Air Source Heat Pump
Discussion
Jambo85 drop me a PM please?
I would agree with the comments on the performance of system at low temps too as we found especially when it was cold for several days running the daikin would struggle a bit. In regards to the defrost cycle if I am correct it also needs sufficient volume to ensure it can do this for the rad it it linked to. I was more curious about manufactures than anything as only had experience with Daikin.
I would agree with the comments on the performance of system at low temps too as we found especially when it was cold for several days running the daikin would struggle a bit. In regards to the defrost cycle if I am correct it also needs sufficient volume to ensure it can do this for the rad it it linked to. I was more curious about manufactures than anything as only had experience with Daikin.
I spent 2 weeks in Sweden with an A2A HP keeping me quite toasty in a holiday chalet. It was -27C outside. I can't say I know what the bill was, but it was more than capable of doing its job.
Fan assisted radiators are also a useful touch to a A2W system, but it does further add to the complexity. It's probably the path I will have to take, short of digging out my ground floor.
Fan assisted radiators are also a useful touch to a A2W system, but it does further add to the complexity. It's probably the path I will have to take, short of digging out my ground floor.
Silent1 said:
surely a ground source heat pump is a better idea in this country, presumably they can be plumbed in borehole style to take advantage of stable-ish ground temps
Higher initial costs, lots of small gardens in newer homes.Personally, I'd love to see more district systems using water source. Caerau Mines is an example that's being explored (mine water stays at a consistent 20C).
Evanivitch said:
I spent 2 weeks in Sweden with an A2A HP keeping me quite toasty in a holiday chalet. It was -27C outside.
With modern levels of insulation and airtightness, and MVHR, we can design dwellings that don't really need a heating system at all - they can retain sufficient heat from incidental sources like cooking, solar gain and bodyheat.I wouldn't suggest that the OP just rips out the heating system altogether on his 1993 brick-built house either, though.
At that sort of temperature, incidentally, any mainstream ASHP will be operating at a COP of 1.0, near enough (possibly less, with frost cycling). So whilst it will still work, if the unit is sized correctly, it will be no more efficient than direct electric heating.
Evanivitch said:
Caerau Mines is an example that's being explored (mine water stays at a consistent 20C).
Strictly speaking, that's geothermal.Evanivitch said:
Nope, that would be like saying GSHP is geothermal.
GSHP uses ground at 'normal' ground temperature, within a few feet of the surface. The ground temperature at that level is linked to the climactic temperature, moderated by the thermal mass of the ground itself.Caerau Mines, as you pointed out, uses the great depth of the mine to access geothermal. temperatures. It is constant, as near as makes no difference - and much higher than surface ground temperature.
Edited by Equus on Monday 20th January 09:55
Equus said:
GSHP uses ground at 'normal' ground temperature, within a few feet of the surface. The ground temperature at that level is linked to the climactic temperature, moderated by the thermal mass of the ground itself.
Caerau Mines, as you pointed out, uses the great depth of the mine to access geothermal. temperatures. It is constant, as near as makes no difference - and much higher than surface ground temperature.
A GSHP bore hole will be 20-120m deep.Caerau Mines, as you pointed out, uses the great depth of the mine to access geothermal. temperatures. It is constant, as near as makes no difference - and much higher than surface ground temperature.
Edited by Equus on Monday 20th January 09:55
Caerau Mines are 230m below.
A geothermal Powerstation goes to 1km to 10km.
So yes, the mine is heated by geothermal activity, just like a deep GSHP borehole is, but it still uses a heatsink method to draw relatively cool water (20C is cool in geothermal terms) to the surface to an exchanger that subsequently feeds a heat pump at the property.
Equus said:
Evanivitch said:
So yes, the mine is heated by geothermal activity
Glad you agree with me.Most GSHP installations are not deep boreholes, of course: they're either a horizontal loop, close to ground level, or a vertical array of shallow boreholes.
Evanivitch said:
A GSHP bore hole will be 20-120m deep.
