There are also outlets used for room air conditioners. I have a 120V
15/20A outlet by one window downstairs and a 240V 20A (IIRC) outlet
for the thru-the-wall AC. Stoves and clothes dryers may also have
either a three pin ungrounded or four pin grounded outlet.



I've heard of those, I don't recall ever actually seeing a 240V window AC
unit though. AC in general is very rare around here and if people have it,
it's normally central. Perhaps 0.1% of the houses have vertical casement
windows that an AC unit will fit in, I suppose that would explain it.