Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
E
eaton
My unit coped very well at minus 5 in march, flow temp of 59c costing £4-5 per day. 21c inside, happy days, no back up needed or installed
G
Groundheat
Air to water units Can't compete with mains gas, all manufacturers will confirm this. They will however sell you a hybrid but this would never give you a payback. The hybrid takes the fuel prices and automatically chooses which to use . We have found that for the amount of time the air to water would be used for during mild winter weather it wouldn't save you enough money on your mains gas bill to justify having one fitted.They say sizing is most important, by this they mean insulation, if you first spend on insulation then this too would dramatically reduce your gas boiler run cost or oil cost.To save such a small amount it's not worth it, the average RHI domestic on an air to water would be around £500/year for seven years so the £3,500 would pay for the installation and once the seven years has gone you're back to paying higher bills because you can't offset them against your RHI income.
D
Dickie
Sorry jimbob no not one I've seen. I guess it's all down to the components.
Panisonic is good gear, but the Yanks are better than the Japs when it comes to AC in my view.
HTH
Panisonic is good gear, but the Yanks are better than the Japs when it comes to AC in my view.
HTH
Would one of these air source heat pumps be efficient with the overlay type of underfloor heating or is it best to run it with more traditional in screed type? Property was built early seventies so i imagine no insulation under screed. I dont want to dig the floor up really, so i suppose its a choice between the overlay and rads.
E
Ermintrude
U can use space blanket ££££££ but ufh always recommend a min screed of 65mm.
D
Dickie
The heatloss through the floor can be minimal, well, when there's quite a steady geothermal temperature that may explain why. Check out castellated insulation boards, they can be quite cheap & many you can just fit a chipboard floating floor over. Not ideal, but if you beef up the insulation in the walls & roof, it could be an option. Regardless, if fitting any ASHP I'd recommend some form of inexpensive supplementary heat; Multi-fuel stove.
G
Groundheat
Hi , we have been fitting overlay for around six years now, it's one of our best systems, the output is around 90w/sqm with a run temp of 45deg. Most suspended floor systems require 50-60deg which is too high for ASHPs , the problems we face with ASHPs is that when it's below freezing outside the ASHPs output drops so the higher temps are expensive to attain.
The heat up time is quicker than solid screed but the cooling down is quicker.
The ASHPs in temps below 0deg will go into defrost quite a lot. When this happens the ASHP stops supplying the under floor and reverses the hot water from the heating system around the evapourator to de frost it. This can take ten minuets so not only is the heating down for ten minuets it also robs your house of heat, once the ASHP re starts to heat then it will take 15mins or so to reach the temperatures it had before going into de frost, so the ASHP may only be heating for 35-40minuets in the hour. Not the sort of thing the manufacturers mention a lot although they now recommend fitting a buffer to overcome this.
D
Dickie
The general consensus is that an ASHP will work best with underfloor heating hence me thinking abut the overlay system, but i was worried about the thickness of the insulation. Those boards i looked at are only 20mm compared to the usual 50-75mm or whatever it is, dont want to fit it if its gonna cost a fortune to run. I have thought about maybe fitting rads and some insulation boards for the floor.
Its only a 2 bed bungalow, well insulated roof and cavity wall insulation, small garden though so definitely no room for oil tank or lpg, i would have had gas in a heartbeat if it was available.
I had thought about a wood burner, but i dont think logs are that cheap atm, and there is no chimney, so i think a flue in the living room woud look a bit naff.
Groundheat you talk about them perfoming badly below freezing, but eaton and a couple of others have posted positive results from their ASHP. Seems to be alot of conflicting info about this tech.
Its only a 2 bed bungalow, well insulated roof and cavity wall insulation, small garden though so definitely no room for oil tank or lpg, i would have had gas in a heartbeat if it was available.
I had thought about a wood burner, but i dont think logs are that cheap atm, and there is no chimney, so i think a flue in the living room woud look a bit naff.
Groundheat you talk about them perfoming badly below freezing, but eaton and a couple of others have posted positive results from their ASHP. Seems to be alot of conflicting info about this tech.
E
Ermintrude
Don't install cheap crap. The PV cells do have issues with dielectric and power drop off but that's because they are manufactured to within 0.0000000005mm tolerance in someone's shed in ahi zen.
Solar thermal is well proven and when done correctly will out last 15 year warranty.
