Central heating 'vibrating'

[Jason Judge]

We' ve recently replaced an aging Gloworm cast-iron boiler with an Ideal Response 120 combi. It works fine, apart from some noises.

Most of the radiators are fitted with thermostatic valves (only one radiator is not). When a valve upstairs is on the point of closing, it seems to set up a horrendous vibrating noise, that can be felt and heard through the whole house, but loudest at the value. If I switch the value up or down a little, so it is fully on or off, the vibrating stops.

The vibration seems to resonate around 20 to 30Hz - but that's just an estimate - it is very loud though. It happens on several of the valves, but not all.

We don't have any cold spots or radiators that don't heat up. We also never had this problem on the old boiler (though it did sound like a giant kettle boiling and thumping around). Switching on a hot tap stops the vibration, for as long as it is on. I have no idea why that should be, as the taps and radiators should be independant.

I was just wondering what the problem could be, and how I could go about confirming and/or fixing it.

Thanks,

-- Jason (newbie here)

[John_ZIZinvalid]

What have setting do you have on the non-thermostatic radiator, this sounds to me as if the system is overheating. Some Combi's have a pump over-run which allows any excess heat to be removed from the boiler and into the system, you old cast iron boiler wouldn't have needed such a thing, the designers allowed for the excess heat.

J

[Andrew Gabriel]

This happens when valves are installed with the water passing through in the wrong direction. Many valves are bi-directional nowadays, but if yours isn't (should be an arrow on the valve body), then it wants moving to the other end of the radiator or turning round the other way (so the body is horizontal if it's currently vertical), if the valve connections are reversible for such mounting.

Another thought -- maybe the pump's dynamic pressure is rather high. You haven't shut off the radiator with no TRV have you? It might also be that the pump could be turned down a notch, but that should really only be done if you can check the flow through the boiler is still adequate.

[Jason Judge]

I set the heating temperature (on the boiler) down to its minimum, but the radiators still get fairly hot - perhaps the thermostat in the boiler is not working?

The non-thermostat radiator was down fairly low. I've turned that up now, to see if it makes a difference. That radiator also happens to be very close to the boiler (which is why I think it was low). I'm not sure if that makes any difference - I guess it can still lose roughly the same amount of heat, regardless of whether it is next to the boiler or at the other end of the house, assuming the pipes are well lagged. But I can change that if you think it would help.

The cooling offered by switching on a hot tap makes sense now. Thanks.

-- JJ

[Rusty]

Had this problem with a builder (but a grotty plumber) who put the thermostatic valves on at random and some have the water flow the wrong way. Previous posts here indicate that some valves work both ways round, some don't and vibrate causing the pipes to transmit the sound round the house.

rusty.

[Jason Judge]

Possibly it is a combination of the two: some valves have been fitted backwards, and the new pump is more powerful, triggering a vibration that was not a problem before. I thought that perhaps the new boiler had been fitted the wrong way around, but it does flow the same way as the old pump. It's all a bit of a mystery how so many of the TRVs are fitted backwards - I think a weekend job draining and refitting is in order ;-)

Thanks for the tips.

-- JJ

[Jason Judge]

Yes - I have identified three of the valves fitted the wrong way around - and all vibrate now when on the point of turning on or off. They sound like four hefty builders hitting a radiator with a pick-axe handle each. I'll leave these off until I get a chance to reverse them.

Thanks for the info. This has given me a good excuse to read the service manual for the boiler, at least. Lots of interesting tips on balancing and the reasons for at least one radiator without TRVs (and tells me that the one radiator without one, is probably *too* close to the boiler).

-- JJ