UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

rhubarbe

We only have a 3 bed bungalow, circa 1933 (900ft2), and we only have an 8.5kW Ecodan, but I can tell you we're warm as toast. And it's only costing us half what we paid to shiver with LPG THIS TIME last year.

mitchy74

A big part of my problem is that I have planning for an extension that will take the house from 148sqm to 250sqm, altho the current half of the house might not be that efficient I am sure the other half will be significantly better, plus half the rooms wont be in use anyway and only need a minimal heat.

As it seems this RHI hasnt actually been set in stone I think (despite what the salesman said) I would probably be better spending my cash this winter replacing all the old Micropipe with the 15mm stuff as I think it is restricting the flow of my current system anyway and would probably stop any new system from being properly pressurised. While at the same time really doing my homework on exactly what I need, then get it fitted in the summer when there is probably a bit more come and go with the fitters price wise???

albyota

One thing is for certain, most decent heat pumps heat water to 55 degrees (apart from Sanyo ECO CO2, heats water to 65 Degrees, and Daikin Altherma HT, heats up to 80 degrees), and if the pipe work and radiators are sized correctly, then you get an efficient, warm, cost effective system. If you are stuck with microbore (advise replacing if you can), I would suggest using an ASHP with a thermal store, that way you can dump large amounts of heat into the store reducing compressor cycling, and run the heating circulating pump at its own flow rate.

rhubarbe

I'm afraid that I don't know anybody in Scotland, but from what you say 250m2 is pretty large - it's nearly three times the size of my house. As albyota has said, 14kW might well be enough for 90% of the year and some form of bivalency - your LPG boiler just to use on the coldest days.

There is no subsitiute for research..

rhubarbe

And from what I have read - albyota posts above - off peak electricity is cheaper in Scotland than anywhere else in UK due to hydro-electricity. Thermal store might well make sense in Scotland.

mitchy74

Definately intend to replace the microbore asap cost permitting but It will probably only be the downstairs as I imagine the upstairs wont be accessable without ripping up floors, its like spagetti under the ground floor and due to that easily losing a load of efficiency, there seems to be that much its nigh impossible to follow and could easily have a kink in it to. As said previously my LPG bill last year I felt was huge and the only time the house was ever cozy was when the log fire was on.

I had the same techy issues when replacing my boiler as I like to know as much about things as possible and when it comes to boilers/plumbing I just dont have a clue, the plumber probably landed me with a fantastic boiler that would work better than it currently is but is restricted with the crap pipe work as he replaced the bulk of the radiators.

mitchy74

rhubarbe wrote: »

And from what I have read - albyota posts above - off peak electricity is cheaper in Scotland than anywhere else in UK due to hydro-electricity. Thermal store might well make sense in Scotland.

I only have one rate at roughly 8p a unit.

albyota

mitchy, my house is timber frame, about 200m2 and an 8.5kW ecodan has been heating it for 3 years now.

Cardew

I would certainly agree that it simply makes no sense to try and specify a system that will cope with the 1% of days when the temp stays at, say, -5c all day. Just spend a few pounds on a couple of 3 kW fan heaters.

On the other hand you must not forget that heat pumps are at their most efficient with low water temperatures - which is where underfloor heating comes into its own.

Also bear in mind that with low temperature water in Rads/underfloor heating it takes much longer to bring a property up to a reasonable temperature than a conventional gas/oil CH system with the water heated to 80C+.

mitchy74

albyota wrote: »

mitchy, my house is timber frame, about 200m2 and an 8.5kW ecodan has been heating it for 3 years now.

So thats pretty comparable then, timber frame etc etc. Starting to feel like I avoided a very expensive mistake with Ice!

Not sure if I could upload floor plans etc, or if that would help in any way to the people that are giving me advice.

By the sounds of it though the independant survey and the micobore pipe are the first hurdles to pass? thankfully just got on to a 32.5ppl on the LPG so a bit nicer on the pocket than last year if its to be in another WInter.