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How To Replace A Small Radiator With A Large One

Today we’re going to run through how to replace a small radiator and put a longer radiator in it’s place. This is a particularly common scenario when you have a large room. The problem with a small radiator in a large room is it has too little British Thermal Units (BTUs) going into the room and heating it up.

Where possible, it’s always a good idea to put radiators under windows. The reason for this is because they don’t have a great thermal efficiency and therefore, as the cold air comes in, the radiator under the window will warm that air as it comes into the room.

Before we begin, we make sure that we’ve turned off the heating system and it’s all drained down and that all the radiator valves are open. Then the old radiator is ready to be removed.

So we’ve removed the old radiator and capped off one of the pipes going to the return of that radiator. The flow pipe can be used again for the new radiator when we hang it up under the window. We’ve also got our floorboards up and exposed all the pipes that we need to work on. The next thing we need to do is actually hang the radiator on the wall, so we’ll go in the other room, unpack the radiator and start getting our measurements.

Before you unpack the radiator, make sure that you check for damage. Also make sure that you find the two brackets (or three brackets if it’s a big radiator) and pop them to one side. Also look for the small box that contains the grommets and inserts for the radiator. Undo this box at the end – you’ll have instructions, air bleed insert, blanking plug insert and also the grommets that go onto the radiator bracket. We going to have our radiator standing off the wall by the smallest distance so we’ll pop our grommets onto the brackets. What they do is prevent the radiator from clicking when it heats up and from making noises when it rubs against the metal brackets.

Remove the travel plug and pop in your insert. You’ll notice there’s a rubber washer around it so it shouldn’t require any sealant. Then tighten it with your grips. Do the same at the other end and pop your air bleed in. It’s worth remembering that you should always pop your airbleed at the end of the radiator that you know you’ll be able to get at once it’s installed on the wall. You don’t want to install it really tight against another wall, otherwise you’ll never be able to get to the bleed to actually bleed the radiator down, or it will at least be very difficult.

Another thing worth noting is that you can take the top and side grills off and actually turn the radiator the other way up to make it a round top radiator, so it can be converted to two different types of radiator.

Now we’ve prepared the radiator for going in, all we need to do is think about where our brackets are going to be. The first thing to do is to measure the distance between the centre of each of the brackets. (In our example radiator, it’s 108cm).

Now the next thing to do is to mock up the bracket actually hanging on the radiator and measure the bottom of the bracket to the bottom of the radiator itself. (On our example radiator, that is 11cm)

The next thing to do is to measure the width of the window itself, divide that by two and that will give us the centre. Make a tiny mark in pencil and make a straight line using the spirit level down the wall. Now we want to determine what height we want the radiator at. Our example radiator is 400mm high and we want the top of the rad to be just below the window sill. So we also mark the bottom of the radiator with a pencil mark. All we then do is measure up 11cm (the distance between the bottom of our radiator and the bottom of the bracket) and make a small mark on the wall.

We know the width between our brackets is 108cm, so 108/2 = 54cm and we’ll mark that accordingly. We’ll use our spirit level to draw a straight line between both of our marks. So we have a spirit level horizontal line and we’ll then use a small spirit level at each point where we’ve marked the brackets to make a line to make sure the vertical point is truly vertical.

The next thing to do is with each mark, we put our bracket on the bottom of the line and the side of the bracket against the vertical line. Mark all the holes on each bracket and do it at each end. Get yourself the right size drill bit and firstly drill your slotted hole. Do that at both ends as you add both brackets, then place the spirit level horizontally across both brackets to check they’re level. Then put on the remaining screws and plugs.

Grab your radiator and pop it on, bottom first, and push it up onto the brackets. You’ll notice once this is done that your radiator can slide from side to side on the brackets. Now is a good time to measure it out to make sure the radiator is central. The radiator is now in position and we’ll now know exactly where our pipes need to come up through the floor. We’ll know where to put our thermostatic radiator valves (TRV) and lockshield on to our pipework.

Remove your TRV from the box and put PTFE on the valve thread. (The more the merrier, as PTFE is cheap but leaks are expensive.) Wind the screw into the side of the radiator. Make sure that the TRV you get has the Two Arrow sign on it, that means it’s universal and can go on either end of the radiator regardless of the flow or return. Follow the same process with the lockshield at the other end.

We’ve now got the radiator hung on the wall and we’ve got our valves in so we know exactly where we can bring our pipes up. If doing the pipework yourself, make sure you’ve tightened all the nuts up and all your solder fittings have been done, but before you put the floorboards down, make sure that you’ve got no leaks by filling up the system, pressure testing and making sure that everything is fine there. After you’ve done that, you can pop your floorboards down, your underlay and your carpet, or whatever you had on the floor beforehand.

You can view a video of this entire process on the Trade Radiators YouTube Channel here

The radiator featured in the main image is the 1400x400mm 4 Column Radiator

Article by Benjamin Clarke