thermostatic radiator valves

[Geoff Norfolk]

Hi I just fitted 5 TRV's to the radiators in my bungalow, leaving the one in the bathroom as it was. One radiator, a double panel one in the living room is causing problems. When the valve is just on the point of completely shutting off, it starts vibrating really noisily........... if I press on the top, it stops. If I turn it a fraction either way, it stops until it reaches the exact point where it's about to shut completely. These were very cheap valves..... about £5 each from Screwfix.......... however none of the other radiators do this. I've swapped the tops over from another radiator but that made no difference. There's no air in the rads. The valve is on the in feed to the radiator however the valves can be at either end of the rad according to the instructions. I had a look at the pump and it was set at maximum speed and I've found that by turning the pump down to the slowest setting, the valve stops vibrating and just makes a slight "clonk" when shutting off. Is ok to run off lowest pump speed or will this cause problems in very cold weather with the radiators not heating up enough. I would have thought a bungalow wouldn't really need the pump set to high as the rads are all on the same level.

Geoff

[Bob Minchin]

I've just fitted a TRV yesterday. It looks like the screwfix ones but came from Toolstation and are branded OPTIMA. The instructions say that pump pressure should not exceed 0.2bar under all conditions to prevent noise. A quick fix would be to drop the pump speed but ideally fit a bypass valve set below 0.2 bar and turn the pump up to a suitable speed to distribute the heating at max demand.

HTH

Bob

[Set Square]

The only relevant question is whether the pump can circulate sufficient water at the low setting to maintain a temperature drop of not significantly more than 11 degC across the radiators in cold weather with the LSVs fully open and the lockshields adjusted to provide a proper rad to rad balance. This depends on the power of the pump and the length of size of pipework. Whether or not the rads are on the same level is completely irrelevant - the 'up' and 'down' legs cancelling each other. The pump simply has to provide

*circulation* - and doesn't have to push anything up hill.

[Dave Plowman (News)]

In most all circumstances, all the pump needs to do is overcome the friction or 'head' in the system. If all the rads are getting hot then it is doing just this. Running it faster than needed therefore only makes more noise - and could cause other problems, like pumping over in a non sealed system.

[graham]

Whilst we are on the subject, I was thinking of fitting thermostatic valves.

Is it possible to get an adator kit to make some valvesthermostatic, rather than having to remove the existing valve and install a new one?

Graham

[Dave Plowman (News)]

Don't think it would be possible. Lockshield valves screw to adjust - TRVs use a needle in a seat to regulate flow. To use the lockshield principle you'd need some form of stepping motor - and an electrical supply.

FWIW, unless you're sure of the condition of your system, draining down the system to fit TRVs, and re-filling with fresh inhibitor is no bad thing anyway.

[Phil Addison]

Some possibilities are

1 The TRV is fitted in the wrong flow direction; some do have an arrow on them indicating required flow. Chattering and knocking is often a result.

2 The rads are not balanced so that this rad is receiving more than its fair share of pump pressure.

3 Both of the above

See the FAQ for balancing instructions.

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

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