Originally Posted by soundgodjr
IMO, the GFCI will still work with a 3 wire feed IF and only IF your neutral is bonded to ground in the breaker box. I know this because I tried it on my 3 wire feed and it tripped while I was draining my kettle into my sink. I live in an apartment and it seems there is enough current in the water pipes to trip the GFCI!!! This was after I had grabbed the faucet and the kettle at the same time and felt a little jolt!! No bueno!
I can confirm it works like this. Just moved houses, only have a 3wire outlet with no ground run through the wall.. If the neutral is tied to the ground in the panel, you can tie the neutral to the ground before the GFCI, and it works. Word of warning, you can't use the neutral as a return, so you can't hook up anything within your box to use 120v. It all has to be 240.
It's not ideal, nor to code, but ya...