pat_os said:
I'm looking at putting in a gshp in a new build but am wondering whether it would be better to go with the vertical or horizontal collection method. The vertical is presumably more efficient but more expensive to install but I'm wondering how much more expensive it is. If the horizontal pipes are going to require a digger and driver at ~€30 an hour for a week and the grant for the vertical is 2k more than for the horizontal then would it be worth my while going for the vertical
Pat,
I was originally all set to go with a horizontal collector when I just
by chance happened to ask a chap locally about his house build and
heat system choice. He told me that his plumbing expert advised
against GSHP for his site on account of the type of soil (gravelly,marl,
etc). I invested a couple of weeks checking the issues and what
I have found is that amongst the most reliable folks in the know
there seems to be a consensus that horizontal collector is very
sensitive to the soil conditions and because of that one needs to
be wary of installers/suppliers who de-emphasise site survey to
advise on ground conditions before giving the choice of horizontal
versus borehole.
The horizontal collector relies on a sort of replenishing conditioning
of the ground by rainwater/moisture and the heating of the upper
layers (within the first meter to meter & half) of soil.
The "marly" soil it seems loses the moisture conditioning too fast
to boost thermal conductivity of the soil and the other extreme
is if you have very poor drainage as a result of stagnant water.
The latter scenario is very bad news as you have risk of ground
freezing up around collector area.
It seems there are ways to counteract the first case .. eg,... importing sand
and creating drainage channels.. but when you add the cost
of excavation, sand import, drainage channels, refill for such a
wide area of ground you might be well worth exploring the borehole
option now that the grant is available.
My current plans are borehole .. and if the drilling isn't feasible
I'm going to look at wood pellets ... or a condensing oil boiler
(option 3).
-ipxl