Plug is three-pronged, as in
- |
O
Does this type of plug have a name? A/C-heater has no thermostat, looking for a plug in timer.
Is it 120 VAC (NEMA 5) or 240 VAC (NEMA 6)?
NEMA “5-20P” plug
Does it look like that? If so, then it’s probably a 120 VAC / 20 A plug. It can only be plugged in to a NEMA 5-20R receptacle.
AS for a timer, not sure. Am googling…
If you are trying to draw what I think you are trying to draw, it’s a NEMA 5-20P. More people will know what you are talking about if you just call it a 120 volt 20 amp plug though.
ETA: Ninja’d.
Grainger has a nice selection of timers. The INTERMATIC 20XE85 is rated for 120 VAC / 20 A.
Keep in mind, though, that “hot switching” can be hard on the timer’s switch/relay contacts. In other words, while the switch/relay contacts may indeed be rated for a continuous current of 20 A, opening or closing the contacts under full load can cause arc erosion. An appropriately-rated RC snubber across the load or contacts can help minimize the erosion. A better (but more costly) solution is to use a timer that drives a SS relay with zero-crossing feature.
note
20XE85 is the Grainer vendor part number.
HB113 is the INTERMATIC manufacturer part number.
Good catch. Thanks. 
OP needs to be very sure what this is, since NEMA 6-20 (250 volt) is the “reverse” of the 125 volt 5-20; the 6-20 swaps which blade is vertical and which is horizontal.
