(Not an Electrician) I have a 220V air handler (not part of the HVAC system its for a homemade wind tunnel) that I need to get power to. There is an old dryer receptacle (10-30R) in the basement that I'd like to use. My plan is to use L1 and L2 to power the air handler and connect the white wire to the case of the air handler like it would have been in an older dryer. I know that this wouldn't be to code but my question is about safety. How big of a risk would I be taking and what horrible things could go wrong?
The fact of the matter is that 99.9% of all electric clothes dryers and electric cook stoves in USA operated under these very conditions from the time of the WWII until the very late 20th century. At that point America was ready for another layer of safety. Does the 4th wire make it safer? YES. As long as the neutral wire never comes loose from the neutral bus bar and all other connections remain clean, tight and dry you are relatively safe. Would I do this in my own shop? Probably. Would I do it around children or family conditions? NEVER!