Adding a radiator to your combi boiler heating system


Whether you are building an extension or wanting to combat a cold spot, there may be times when you want to add an additional radiator to your heating system.

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The first thing you need to know is whether your boiler has the capacity to support an additional radiator. Boilers come in different capacities, rated in Kilowatts. An average three or four bedroom house will have a boiler capacity of between 24 and 30 kW, which should be sufficient to run up to 10 radiators. A bigger property may need a higher capacity or even a different type of boiler altogether.

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Location and size

First of all, you need to decide where your radiator is going to go and consider how you are going to use the room, as putting a radiator in the wrong place can restrict your options. Also, think carefully about how the pipework is going to get to it and what disruption this might cause. Find the nearest pair of flow and return pipes – you can work out which is which when the heating first comes on as the flow pipe will heat up first.

You then need to work out how big a radiator you need for the space to be heated. You can use a British Thermal Unit (BTU) calculator to do this –

Fitting a radiator

Adding a radiator is a big job and you might want to get a Gloucester boiler repair specialist such as to do it. If you do decide to tackle it yourself then the first thing to do is to shut down the boiler and drain the system.

Fit the valves to your new radiator, using PTFE tape to get a good seal, then mark where the radiator is to go and fix the brackets to the wall. Make sure there’s around 125mm between the bottom of the radiator and the floor. You can now fabricate the pipework to connect the new radiator and this will usually be copper though some newer systems use plastic.

With everything connected you can refill the system – remember to add corrosion inhibitor. You will need to bleed your radiators to get rid of trapped air. You may find that adding an extra one has unbalanced the system so you’ll need to tweak the valves to get even heat.