Radiator Valve Settings

[PrinceCharles]

Chaps,

What setting should the return valves on central heating radiators be set at, eg 1/4, 1/2, 3/4 or fully open? What effect would different settings have on heat output of the rad ( if any ) and would it affect the economy/efficiency of the boiler in any way?

Thanks

HRH

 

[dextrous]

They are opened according to the requirements for the system to be balanced - see the wiki for how to to this

 

[winty85]

Radiator valves do not effect the temp of the water inside the radiator. The valves with a spindle are used to balance the radiator system (ensure hot water reach each radiator in the house by restricting the flow to rads near to the boiler and forcing it to more troublesome radiators) Thermostatic valves can be fitted to save energy, they work by sensing the room temperature and switching the rad off when the desired room temp is achieved (again this does not effect the temp of the water inside the radiator.

 

[D_Hailsham]

Radiator valves do not effect the temp of the water inside the radiator.

Oh yes they do!

The more the lockshield valve is closed the slower will be the flow through the radiator and the lower will be the temperature of the water leaving the temperature. This means the average water temperature in the rad is lower. so the rad output will be reduced.

The valves with a spindle are used to balance the radiator system (ensure hot water reach each radiator in the house by restricting the flow to rads near to the boiler and forcing it to more troublesome radiators)

That's a very simplistic description. To use a very simple system as an example (see pic below). Let's say the main flow and return pipes are 22mm and the branches to and from each rad are 15mm. Because the branch pipes are smaller and the rad valves also create a restriction to the flow (have a look at the size of opening in a TRV4) the easiest route for the water is to bypass the first two rads and go though the last one. But this rad can only handle a certain flow, so the balance tries to go through the middle rad and then the first rad. When you are balancing radiators you are really trying to adjust the flow rates through them. It does not matter where the rad appears in the chain, a 2kW rad requires twice the flow rate of a 1kW rad. The total flow rate will be determined by the boiler and pump. It's a case of dividing this flow between all the rads in the correct proportion.

The LS valve will normally be somewhere between closed and one turn open in a correctly balanced system.

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• D_Hailsham
• 30 Oct 2008
• 1

Thermostatic valves can be fitted to save energy, they work by sensing the room temperature and switching the rad off when the desired room temp is achieved (again this does not effect the temp of the water inside the radiator.

Thermostatic valves do not act like an on/off switch. They are proportional controls, like a car accelerator, the open and close to adjust the flow rate through the radiator so the rad gives off the correct amount of heat to maintain the required room temperature. Of course the TRV affects the water temperature. If the TRV has closed down a bit (not shut off) the flow rate will be reduced so the average radiator temperature will be reduced and the rad output reduced.

How to Balance a CH System

 

[PrinceCharles]

Wow, I didn't realise just how intricate this balancing caper is. Thanks for all your advice, I'll have a proper read and attempt to set up as per instructed. Luckily I have an IR thermometer liberated from a job I was working on a couple of years ago.

I'll post how I get on.

Thanks again

HRH