Caerau Mines are 230m below.
A geothermal Powerstation goes to 1km to 10km.
So yes, the mine is heated by geothermal activity, just like a deep GSHP borehole is, but it still uses a heatsink method to draw relatively cool water (20C is cool in geothermal terms) to the surface to an exchanger that subsequently feeds a heat pump at the property.
Yes the geothermal wells we drill are targeting significantly higher temperatures, such that you wouldn't need to bother with a heatpump.Caerau Mines are 230m below.
A geothermal Powerstation goes to 1km to 10km.
So yes, the mine is heated by geothermal activity, just like a deep GSHP borehole is, but it still uses a heatsink method to draw relatively cool water (20C is cool in geothermal terms) to the surface to an exchanger that subsequently feeds a heat pump at the property.
Jambo85 said:
Yes the geothermal wells we drill are targeting significantly higher temperatures, such that you wouldn't need to bother with a heatpump.
Yes, you need a heat pump to 'condense' the energy from the Caerau mine, but none the less we are talking about constant geothermally derived temperatures of 20C (a warm spring day, in the UK). To compare it to a conventional Air- or Ground Source Heat Pump installation is absurd.Let's be realistic, guys: we're talking about a domestic heat pump installation on a 1990's house in the North East of Scotland, here, not a superinsulated and airtight Scandinavian cabin, or feeding it from a 20C constant heat source.
My parents own and live in a 1960’s built large 5 bed house in Northern France. The loft has been deeply insulated, the sous sol has had the ceiling insulated with about 12cm roughly of polystyrene type insulation, so essentially all the ground floor has bee. Insulated from underneath. Fully double glazed and a rating of C or D.
A room down stairs houses all the equipment with two condensers? Outside.
The house is always at 20deg.
The thing we notice are that the radiators never get really hot, I guess the fact it’s always on helps there.
They seem happy with it and they are two years in.
A room down stairs houses all the equipment with two condensers? Outside.
The house is always at 20deg.
The thing we notice are that the radiators never get really hot, I guess the fact it’s always on helps there.
They seem happy with it and they are two years in.
Edited by Simes205 on Wednesday 22 January 06:58
FranFran said:
Is there a minimum EPC rating, if someone wanted to consider ASHP in the future. I'm looking at houses, most of which seem to be rated C or D, and curious if this would allow/not ASHP in the future.
Not as an absolute rule, since EPC's don't tell you lots of things (for instance they give no indication of airtightness), but I think I'd be worried about specifying ASHP on anything lower than a current B rating.ETA: It also depends on patterns of usage. I've done lots of B-rated new-builds with EPCs, where customer satisfaction was poor, and running costs mediocre, largely because they were 'executive' housing where their occupants were out most of the day, but expected flexibility from their heating system when they were at home.
Edited by Equus on Wednesday 22 January 07:48
Equus said:
The basic shell of an early 1990's property will be very poorly insulated compared to modern standards; if it's masonry, it may still have an uninsulated cavity, which will be at best 50mm (twice that would now fail to meet current regs). It will almost certainly have been built with an uninsulated ground floor, and no attempt at airtightness.
There is a reasonable chance you are right, however that is a broad and sweeping statement. My parents house built in the late 80's has a 75 cavity with 50mm insulation, insulated flooring, mhrv and due to using conventional plaster probably as good or better air tightness as building half its age. A lot of this was uncommon, but certainly not unavailable.
wcel said:
I have the space to put in a horizontal GSHP system but I've been advised an ASHP is superior as it has less parts to go wrong, easier to sort issues, and will be cheaper overall.
I am not surprised the ASHP has cheaper installation costs, but I am slightly surprised from information based on my uncles GSHP install that it cant pay itself back after 20 years.We have an 245m^s E rating Edwardian house with solid walls and floor, currently on gas central heating, and it will be really interesting where we are in 20-40 years time with heating this. For now we have just made sure the rads are large enough to allow it ti run condensing and fitted a decent 'smart' thermostat.
Daniel
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