Air Source Heat Pumps

richardc1983

bludger wrote: »

Richardc1983,



I haven't thought about air to air, probably because of the lousy embedded system that a relative of mine had back in the 80's. Huge gizmo in the kitchen and ducts under the concrete floors with vents coming out at odd places. It was a new semi built on a estate by a cheapjack builder. Horrible. The system was gas fired now I think about it.

Many thanks,

Air to Air is what you was describing above with the fan convectors. Its the same thing. Its just known as air to air.

You dont need huge ducts any more, its a unit that mounts on the wall and a 3.5kw unit is smaller than a 3.5kw double radiator.

paceinternet

I've been reading about central heating using fanned convection heaters. These use very low volumes of water which need to be heated to a lesser degree than normal radiators because of the fanned air distribution.

richardc1983, there is a difference here to what you have. Your air to air has the refigerant piped to the fan coil units.
bludger describes the system having the water going through the fan coil units. This could be heated or cooled water from the heat pump (cooled water is not available from all heat pumps).
The advantage of using an air to water heat pump is that you could use a mixture of underfloor, radiators and fan coil units. Plus, you do not have to be involved with refigerant piping to the fan coil. It is all done internally within the heat pump system. Monobloc units have no external refigerant piping. Although some heat pumps have a second unit internally for exchanging heat from the refigerant to the water, you still pipe water to the fan coil.
Companies like Myson and Smiths who make fan coil units, are now quoting outputs at lower water temperatures for this purpose.
As Albyota says, some can be quite large. They need to be bigger at lower water temperatures, the same as radiators.

richardc1983

Ah thanks for pointing that out Albyota. Sounds like a good system, I would certainly go down this route and have warm air as the warm up times are much faster than underfloor and the system is more responsive. You also benefit from the cooling in summer.

nethertonhall

paceinternet wrote: »

Presumably you recognise the "up to" bit of the spec as also in the previous reply.
So, is the issue about "how do I achieve the maximum quoted COP"?

Did they discuss the output temperature settings with you? They must be able to say that at ground temperature of x and hot water inlet or outlet temperature of y, it will give you COP 4. If so, have you run it under those conditions?

You must know that if you are running it at less than x and more than y, the COP will not be as good.

They have specifically agreed that the 800m loop installation is acceptable?

The up to bit - this is what they are now publishing on marketing material / web. My quote clearly stated I would get 3 freee units out for every 1 in - for a life of 25 years. My solicitors have said it is very clear!

Temeratures have been discussed and trials run (we have never seen the 3 units out) but, the above statement had no link to these. - I understand these effect the COP and Danfoss did not misrepresent this figure.

The ground loops were all sized by danfoss and commisioned by one of their approved installers.

I accept, the system is great the house is warm - but at the end of the day I am getting out less than their claim! This relates to a substantial sum over the 25 years.

Others must have had similar statements claimed.
I can support the post with documents if this helps.

paceinternet

Hi, nethertonhall, whilst I sympathise with you if that is what you based the investment on, it looks as though Danfoss made an error in their quote. Interesting COPup maybe?

A COP of 4 is very possible with some systems (I don't know about the Danfoss model), but it is very unlikely any supplier would quote that number as guaranteed 24/7/365/25years. Or it would be conditional to ground conditions and your water temperature settings, which you may not be able to comply with over such a long period of time.

Cardew

nethertonhall wrote: »

The up to bit - this is what they are now publishing on marketing material / web. My quote clearly stated I would get 3 freee units out for every 1 in - for a life of 25 years. My solicitors have said it is very clear!

Temeratures have been discussed and trials run (we have never seen the 3 units out) but, the above statement had no link to these. - I understand these effect the COP and Danfoss did not misrepresent this figure.

The ground loops were all sized by danfoss and commisioned by one of their approved installers.

I accept, the system is great the house is warm - but at the end of the day I am getting out less than their claim! This relates to a substantial sum over the 25 years.

Others must have had similar statements claimed.
I can support the post with documents if this helps.

The 'up to' statement is the 'get out of jail' clause for most companies.

If your quote stated an effective COP of 4, without any qualification, then you clearly have grounds to make a few more solicitors rich!!

I would have thought that the company would offer a 'without prejudice' settlement.

nethertonhall

Thanks Guys - The quote clearly states You will get 3 free units of energy for 25 years - I could not believe it when I read it but! The sales guy who did the quote / deal has long gone from Danfoss.

We are in discussions with Danfoss about a settlement, at the moment we are a long way off - but we will keep talking.

Thanks all for your help - Danfoss have now changed their quotes which covers them and is fair going forward.

For me - I may as well have a go!

Swipe

I'd be interested to know how much is it costing you to run it per winter quarter

nethertonhall

Hi Swipe, our electricity bill was £90 / month prior to installing the ground source and now its £200 - £230 / month (very cold winter) This will drop during spring / summer and autum.

Prior to this we had oil heating.

Hope this helps

albyota

Netherton, my electric consumption went up from £380 per year to £837 per year in four bed house, however my oil useage has gone from £900 ish to £0
you have not mentioned how much oil you used to use.