Andrew wrote:
On 03/04/2021 17:15, George Miles wrote:
I was thinking if i ever get a Air Source heat pump
then maybe have the inlet pipe in the cellar?

Because in the winter the cellar is warmer than the house,
- it gets heat from the earth.

Is this a good idea or daft?

You will simply make the cellar colder and then heat will
transfer from the house.

Sounds like an excellent way to make a walk-in freezer, but won't do much
for efficiency or heating the house.

If you had any land then installing at one end of a closed
polytunnel might work too, but if you had any decent land
then a ground source heat pump might be a better bet,
depending on your location and soil type. Nice sticky
clay is best (AFAIK).

You need about 1m3/second of air flow, and if any of that is not at ambient
temperature then efficiency will nosedive. So a polytunnel is unlikely to
work, especially when overcast or at night, This is also why installing a
duct from the outside to an ASHP in the cellar is unlikely to work unless
the duct is ~0.5m across.

If you have the land ground source is generally more efficient, although
there are issues if you take out too much heat in winter that the land
doesn't recover in the summer, so the loop needs to be properly sized.

Water source is best, if you have a lake or river available.

Theo