Air source heat pump


Hi,
I'm looking to possibly get an air source heat pump to replace my very old and woefully inefficient boiler. Can anyone recommend any installers? I've had one round but the quote was ridiculous and they couldn't give a definitive answer on compatibility with my small bore pipe fed radiators.
I suspect the installers that are around are charging inflated prices to cash in one people wanting to go green, the actual wholesale prices I've seen for the pumps seem to be in the low thousands but the quotes run close to 5 figures :/
Thanks,
Peter.
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I have an air source heat pump, but it's separate from the heating system, and just heats my main room (which is also where I work when working at home). It enables me to work at home without having the central heating heat the whole house. (Also gets used as aircon on a few hot days in the summer.) It is a two-part self-install unit, which I bought from B&Q 3 or 4 years ago after fitting one for someone else and seeing how good it was. It was around 400 at the time, but that was on special offer. They still sell similar units, but technology has advanced a bit since I bought mine.
A comment I would make is that air source heating has a certain range of outdoor air temperatures over which it works, but also a range where it doesn't work. I tend to find the house doesn't need heating when the outside is above 15C (solar gain keeps the inside warmer). From 15C down to 5C, air source heat pump works fine. Below 5C, it rapidly gets less efficient as the outside evaporator ices up and has to run defrost cycles, which is great fun for sending large fog clouds across the garden, but is probably no more efficient (and maybe even less efficient) than simply using an electric fan heater. I haven't tried running it below 0C, but I suspect it wouldn't really work at all and if it's that cold, I would need the central heating to heat the house anyway.
--
Andrew Gabriel
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What kind or ASHP?
Air-to-Air - Individual units are 200+ on Ebay, DIY install - Multiple systems exist, one external, multiple internal
Air-to-Water - 8kW systems are 1000-1200 on Ebay, DIY install - You need oversize radiators or underfloor heating - Reason is the delivered temp-rise is limited
Low temperature performance - Current R410A refridgerant means poor performance <0oC - The metric is CoP, Coefficient Of Performance - 3.5 at 10oC means 3.5kW out for 1.0kW electricity - 1.0 at -5oC means 1.0kW out for 1.0kW electricity
- Future CO2 refridgerant means good performance at -10oC - They are rated to -25oC, but take UK as being -7oC re day - No idea of CoP but probably 2.0 at -7oC means "viable"
Generally you need a backup heat source. - For Air-to-Water perhaps E7 water storage or E7 storage heaters. - For Air-to-Air perhaps E7 storage heaters or gas wall heater(s).
ASHP are not within Permitted Development (unlike GSHP). They require PP, basically due to noise I believe. Just a note if you have cranky neighbours - although the noise is limited it comes down to reflections, superposition, rarefraction, reinforcement etc and so on depending on where you site the unit. Can't recall that area of physics right now :-)
CO2 refridgerant systems are here now - 4000 for 9kW as I recall from Sanyo (Daikin), probably Panasonic & Fujitsu etc very soon. Compettition & uptake will soon bring prices down - the cost is the two-stage high pressure compressor. That will really make even Air-to- Air work well in the UK and will finally spell the end of "1kW panel heaters", instead 2.5kW out for 1kW in which brings peak-rate down to E7 prices even during January in all but the most Northern parts of the UK.
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