Question about radiator valves

  al's left peg 16:14 19 Oct 2010

Hi guys,

I am looking for a bit of advice regarding thermostatic radiator valves. I am thinking of installing them in my house and need to know do I have to install a new lockshield valve on the other side of the radiator or will the existing one suffice?

Any advice greatly appreciated, cheers Al.

  Forum Editor 16:46 19 Oct 2010

Just make sure that it's fully open, and that it stays that way.

  al's left peg 16:57 19 Oct 2010

Thanks FE,

I have noticed that I can buy reversible flow valves so I don't have to find the flow or return pipe and just fit it to the side I choose.
Will tick as resolved thanks for your advice

  [email protected] 17:00 19 Oct 2010

There is no point in changing the lockshield valves unless they are leaking or "Senior Management" dislikes the appearance of them.

They are used to balance the system and once adjusted need no further attention. ( You should aim for a 20 degree drop across each rad. )

I have just installed TRVs on our radiators and left the original lockshield valves in place , the system didn't need balancing ! They are working well and hopefully will save on fuel this winter !

  Pineman100 17:01 19 Oct 2010

I agree that the lockshield valves should be left in place, but I'm afraid I disagree about leaving them fully open.

A central heating system with TRVs still needs to be balanced, using the lockshield valves. If this is not done, you can greatly extend the amount of time that it takes for the last few rooms on the circuit to heat up, when the system starts up.

You should not install a TRV on the rad in the room where your roomstat is located, and you should incorporate an automatic bypass pressure balancing valve in the system.

This may help: click here

  namtas 17:06 19 Oct 2010

Each lockshield valves on your system must be set up to balance the system. You will have a totally unbalanced system if you leave them open.

  [email protected] 17:10 19 Oct 2010

I totally agree , the sytem must be balanced as namtas and pineman100 state . I was lucky in that my system stayed "in balance" with the original lockshield settings.

  [email protected] 17:16 19 Oct 2010

How to go about it :-

click here

  Graham. 00:01 20 Oct 2010

Balancing is no longer relevant with thermostatic valves, they take over that function.

  Forum Editor 00:36 20 Oct 2010

and the system is fully flushed and has corrosion inhibitor added there will almost certainly be no need to fiddle around balancing the system when you install Thermostatic valves.

You will certainly not need to replace the lockshield valves.

All that's necessary is to fit the new valves, fill the system (adding corrosion inhibitor as you do so), and fire the boiler. Fully open all the TRVs and all the lockshield valves. Leave the lockshields alone, and regulate the temperature in each room using the TRV. It will take a little while to get right, but it's easy to do, and there's absolutely no need to play with the lockshield valves - leave them open, as I said earlier.

If your boiler is a modern Combi type it will almost certainly have an automatic bypass valve built in, or on an earlier system you may have one fitted at some point in the system. Many heating installations have a small radiator - often in an airing cupboard - that has fully open lockshield valves at each end, and acts as a bypass.

With TRVs you don't have to worry about finding which is the flow pipe by the way - these valves will function just as well on the return pipe.

  namtas 11:04 20 Oct 2010

I am sorry but I cannot agree that locksheilds (or balancing valves as they were called) should be set wide open on a normal domestic CH system.
However I accept that perhaps a new valve has been developed which I am not aware off, in which case I would welcome information.
A domestic CH radiator has a design output rating which it will only provide its rating at a specific flow and temperature. By running a system with all the lockshield valves fully open, then a cold room will call for the thermostatic valve to be wide open to meet demand, and obviously will only close down on temperature satisfaction. Now if that associated radiator happens to be one nearest to the system circulating pump then with the lockshield wide open and no restriction the radiator will receive full flow. As a result it will provide excess heat output but in so doing reduce the available flow (and consequent efficiency) of every other radiator in the system. As a consequence the boiler, sensing a return of water at or near its expected return temperature will short cycle off and on as it tries to meet the short circuit flow, the result is a loss of efficiency from the boiler. Long term this will have an effect on the boiler and could possibly cause problems. A note should be made that a permanent bypass must be provided on the system at some point if fitting temp variant valves.

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