The Pump is the Heart of the Central Heating System
Your central heating pump pumps water around your central heating in a similar way to your heart pumping blood around your body. So it stands to reason that if it isn’t working properly your hot water isn’t getting to the whole system. If it isn’t working at all you will find your boiler is working but the heating is not.
The pump only needs to work while the central heating is on, it does not need to work for hot water flow, so it usually stands idle over the summer months.
Heating Pump Seized
If you live in a hard-water area and you have not added a scale inhibitor to your system you may well find thatscale has built up on the diaphragm over the summer months while the heating has been off. See our project on Central Heating Problems for diagnosing more Central Heating Faults.
Replacing a Central Heating Pump
Replacement of a central heating pump can be awkward, because you are often working in the cramped confines of an airing cupboard. Don’t make the situation worse by trying to tackle it with the wrong tools make sure you have two fully-functioning and correctly sized spanners or better yet adjustable wrenches to prevent skinned knuckles and bad language! See our project on Spanners and Wrenches for more information.
DIY Guide – Install a Heat Pump
IMPORTANT: The pump is connected to the mains electricity supply. This must be turned off at the mains and disconnected from the pump before you change it.
1. Buy the right replacement pump.
To make sure you buy the right central heating pump replacement, check the instructions or manual for your old pump if you have it. You can also check the labels on the old pump to see if it lists the pump specifications (such as the speed ofpump, flow rate etc).
2. Turn off the central heating
3. Disconnect the power supply to the pump at the mains
4. Turn off the inlet and outlet valves. See photo below.
If the valve is stuck or jammed you can get help with that in our Projection Section.
5. Remove the electrical cover.
To help you rewire it correctly take a photograph or make a diagram of the connections.
6. Remove the electrical connection cover and release the wires from the earth, neutral and live, connections.
7. Unclamp the cable from the connection box and pull it away from the pump.
8. Undo the nuts connecting the pump to the pipe work using the adjustable spanners.
Do not undo the connection on the other side of the valves and pipe work.
9. Be prepared to mop up the water that will be in the pump.
Place a shallow tray and/or an old towel under the area you are working.
10. Put the new pump in position (don’t forget the washers) and tighten the connection nuts.
We recommend you don’t keep the old washers, replace them with new ones.
11. Dry everything off completely and then reconnect the cable wires as shown on your photo or diagram.
12 Replace the electrical connection box cover.
Again make sure there is no water present.
13. It is best to get the pump working as rapidly as possible so turn up your room thermostat for half an hour to an hour to really get the pump working.
14. Turn on the electricity and the central heating.
15 If there is air in the system use the bleed screw (example shown on the diagram). The process is exactly the same as bleeding a radiator, and if you are not sure how to do that go to our Project on bleeding radiators).
This is a moderately easy DIY job, but if you are nervous about working with plumbing, wiring or central heating then use our Find a Tradesman section to find a qualified and reliable heating engineer.
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