On Jun 22, 6:01 am, harry wrote:
are a bit useless, as when you need most heat, they work less well
and at about minus 5, pack in altogether. This down to the
refrigerant gas used.

However there is a new technolgy one out now, runs on CO2 refrigerant
and works to much lower outdoor temperatures. Sanyo.

http://www.airconwarehouse.com/acata...O_Brochure.pdf

Seems to me that a DIYer could make a heat pump by just compressing
air inside and letting it expand outside.
It doesn't even have to recycle the air - just get some fresh air.