Electrical Question - 240v from 20a 120v line

[PonicalChillin]

Hey all,

Another 240v line in an upstairs bedroom is crucial for my next move. I've already got a 30amp 240v for the lights, but need another for a large AC.

I have a dedicated 20a 120v outlet nearby which was originally intended for an upstairs clothes washer.

Can I simply swap the single pole 120v 20a breaker in the basement to a double pole 240v breaker and just use the neutral wire as my other hot?

I havn't checked the wire size yet, but I'm assuming its 12 guage since its a dedicated 20a breaker.

Any confirmation this is safe to do?

Thanks,
PC

 

[pistolvania420]

I'm quite sure your gonna need a 12/3 wire to a 240v receptacle. Two hots, common, and ground. So your probably gonna have to fish a wire up there. Don't take my word for it though.

 

[PonicalChillin]

Thanks for the quick reply.

My 240v AC unit looks to only be a 3 prong so I'm hoping I can just obtain the 2 hots and a ground from the 120v outlet. 1 hot would remain a hot, my neutral would become another hot, and my ground would remain a ground.

peace
pc

 

[pistolvania420]

Your gonna need 3 wire up there maynne.

 

[zolar]

are you sure you won't need a 4th wire 240 V outlets i've open when moving boxes and wiring had 4 and more wires
but not always so ? red blue black white and green 4 ground
these sound familiar to the electricians on here??

some one posting the usual conventions on wire color codes for 120/240 volt wiring would help greatly...
i don't have a meter to go check a 240 v box and the differentt color wires but ....

 

[BeeBee]

I've done just what you are suggesting, with no problems. In fact, you can use the ground wire as your ground wire!
That's because 240 volt, 15 or 20 amp, three-prong receptacles are really no different than 120 volt receptacles--they only have three connections.
For 240, you have:
Hot (red buss), Hot (black buss), and ground.
For 120, you have:
Hot (red or black buss, depending on the position of the breaker in the box), Neutral (white buss), and ground.

Connect the black and white wires to the 240 breaker in the breaker box. Don't move the ground--leave it alone.
Then, connect the black and white wires to the two hot terminals at the receptacle--it doesn't matter which one goes to which connection. Finally, connect the ground wire to the ground terminal.
And you're done!