Jules Richardson wrote:
On Thu, 25 Mar 2010 13:27:12 +0000, The Natural Philosopher wrote:

Jules Richardson wrote:
On Wed, 24 Mar 2010 15:36:11 -0700, wrote:
http://en.wikipedia.org/wiki/GSHP.

The initial costs are considerable though
Where are the costs, though? The way I understand it, it's mostly in
the labour involved in installing the ground loops - which, given the
nature of this group, *could* be handled by the home owner.


thats nothing you can do yourself in a couole of days with a mini
digger.

*exactly*. Frost line's pretty deep around here though, so I'd probably
be looking at putting loops 8' down or so - but it's still just "grunt
work".

Problems I have he

1) Knowledge Commercial installers seem to have the market pretty
well sewn up, and there's comparatively little design knowledge in the
public domain,


I di a load of reserach.

teh main costs were not in the ground loop - I coudld easily do that
myself, and the people I spoke to were almost relieved that I would,
but in te heat pump units themselves - at leats 5-6k, and probably more

Ouch. What's the reasoning for the cost?


No idea. Lack of economy of scale I suspect.


I went through this with wood-burning furnaces, which are similarly
expensive - and there's really bugger-all to them. The cost seems to be
just down to "that's what the market will take", rather than something
that reflects construction time and materials costs. Heat exchangers for
GSHPs may or may not be different...


same rules. Not enough of them, no real thought to cost reductuion,
madee by hand somewhere..usually Germany or Sweden..

and in the electricity supply - they really need a massive amount of
startup power even on soft start units. In fact the guyt never did get
back to me to explain why a 15Kw unit at an alleged 4:1 step up of input
power to heat out, needed a 25Kw supply.

Extra ouch :-) I'm not sure if our place would take that or not. We've
got about 14Kw of electric heating at the mo, but I don't know how much
spare capacity there is.


Im fused at 100A, so 25KW is my peak draw.. capability. Realistically
they don't draw that for any time at all. Like fridges most of the time
the compressor aint on.

2) My 'leccy company gives a huge discount for having a GSHP, but only
if it's a commercial system fitted by 'professional' installers,

therss always a catch.

Yep. No doubt their list of approved installers all charge 30% over the
going rate anyway...

3) I can get tax breaks for a GSHP, but hit the same problem as in 2
above.
I have always found that any government grant costs precisely as much to
achieve as it pays back, within 10%, every time I have investigated one.

Certainly seems the way for 'big stuff'. It's not so bad over here for
things like installing energy-efficient doors and windows; I can do that
myself and just wave a receipt for the materials under their noses and
they seem to be happy.

Retrofitting is not really an option. Its rip out, redesign and replace
just about all the pipework and heating system.

It's not so bad at our place for the ground floor, because the basement
(almost) covers the entire house footprint and isn't finished (yet - it's
on my to-do list for this year), so I can easily get at the underside.
The top floor would be more tricky, though (although to a certain extent
I could rely on heat rising up from the floor below)

Also note that if your ground goes below -5 at deep levels, it may not
work at all.

Yes - I meant to bury a few temperature sensors before winter hit, but
never got the tuits together. The water we get out of the well sits at
around 55F year-round though, which is promising - but the depth of the
frost line over here makes things a bit more challenging.


Right. That is encouraging.

The fact that you can pump it in winter at all, means there is stability
till quite near the surface.

In the UK frost doesnt generally reach more than a foot down. And that's
unusual.

1-2meters is the recommended pipe depth. two meters is a bigger than
mini digger, but its still a trivial trench with a decent bucket on a
3-5 ton machine.




Using bores rather than trenches for the loops would be better, perhaps -
but there's no way to DIY that, so it's back to enormous costs again...


No, not if you have the space. soggy ground is best. a meter down in a
peat bog is the sort of thing to aim for, and anyway, you have very hot
summers, so you should be starting from a decent level anyway.



cheers

Jules