When I drove my Bolt to my sisters place and needed to charge over night, she said, "no problem, we have a 240V outlet in the garage from when we had an electric water heater"... when I got there and looked at the outlet, it looked melted.... so I made sure the breaker was turned off, made sure it was dead with a multi meter and disassembled it. The wire ends at the breaker looked like they were in perfect condition, and the wire ends at the outlet were fine, but the outlet itself looked like it had an internal fault that caused the damage. I replaced it with a new outlet, and used my "home built" 240V extension cord coupled with an adjustable amperage L2 EVSE set to 24 amps and everything worked out fine. If I didn't know how to do wiring I would have been SOL though!
Keith
PS: I always recommend a stout 240V extension cord (mine is a welding extension with different plug and socket attached) when charging at a relatives house off of their dryer plug... it is seldom in a convenient location for plugging in the car.