Originally Posted by kok328
To the best of my knowledge a SPDT will cut both legs of power in a 2-pole circuit.
SPDT = Single pole double throw. Single pole means it only cuts on leg.
If you want to cut both legs you need a DPDT.Double pole double throw.
Not sure how the code feels on this but a normal three way switch could work. Put one hot on the common and the heater on one traveller and the AC on the other traveller. Only one device will be able to be on at any time.