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Air Source Heat Pump

We originally expected to replace the existing oil fired boiler with a ground source heat pump to provide the home heating. However there were many complications involved in doing this. There are two different types of system, either with or without a thermal store (a big water tank to store the heat collected). Of course, when you talk to different companies they say that their system is the best and I found it extremely difficult to decide which would suit our needs best. Most sources do suggest that it is normal to have a thermal store, but one big problem with a unit that has a thermal store is that it is big, very big! The only place we could locate one would be to either squeeze it into the utility room after removing the existing boiler or put it in the study. There was absolutely no way I would be able to prepare the underfloor heating in every room in time for a ground source unit to replace the oil boiler. Plumbing the low heat unit into the existing radiator system would leave us with a very cold house for few years until the house would be completely converted to UFH.

So removing the oil boiler immediately was not an option. The other option was to put the unit in the study but that also introduced problems. Firstly, with a thermal store the size of the study would be reduced considerably. However, the real problem would be how to run the pipes from the study out into the back garden. The corner of the house comes to within 2 feet of the boundary fence and that is also where the waste pipe runs from the house to the septic tank. Whether the system were in the utility room or the study we would still have to dig up the patio and go under the drains to put in the underground pipes, and the cost of a bore hole was simply too much. The study was the logical place for the new unit.

July 08

I took a few days off work to rip up the floor of Luke's bedroom and fit the underfloor heating pipes. I used Speedfit PEX pipe which was totally inflexible and a nightmare to work with. I fed the heating pipes under the floor and down into the study ready for connection to a new heating source when we get one.

September 2008
Not being able to see any real solution to this problem we decided to get in some professional help to see if they could resolve the issues. We called in a company called The Fuel Effect to quote on a ground source system but their sales rep agreed with the problems and immediately pushed towards installing an air source heat pump instead. They obviously install many units and are very confident in their service and the product they supply, the Altherma system by Daikin, and their quote came in at £7000 which was cheaper than the expected price of a ground source system. I then did some research into the air source heat pumps which is basically air conditioning technology but instead of heating air it heats water which is pumped around the UFH system. It is simple and proven technology, basically a fridge but in reverse, it needs no maintenance and is also very simple to install compared to ground source. The only downside of air source systems compared to ground source is that their COP rating is generally slightly lower and this reduces as the temperature gets colder outside, which is obviously when you need more heating. However, the simple installation really is a major benefit in our retro-fit situation so we decided that an airsource unit would be the way forward.

We therefore asked John (Sustainable Technology Ltd), who had fitted our solar panels, to also come in and provide a quote. He came in considerably cheaper than The Fuel Effect however he had never fitted such a big system before. We were however very confident that he would do a good job even if it took him twice as long. He did some investigation into the Altherma system and found that he would not be able to purchase and fit this without first attending a course with Daikin.

The outside unit was to be located next to the existing oil tank so our first urgent task was to clear the huge amount of brambles and weeds from the side of the house ready for the installation. The area was so overgrown it was difficult to open the gate to get in there. Over two weekends we got the area cleared and ready for the installation.

November 2008
With the help of Emma and Luke (always grateful to them for tolerating my demands) we prepared the study ready for the new air source heat pump which would eventually, hopefully, provide the heating for the whole house via the underfloor heating I am slowly installing. We had previously removed the corner cupboard where the unit was to be located so the main job was to run some hefty electric cables from the new consumer unit up through the loft and down through the eaves to the study. I also had to fit a water supply to allow the new heater unit to be filled.

The air source heat pump outdoors unit was installed in early November 2008 by John from Sustainable Technology and is basically an outdoors air conditioning unit. You can see the refrigerant pipes and airmoured electricity cables running along the wall. The indoor unit is about the size of a large conventional gas boiler but as well as providing heat it can be switched to provide cooling during the summer.

February 2009
We have found that the low temperature heating provided by the heat pump kept Luke's room at a very comfortable "room temperature" throughout the winter, but our bedroom was very cold, especially when there was a bit of a wind outside. We are now concerned about the setup of the UFH in our room installed by the plumber. I am concerned that he really hasn't done a particularly good job and now regret letting him do it at all. When he fitted the pipes he looped them out into the eaves rather than notching the rafters. I can understand his reasons for this but I honestly question his common sense when I had to explain that without any insulation on the pipes on the eaves we would simply be heating the outside world! Our other concern is that the particular underlay which was fitted (as suggested by the carpet shop) is not letting the heat through. I bought and fitted specific UFH underlay for Luke's room which seems to work perfectly well.

March 2009
In February I fitted the underfloor heating for the family bathroom and did a comparison between the grey polybutylene Polypipe I had used and the white Speedfit polyethylene pipe I had fitted in Luke's bedroom. I found that the PEX pipe releases the heat much better than the PB pipe which I believe is another reason why our bedroom remained cold while Luke's room warmed up. Unfortunately I think this means ripping up our bedroom floor and replacing all the pipework. What a nightmare, but at least I will be able to check on the plumber's workmanship. I only intend to use PEX pipe from now on even though it is very difficult to work with. This also means I have to replace the recently laid pipes in the bathroom.