DIYbanter - View Single Post - Experiences with ground source heat pumps?

(NickIniquity) wrote in message

I've installed an air-to-water heat pump and I did a similar
calculation. In my case I wanted to use the unit to provide heating
in winter to a large outbuilding that I had insulated and converted to
a workshop. In the summer, I use the unit in reverse to provide
chilled water to cool both the workshop and the main house. (except
_this 'summer' obviously!) The heat-pump works out at about 330%
efficiency as it consumes 2.1Kw and produces 7Kw of heat output (or
around 6Kw of cooling). This was about the largest unit I could find
that would run from a single phase supply and match my anticipated
load...The short term start-up current is around 10Kw(!) which has a
minor lamp-dipping effect! In reality the efficiency will be lessened
because the unit has to periodically defrost itself to remove frost
off the outside air coils. Not needing to defrost is an advantage of
using a ground source heat-pump.

My house is heated by a gas-fired non-condensing combi.... on purely
economic grounds this is just about cheaper to run than the heat pump.
I wasn't too keen on extending the house c/h loop into the workshop
(effort factor...lots of digging and the risk of freezing), and I
decided that a heat-pump was a better bet than using an electric
heater. (and the temptation of adding a/c to the main house might
have been a factor here too). My workshop is divided into an
electronics 'shop and a general diy/woodwork area. As the heat
emitting device in the workshop is a fan-coil (water-to-air fan-coils
or UFH are the way to go with the lower water temp produced by
heat-pumps) this gave another advantage. I was able to make the
electronics end of the 'shop have a higher airflow than the wood
'shop...this results in no sawdust getting in the clean(er) area!

I went for air-to-water rather than ground source because I didn't
want to mess about digging up my lawn. Using a water loop for the
heat/chilling output side allowed easy diy installation of zoned a/c
into the house. Had I not wanted to a/c the house too, I would have
just installed a simple air-to-air split-packaged heat-pump to heat
the workshop instead.

Nick

Hi Nick,

Nice information. Thanks.
It is good to get real world information.

Roughly where are you geographically and can you give us more details
about the heat pump you installed?

Thanks,

Alan.