Heat Pump in Highfield

Experience of installing a heat pump

Section 1 – how our journey started

Over the last few years, we have been thinking about reducing our carbon footprint as have a lot of other people. The key changes that would have the most impact are moving to a more plant based diet, reducing the amount of travel fuelled by fossil fuels and replace our gas central heating system with an electric system.

Being members of Highbridge Community Farm and choosing local food wherever possible helps with the first one. The second one is more difficult – we cycle as much as possible and I suppose at some point we will buy an electric car. But it is the third one that we have decided to tackle head on. We already buy our gas and electricity from Good Energy – they generate their electricity from their own wind farms and solar arrays. Our carbon footprint would reduce by about 60% if we move away from burning gas.

As I write this, we have heating engineers in the house taking out our gas boiler and replacing it with an air source heat pump. It is probably the wrong time of year to do it as we will be without heating for a few days this week!

The purpose of this piece is to share how we have got to this point and to let you know how the system operates. There has been a lot of negative press about heat pumps – they are said to be noisy and do not generate sufficient heat. We will soon find out if these claims are true or not.

Section 2 – planning the heat pump

We are a week into the installation process and today the pump should be switched on. More on that later.
Getting to this point has taken about a year. Our house is detached and has 4/5 bedrooms. The main part of the house was built in 1954 and had various extensions in the 1970s, 1990s, early 2000s and 2020. It had double glazed windows and cavity wall insulation. We knew that we had to increase the insulation in our house in order to be eligible for an air source heat pump. We had previously emptied our loft so it was straightforward and relatively cheap to to double the depth of insulation. The house has a large integral garage with a bedroom above which was always difficult to heat so we got a local builder to add insulation into the roof of the garage.

Once we had done this, we decided to to have an energy performance survey carried out hoping that the house would fall into the C category. Luckily it did which indicated to us that we could realistically have a heat pump.

About 8 months ago, we received an email from Good Energy, our energy supplier, saying that the company had just bought Igloo Works, the heat pump provider attached to Igloo, one of the failed energy providers. We filled in a simple questionnaire on line and it was followed up by a visit from an Igloo (now Good Energy) surveyor. He spent a couple of hours measuring each room and calculating heat loss – from the data collected he produced a report that confirmed that our house would be suitable for a heat pump. The report stated that some of our radiators would have to be changed for larger ones – the heat pump produces cooler radiators compared to a gas boiler so they have to have larger surface areas.

Over the next few months, we had a lot of discussion about the location of the heat pump. We had wanted it at the side of the house but unfortunately the distance between our wall and our neighbours’ was 20cm too short to allow for maximum efficiency of the pump. We found a position at the front of the house which meant obtaining planning permission which we eventually got. So by October this year, we were ready to go. In the meantime, the Government had increased the grant for a heat pump from £5000 to £7500. This meant that it would be costing us about £11,000 as opposed to £18,500. But still a lot of money!

Section 3 – does it work?

It has been about four weeks since we had our heat pump switched on and since then we have had a houseful of people in the house over Christmas and we have experienced some cold weather. So I think it a good time to let you know how it has performed.
The heat pump is designed to provide all our hot water needs as well as run the central heating. The management of the system is very different from our previous gas system in that it is switched on at all times. With the old system in the winter we would generally put the water and central heating on twice a day and top it up when necessary. Now we have continuous hot water and we can control the house temperature using an app on our phones. This means we can control the house temperature in blocks of time of our design.
The system is much less responsive compared to a gas system. This is because the temperature of the radiators is about 50 degrees compared to about 70 degrees in our old gas system. With cooler radiators the rate at which the house changes temperature is quite a lot slower and so we tend to keep the house at between 15 (at night) and 17.5 degrees. We have noticed that we are getting a more even temperature in the house. We have also noticed that with the cold weather the heat pump is working much harder and increasing the temperature of the radiators slightly allowing the house to reach the set temperature.

During cold weather the heat pump becomes less efficient as it takes heat from cold air. However, we have been told that averaged over the year the pump should have a seasonal coefficient of performance (SCOP) of 3.59 – that means for every 1kWh of electricity used to power the pump 3.59kWh of heat will be produced.
The sound level of the pump varies according to how hard it is working. When working at its maximum, we can hear the pump – it is outside our kitchen window. The noise is well within tolerable limits and not much louder compared to a gas boiler. It is worth noting that from Spring to Autumn the pump will be operating for short periods of time and at well below maximum effort.

Any snags? The hot water system is now pressurised and as the system was switched on a hot water pipe to a basin sprung a leak. This was easily fixed but it is worth noting that old pipework could be susceptible to leaks if it is pressurised. We have also found that we will need to replace a couple more radiators for larger ones in rooms where we feel that a higher temperature is needed. The cost of running the system is a bit more expensive (about 10%) compared to our old gas boiler but the advantage is having the house continually at a comfortable temperature.

Are we pleased with the heat pump? Yes, we are. Just looking at the machine as it takes heat from the air and pumps it into our house is awesome! We are also confident that if we have problems, the company that fitted it will deal with it.

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