240v to 120v

Len I'm a little confused as one of the things you also hafta do is wire it up to 120 v

Maybe you wanna use one of the 240-v phases but if so you hafta get a voltmeter 'cuz....well Eng why don't you explain about that 0.707 thing

If I read this correctly, what you want to do is reuse the wiring and replace the breaker on one end and the outlet on the other. If that is correct, yes you can do that, but you need to make sure you are using the right wires when you wire your breaker. As long as you verify that you have 120 to the breaker you should be ok.

Exactly what I want to do. There are 3 wires in the wall. I want to put an outlet there and change the breaker so it's a regular outlet. It's in a house with a 240v double pole breaker right now. I want to take that breaker out and put in a 120v single pole breaker. It's in a house so it shouldn't be anything major, correct?

Right. Wire is wire and doesn't care what voltage you put on it (unless you exceed the insulation rating which is not a concern here). Watch out for the breaker. A normal house has +120V, -120V and ground coming into it. (+ and - are relative terms since this is AC current. It means they are completely out of phase with each other.) Half of the house is wired +120V to ground. Half is wired -120V to ground. The 240V lines are wired +120V to -120V. You need to make sure you wire your new breaker correctly, ideally the same way other breakers on the same side of the box are wired. When it is all connected and turned on, use your volt meter to verify you have 120v at the outlet.

This should go without saying but just to be sure, the house power should be off when you are wiring breakers and you should either lock out the panel or have direct control of the master breaker.

Thanks engineer. Definitely going to kill the main power to the house before taking the panel cover off. And I know the two giant wires coming into the panel will still be live.

That is I was

Aha, Eng has you on the right track. It has occurred to me that if there are only two phases, it's gotta be 120 v each, not 0.707 x as with 3-phase