How do Thermostatic Radiator Valves work?

17 January 2023
How do Thermostatic Radiator Valves work?

In this article, we’re going to look at thermostatic radiator valves, also known as TRVs. We’ll look at how they work and how best to use them.

So what does a thermostatic radiator valve actually do? It’s designed to automatically adjust the amount of hot water coming into a radiator according to the temperature in the room, NOT according to the temperature in the radiator, which is a common misconception we’ll come to shortly.

The operation of a TRV

How TRVs operate automatically is actually really simple. The heating flow comes up from the boiler in either a copper or plastic pipe (or whatever the plumber has installed). On the pipe, there is a nut, a valve seat and a pin. The pin can move up and down within the valve, which in turn allows water into your radiator. In addition, the pin will have a rubber or a copper taper on it. If the pin is pushed down, there will be no water going into the radiator, but if it’s lifted up slightly, water will be flowing into the rad.

The inner workings of a TRV

How does a thermostatic radiator valve automatically adjust where that pin is? On top of the pin is the thermostatic part of the radiator. This is the plastic bit that you twist with numbers on the side that correlate to how hot you want the room to be. Usually they have a responsive metal that will expand and contract as it gets hot or cold. The hotter something is the more it expands and the colder it is, the more it will contract.

Similarly, other thermostatic radiator valves will use a small wax canister and that gets warm, the wax will expand and push down. Other TRVs contain a metal coil. The metal coil sits inside the thermostatic part of the valve. According to the temperature you want in the room, you open and close the radiator valve.

The whole coil and plastic bit will move slightly up or slightly down. When the room is cold, the spring will contract allowing the pin to lift up and letting hot water into the radiator, warming the radiator up and therefore warming the room up. When the room is hot, the metal spring will expand and exert pressure on the radiator pin, shutting the valve and then stopping any flow going into the radiator.

In the video below, a professional plumber explains exactly how a thermostatic radiator valve works.

Don't make this classic TRV mistake

As you can see, it’s a very simple way of automating the amount of heat that goes in and out of a radiator, according to the temperature in the room. But this leads us onto the problem we’ve found of how people can use their thermostatic radiator valves incorrectly. Imagine you go into a room and it’s cold. You feel the radiator and it’s hot. That means that the TRV knows that the room is cold and it’s got the radiator on to try and heat it up.

What a lot of people will then do is look at the numbers on the side of the radiator valve, which will say for example, 3 out of 10. Because the room is cold, what people often do is turn the radiator valve up to 10 and that means it will never shut down, which defeats the purpose of having a TRV.

Energy efficiency and money saving

The biggest reason to install TRVs is to save money on heating bills. So if you go into a room that is cold, the radiator is hot and the TRV is working properly and you turn it up to 10, the radiator will never shut down and you’ll never save any money.

The best recommendation is that you turn all of your radiator valves to somewhere bewteen 2 - 3. This will enable you to have a comfortable temperature when needed, without wasting too much energy. TRVs are fantastic at managing heating on a room by room basis.

If there's a room that doesn't get used much (like a guest bedroom) simply turn your TRV a bit down a bit lower. The heating will come on if the temeprature gets really cold but you won't be blasting out heating in an empty room. That's the beauty of thermostatic radiator valves!


TRVs at Trade Radiators

Now you know how to get the most out of TRVs, you may be thinking of installing some or upgrading your existing ones. If so, make sure you check our fantastic range of thermostatic radiator valves where you'll find a huge variety to match your style of radiator! 

Keeping your home toasty and warm yet energy-efficient just got a whole lot easier thanks to the huge array of thermostatic radiator valves available from Trade Radiators.  

Many people are making the switch from traditional manual valves to something which can afford the user a bit more versatility and control when heating any space. 

A thermostatic valve means you can adjust the temperature of your radiator with just a simple turn of the dial. The easy to read numbers will accurately keep track of how much heat your radiator is putting out.

The valve works by setting a maximum temperature for your radiator. When this temperature is reached, the valve shuts. This stops the flow of hot water into the radiator, so the temperature remains constant, proving to be efficient for the user and help lower the need for your heating system to pump new hot water continually.

View all TRVs
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