Case Study: Installing an Air Sourced Heat Pump

Article, Energy & Housing

Ashp Video Martin Philips

by Martin Philips

Martin Philips lives in a house near Steyning, parts of which date back to 1480.  For some years he has been looking at ways to reduce his carbon footprint. After doing some research, in 2020 he installed an air sourced heat pump to replace an oil fired boiler.  He has been delighted with the results!

In this video case study Martin tells your all about his experience.

Some points to consider 

Here’s some advice from Martin on points to bear in mind if you’re looking at installing a heat pump yourself.

1) Obtain a heat loss survey for your house before you start, so you know what the heating demand for the property will be. It can be done by a heat pump installer or any good heating engineer. It must measure each habitable room, the insulation, window and door area and lost heat

2) They must also check each radiator size because ASHP run at 50C rather than the 60 to 65C of your boiler. If you do need any larger radiators, they normally occupy the same wall space as your current ones. They are just increased to a double or triple one.

3) The next bit is like choosing a car. First decide on which make. Grant, Mitsubishi (both made in UK), Daikin etc. But I suggest you select a manufacturer with Coefficient Of Performance (COP) above 4.0 to get the higher efficiency. Go onto their web site to find accredited installers and then ask one or two installers to quote you. Check the warranty from the manufacturer. Grant offer 7 years and I have found the product and the after sales support excellent.

4)  Your quote must include a new stainless steel hot water tank designed for heat pumps. It can simply replace your existing one. But if you have a combi boiler then the new tank could go in your roof space or in the corner of a room and be boxed in.

5)  Do ask for the next larger heat pump size than the one from the heat loss calculation. So if the heat loss for your house was say 7Kw then request the 10Kw pump (it’s a small price difference). This is to allow for the slight drop in COP at low temperatures and for the regular defrost cycles in cold weather. You can also go for a ‘hybrid’ system where your old boiler is retained and you can switch between them. But this may reduce your RHI money if the ASHP is not used sufficiently.

6)  If you want to use the RHI grant scheme you will first need to have cavity wall ( if you have cavity walls) and roof insulation in place. Also an EPC (Energy Performance Certificate) done in the last 2 years, as you would if you were selling your house. I don’t think the actual EPC rating matters. You then receive 60 to 70% of the initial cost paid back over 7 years from OFGEM. There are other grants such as the Green Homes Grant to assist with the upfront cost.

7) If you are happy to proceed the work should be complete in 2 to 3 days. ASHP are basically very simple devices and only produce cold air and a trickle of clean water. They are mounted next to an outside wall where 2 pipes and a cable are brought into the house to connect to your existing hot water system.

8) You must get the MCS installation certificate when the work is finished if you are claiming the RHI grant. This should contain include some insurance backed warranties.

9) The house may ‘feel ‘ different in winter to the boiler heating you are used to. This is because your boiler is cycling on and off with radiator temperatures going up and down. ASHP tend to keep radiators at the same temperature throughout the day. This is automatically adjusted to match the needs of the house with outdoor temperatures. It is called automatic weather compensation which set up during commissioning. We find our house now feels warmer even though the wall thermostat is set at the same temperature as with our boiler.

10) Costs and savings . This will vary considerably depending on the ASHP size and any radiator changes required. There is no short cut to getting one or two quotes in and then making your decision. Savings will be somewhat higher for replacing oil than gas boilers.

11) These notes are for guidance only and I take no responsibility for accuracy or the advice!