How to Replace a Central Heating Pump - A DIY Guide to Replacing a Central Heating Pump

Summary: Step by step guide on how to replace a Central Heating pump, and how to make sure it is working effectively. A faulty central heating pump can cause Central Heating faults. We give you advice on diagnosing heating pump problems and fitting a new pump.

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Replacing a central heating pump can sometimes be a little awkward because of its position in the airing cupboard or similar. The basic rules however remain the same and if you are struggling with an old spanner which does not fit properly, please use the correct tools for the job. It really does make life so much easier.

Adjustable spanner

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To change a central heating pump you will need a couple of large adjustable spanners (Stilsons are probably the best type of wrench to use here, but if you can't get the stilsons in, see our project on spanners and wrenches)

Click on the images of the tools to buy or go to the tool store to the right of the page.

The heating pump pumps water around your radiators, from the boiler, keeping them supplied with hot water . A good indication that the central heating Stilsons are easiest to use for replacing central heating pumpspump is playing up is if your radiators are hot at the top of the house, but cold downstairs. See our project on Central Heating Problems for more on faults within the Central Heating System. If this is the case it can sometimes be overcome by turning the pressure up on the pump.

The heating pump is powered by electricity. This must be turned off and disconnected from the pump before you can change it. You must also turn off the central heating.

Before you buy a new pump, look at all of the labels and writing on the old pump. Many of these will contain pump specifications (speed of pump, flow rate etc) and will make it much easier for you to buy the correct replacement.

Also (having made sure the electricity is off) take off the electrical cover and take a digital photograph (you can even use your phone) of the connections inside. If you cannot take a photo, make a diagram of the connections. This will help you put it all back together properly. It is much easier to have all of this information now that to struggle later.

Central heating pump in position Fully explained central heating pump

The image on the left shows a pump in position near the floor of the airing cupboard.

Remove the electrical connection cover and release the wires from the live, neutral and earth positions. Unclamp the cable from the connection box and pull it clear of the pump.

The inlet and outlet valves need to be turned off using an adjustable spanner. These valves will turn off by turning them clockwise. If you have trouble with a valve that is stuck or jammed, click on the link to our project on this.

Undo the nuts connecting the pump to the pipework using the Stilsons. Do not disturb the connection between the other side of the valves and the pipework.

There will be some water in the pump. You can either place some rags under the pump or a shallow paint roller tray to catch the drips. Keep the washers if you have to but it is best to replace these too.

Place the new pump in position (don't forget the washers) and tighten the connection nuts.

Remove the electrical connection box cover and use a light cloth to make sure no water is present. Reconnect the cable wires as shown on your photo or diagram.

Turn up the room thermostat (to get the pump working as quickly as possible) and reinstate the electrical power to the pump.

Turn on the central heating.

There may be air in the system after changing the pump. This can be bled out by using the bleed screw shown on the right hand diagram. Open it gently until you hear a hissing (Just like bleeding radiators). It may also be necessary to bleed the radiators.


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