Chris J Dixon wrote:
Fevric J. Glandules wrote:

Can a heat pump (i.e. air conditioner
in reverse) work in sub-zero temperatures? Won't it just
ice up horribly?

I have had them at work. Yes, it does ice up, so the control
system runs it in reverse for a while - it melts the ice, but
blows cooler air indoors. On balance it seemed to work, though it
might be less comfortable in a smaller space.

Chris

I have one in the workshop. They work well apart from 0 to 4C. The
efficiency drops off below freezing but it keeps the place at a nice
healthy 26C IME. The AC is useful in hot weather, a couple of days a
year. Very painless to operate.