Mitsubishi ashp tend to out perform. Bit like saying combi won't ever work........ Because all u seen is a fer falcon!
Solar thermal is well proven and when done correctly will out last 15 year warranty.
Mitsubishi ashp tend to out perform. Bit like saying combi won't ever work........ Because all u seen is a fer falcon!
Wouldn't say they would perform badly. But it is a limitation in the technology currently. The COP and output really begins to drop off in freezing temperatures. Which means it really begins to lose efficiency when you most need it. Hence why a decent auxiliary system would be preferable.
S
Scotsplum
Hi Guys ASHP vs Gas at present ASHP is an expensive option even with the grant, for UFH gas really is not an option unless you run the boiler at a lower temperature (unless you like dancing over floors as the floor will be hotter) but efficiency will then be rubbish. GSHP could be an option but again the installation costs could be bad. I am looking at other options one being the Newish Thermodynamic panel System (not sure if it qualifies for any RHI grant though because it works even at night but at present only for hot water).
E
Ermintrude
Blending valve controls temp of floor. U can have the flow into ufh at 100c if u wish and blending valve will keep floor temp within specified range.
Even with the RHI, ASHP's don't stack up against Nat gas.
Our advice to everyone is Insulate, Insulate, Insulate.
For an ASHP to get a CoP of >3 you need to run either ufh or rads at less than 45°, to run rads at that temp you need them to be sized 3x larger than normally required.
The gudelines on sizing heatpumps and emitters is both clear and comprehensive - you can download it all from the MCS website.
When you add in the costs of ugrading the rads it will never add up against Nat Gas, we are struggling to make a financial benefit to clients even when that are on oil.
For oil, the most sensible Green option is a Biomass boiler.
The RHI payments are open to anyone on or off gas grid - there are no restrictions, however they have been set at a level such that an effcient Nat Gas boiler will be the cheapest option, DECC are desparate to avoid a green rush away from gas, hence the payments are designed to make OFF gas grid people CONSIDER a green alternative when their boiler needs replacing, not as a wholesale green update. - They've learned from over generous PV FiT payments!
Also see this paper why buffer stores are essential on any form of heat pump (I now it relates to biomass, the same principle on sizing applies though)
ctc810-insights-into-biomass-heat-installations.pdf
Net effect you'll put an ASHP in to a on-grid property because you want to... however you need a CoP of much > 2.5 to really be greener than nat gas...
See here for the deemed CoP's at various output temps: http://www.microgenerationcertifica...y_Information_2_-_Heat_Emitter_Guide_v2.0.pdf
See this for the actual EST field trial results of ASHP's as installed : [DLMURL]http://www.energysavingtrust.org.uk/content/download/80377/973482/version/2/file/The+Heat+is+On+web.pdf[/DLMURL]
Our advice to everyone is Insulate, Insulate, Insulate.
For an ASHP to get a CoP of >3 you need to run either ufh or rads at less than 45°, to run rads at that temp you need them to be sized 3x larger than normally required.
The gudelines on sizing heatpumps and emitters is both clear and comprehensive - you can download it all from the MCS website.
When you add in the costs of ugrading the rads it will never add up against Nat Gas, we are struggling to make a financial benefit to clients even when that are on oil.
For oil, the most sensible Green option is a Biomass boiler.
The RHI payments are open to anyone on or off gas grid - there are no restrictions, however they have been set at a level such that an effcient Nat Gas boiler will be the cheapest option, DECC are desparate to avoid a green rush away from gas, hence the payments are designed to make OFF gas grid people CONSIDER a green alternative when their boiler needs replacing, not as a wholesale green update. - They've learned from over generous PV FiT payments!
Also see this paper why buffer stores are essential on any form of heat pump (I now it relates to biomass, the same principle on sizing applies though)
ctc810-insights-into-biomass-heat-installations.pdf
Net effect you'll put an ASHP in to a on-grid property because you want to... however you need a CoP of much > 2.5 to really be greener than nat gas...
See here for the deemed CoP's at various output temps: http://www.microgenerationcertifica...y_Information_2_-_Heat_Emitter_Guide_v2.0.pdf
See this for the actual EST field trial results of ASHP's as installed : [DLMURL]http://www.energysavingtrust.org.uk/content/download/80377/973482/version/2/file/The+Heat+is+On+web.pdf[/DLMURL]
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