Post by Jimmy Wilkinson Knife
Why on earth could an AC unit not run backwards? You just reverse
the pump. Every one I've seen in the UK (commercial and home) has
been able to do this. The controller usually has settings for
heating, cooling, or automatic. On automatic you can simply set a
range (say 18 - 22C) and if it goes over, it cools, if it goes under,
What you're describing is what is referred to a split unit system or
inverter. After screwing around with a through the wall A/C unit which
was noisier than all get out in the size needed to cool the addition, I
finally got smart and picked up a split system (air handler inside,
compressor/inverter outside). What a difference. Very quiet (hard to
tell it's running, actually), and much cheaper than our old A/C unit.
And, as you say, when heat is needed, the system reverses itself and
heats the interior drawing heat from outside even when it's in the 20F
degree range outside.