DIY Doctor UK DIY Forums

Has anybody got an Air Source Heat Pump installed in their home to provide central heating, and DHW?

If so, does it work? do you get on with it? and would you recommend one to anybody else.... like me?

One other question, are they expensesive to run? I understand that it's all down to how much hot water you use and how well the house is insulated etc? but compared to heating the house with oil is it cheaper?

I'm very interseted in having one to replace an oil fired boiler, but as i have no experience of them i'm not sure if its the right thing to do.

Thanks, Robert and Susy

Hi don't have ASHP at home (use solar panels) but have installed them to heat swimming pools and commercial buildings.
Rule of thumb for running costs is for every kW of electrical energy used to run unit you get around 3 kW of heat output from HP unit.
So depending on cost /kWH (UNITS) you pay for leckie against cost of oil you must judge.
Problem is not having conversion tables from one to the other readily available, theoretically a 30kW boiler should equate to 10kW electrical input to ASHP. However whilst you can measure electrical energy easily you don't know how much oil you use to produce 30kW from boiler.
BTW ground source type give 4kW out for each 1kW input.
Try one of the web sites devoted to alternative energy, most are quite helpful, eg Energy saving trust,
regards Sparx

Hi

I installed a Mitsibushi Ecodan air source heat pump system last August. I have had a miserable winter.

First the system does work, heat is collected from the outside, even at sub-zero. However, the good news ends there. It is a new technology and a chose a local installer from those approved by Mitsibushi on a list they supplied. The dealer also featured in their publicity brochure and video. I am a pensioner and have no heating knowledge and had to rely on the installer, particularly with the Mitsibushi recommendation behind him.

I now appreciate how important it is that heat loss calculations are carried out on the property for a retro fit. It has become very clear in hindsight, that this was not done and that the heat pump is under size. My house is well protected with cavity wall, double glazing and well insulated loft, but the installer failed to do the basics, although I gave him all the room sizes when he surveyed the property. The heat runs through the system (assuming a correct size Ecodan) at 55 degrees, instead of around 70 for a oil/gas installation. Therefore, all radiators have to be changed to increase the surface area by about a third.

In addition to an undersized system - the warmest the lounge has got through the winter is 17, on coldest days 15 - the Ecodan comes packaged with a Gledhill tank. This has been nothing but a problem. It is difficult to program times, but more importantly we have had trouble with elements of it, including needing new printed circuit boards and being without any heating or hot water for a week while they were replaced.

My advice, is look very carefully, if it is a retro fit. Check out the installer (I thought I had since Mitsibushi featured them so strongly) and be very careful to look close at the unit which comes with the air pump. This unit drives the whole process and is the 'brains' of the system. Additionally, since it will become a sealed system under mains pressure, you have to be very sure of all joints etc in the existing system – we found this out the hard way!