fisher wrote:Gan020 wrote:I've had an ASHP for 8 years along with solar PV and solar thermal panels. The solar PV and solar thermal panels have been fantastic. The ASHP whilst financially well worthwhile has been a little disappointing in terms of the drawbacks.
Out of interest, what do you see as the drawbacks?
The major drawback is the time the system takes to heat up in combination with the noise of the unit.
I have a Mitsubishi 3 phase unit which apparently is the maximum size you can put on a domestic supply. It is sited on an outside wall of the house. In the depths of winter when the temperature drops below zero, the noise it makes on the defrosting phase is in my opinion unacceptably loud. (when it's cold the back of the heat exchanger gets covered in ice so this has to be removed by heating it up else there is no air flow for the ASHP). The noise volume is probably less loud at this point when the ASHP is running continuously but after a while you don't listen or hear the fan noise in continuous operation as it's a constant drone in the background. The noise of the defrost cycle is more noisy because of the way the noise kicks in and out. It doesn't seem to bother my sleep when the temperature is above about -3 but anything below that and it disturbs me. It doesn't bother my wife at all.
Because of this I do not run the unit 24 hours a day and avoid running it overnight. I do use it from 3-4am to heat the hot water on overnight tariff, but somehow the defrost cycle doesn't bother me then presumably as I'm in deep sleep. I then start it up at 6am in Nov through Mar but of course it can't raise the temperature in the house as quickly as I would like. I do route the water through my rads to the rooms I want heated first which helps but it's not as warm as I'd like it first thing.
What you need with an ASHP is a modern well insulated house. Mine was built in the 60's with later extensions and whilst the heat losses from the house are such that the ASHP can keep it warm with ease in everything but the Beast from the East (when I suspect it wouldn't matter what you have for heating), getting it raised to tickover temperature can take 2-3 hours in Oct/Nov/Mar/Apr. For the coldest 20 days or so of the year when I heat all the rooms when the kids are home from University and we have visitors staying it really struggles and takes 4+hours. If a couple of rooms aren't being used and I turn the radiators off in those rooms the temperature in the rest of the house picks up much more quickly which is telling me my house it getting close to the point if I put some more insulation in, change some windows or curtains or floor underlay or whatever the ASHP would be alot better to live with.
For the past 8 years I've been slowly improving the heat losses from the house. What I can tell you here is that every time you sort the heat losses in one place they move elsewhere (or you become more aware of them). I've now got 3 rooms which heat up reasonably quickly and once that's done the TRV's on the radiators in those rooms turn off and there's more heat to spread around the remaining ones and the overall temperature in the house accelerates. If you are using radiators rather than underfloor coils you will need to make sure your rads are large enough and regrettably I've a couple that aren't even though they were sized by a professional. Finally my wife likes radiators that aren't the standard oblong ones. This isn't possible though as they don't have the heat output in relation to surface area.
I am thinking of getting some electronic TRV's so I can better control the on and off times by zone in each room. This would definitely help push the heat where I want it better. Regrettably they are still quite expensive when you compare with simply turning up the heating an extra 10% or spending the same amount on insulation. Nevertheless I shall probably try this out at some point.
It is cheap to run. My total electricity bill for everything this year is around £1400 although it has been mild and we went away for 10 days in Feb. Usually it would be £200 more. I have no gas but do have solar panels for both electricity and hot water. My house is a large 4 bed house. I'm not sure what large means but I have two rooms in which I can fit a snooker table in if that helps and a kitchen large enough to fit another although that of course would be a very strange thing to do indeed.