Thermostatic Radiator Valves – Plumbing Tips

Posted by in Plumber Talk, on March 7, 2017


This video covers thermostatic radiator valves. How they work and how you can install them. We also cover which room to install them and why. For more information visit:

Welcome to today’s video. Today we’re gonna look at thermostatic radiator valves otherwise known as TRVs. They individually control the temperature in the room to an individual radiator. Firstly, we’re gonna have a look at how to change them. And then we’re gonna have a look at how they work. I hope it’s very informative. Hold tight.
So how does a thermostatic radiator valve work and what’s the difference between that and a normal radiator valve? Well firstly, a normal radiator valve is just valve that moves up and down and shuts off the flow of hot water from the boiler into the radiator. Just like the tap on a bath tap. The main difference with a thermostatic radiator valve is that it automatically controls the amount of hot water going into a radiator according to the current heat of the room that it’s situated in. There are two types of thermostatic radiator valve. One uses a spring that expands and contracts. And the other uses a wax jacket that does exactly the same. For this video, we’re going to look at the spring type because they both work in a very similar way. So we have a spring that is made of metal, that is very susceptible to the temperature around it. If the room is cold, the metal will be contracted because when metal is cold, it is contracted. Therefore the valve jumper will be open and hot water will be allowed to flow into the radiator. If the room is warm, the spring will expand and that valve will be pushed down and the flow to the radiator will stop. And that’s how they work. A very common problem I have with customers is, sometimes they’ll come in, the room is cold, the radiator, when they feel it, blazing hot, and they still go to the thermostatic radiator valve and open it up more. That’s completely pointless. The room is cold, the radiator is hot, therefore the thermostatic radiator valve knows that the room is cold and is trying to heat it up. If you go into a cold room and feel the radiator and it’s hot, do not tough the thermostatic radiator valve. Only touch it when you go into the room and it’s cold and you find that the radiator is cold. Also another thing you need to consider is where you can actually instal thermostatic radiator valves. If you have a house with two rooms. In one room, you have room thermostat which controls the whole heating system and one radiator. In the other room, you have another radiator and that has a TRV on it. Don’t put a TRV in the room that has the room thermostat in it. The reason for that is if the TRV closes down and the room thermostat is not satisfied it will never knock the heating system off to the whole house and you won’t get any saving. That room thermostat there needs to have an exactly true reading of the maximum capacity that the heating system can give out. Therefore, the radiator in the room with the room thermostat should have a lockshield on it that is fully open. So let’s go back to the house and find out how you actually change a lockshield over for a TRV and really how easy they are to instal. I’m assuming you all know how to drain down heating system already. Finding the lowest point in the heating system and drain off, taking a hose outside and opening that up and making sure the water supply has turned off to the heating system. Next you allow air into all the radiators you want to change in the TRVs. Generally if you’re a bit worried about this then air into every radiator in the house. (hissing) You should hear the air sucking. As soon as you see your hose outside stop running, that should indicate that the heating system is drained down and you’re ready to change the valve. Let’s have a look here. As you can see, we’re removing this old lockshield here which is just an on and off valve. So now we know that the system is all drained down. We can loosen that off. Now’s the time just to make sure that the water has drained out of the system. As you can see it has. And then we can loosen off the mil compression fitting on the bottom. As you can see, our new TRV isn’t going to fit on this current radiator insert. All new TRVs are supplied with a new insert. So this one here will need removing. There are special tools to do this. You can have a hexagonal tool that goes in like that. A square tool, a lug tool cut in here. This is quite an old one as you can see. Today I’m going to use this here cuz we’ve got a hexagonal fitting on there. Now often you can just lift up and make it round. But generally you’ll have to adjustable spanner on like this and then wind it out like that.

Leave a Reply

Your email address will not be published. Required fields are marked *