It's normal once the system is up to temperature, assuming a non-modulating boiler.

You should set the flow so there's a drop of about 10C across each radiator at a flow temperature of 80C (or for a condensing boiler, a 20C drop at a flow temperature of 70C), unless you know the system was designed for different values. If one of the radiators is also the bypass loop (no TRV or hand operated valve), be careful not to close that one down too much or the boiler could end up with unsufficient bypass flow -- sometimes you have to compromise with a reduced temperature drop on a bypass radiator.

[Paul Stansfield]

Hi Andrew,

Sorry no, definately not the pump - that seems happy spinning away at a constant RPM (and it's upstairs in the airing cupboard). I guess it's still kettling, although I thought that created banging and clonking rather than whining and groaning! As the days go on, it appears to be getting worse. I just find it a little strange that putting Fernox cleaner (not inhibitor) originally solved the problem. I wonder if the boiler silencer would do the trick?

The only weirdness I can find on the system is that every rad has a TRV, and the rad nearest the thermostat I open the TRV to maximum so it doesn't interfere with the stat.

Thanks,

Paul

Andrew Gabriel wrote:

[Aidan]

Fanned flue boiler with a defective fan bearing?

[Paul Stansfield]

Hi Aiden,

No fan on the flue. The only thing I haven't found is if there's a bleed valve near the heat exchanger in the boiler which has been mentioned in other posts, so that's a possibility I can look at. It just seems really odd to me that Fernox cleaner stopped the noise - that makes me doubt whether it's kettling.

[Phil Addison]

TRV valve vibrating? can happen if worn/clogged or if fitted with flow in wrong direction. Some have arrows to indicate required flow.

Phil The uk.d-i-y FAQ is at

Google uk.d-i-y archive is at NOSPAM from address to email me

[Paul Stansfield]

TRV's are fitted correctly although one or two don't work. I've added Fernox boiler silencer as a last resort and I'm pleasantly surprised it's worked to some degree. The droning noise went back to a whine, and then stopped completely over an hour or so. It still groans and rattles pipework when it shuts down, but it's much more tolerable than before.

I'm still not convinced the system is particularly healthy, but the previous owner(s) of the system obviously abused it and I'm sure it's better than it was. I do wonder whether another course of Fernox restorer would be worth a go to clear what I guess is scale in the boiler, but as long as it's quiet, I'll put up with it until I replace it.

Cheers to everybody for their suggestions.

Paul