So I currently have a hard-wired 240V heater in my garage:
Though I don't use the heater often, I'd like to have the option to use it so my thought was I could have a 3-way switch that would switch on power to one or the other, never both. Is this possible?
The 240V heater is on a 30amp breaker and is rated for 30amps so I'm pretty sure the wiring from heater to panel is to code.
In the photo you can see there is a switch to optionally cut off power to the heater and I thought that this could be replaced with a 3-way switch that could either be off, power hard-wired heater, or power a 240V EVSE receptacle that would have to be branched off of the box. For the receptacle, I was thinking since my charger can be optioned with a NEMA 6-30 plug, that a NEMA 6-30 receptacle would be correct since there's only 3 wires from panel to heater (to my understanding a NEMA 14-30 would require a fourth wire to be run from panel to box).
Best Answer
Simplest option would be to change the heater input to cord&plug, and put the receptacle required on the wall, and plug in one, or the other.
For a fair amount of money as switches go, you can get a 30A rated DPDT (douple pole double throw) center-off switch that does what you ask. The one I could find was in the "very beefy standard switch" look and may be similar to what you have (Presumably DPST) if it's properly rated for the load. The one I found was rated for motor load disconnect use.
You may also be able to find that function in a "gray box on the wall with a big handle" format, but I struck out (I found plenty of disconnect switches, which are single-throw and don't do what you need.)
If you want to completely overcomplicate it (but it might actually cost less) there is the "use a contactor relay" method mentioned in comments. It strikes me as overcomplicated, and it might also be code-dubious as you'd be assembling a system from recognized parts (we hope - beware of Amazon, etc. for this sort of product,) rather than using a directly listed product.