How to wire up a 240VAC receptacle

[Bratster]

I second the better Romex suggestion.

Get 10/3 w/gnd instead of 10/2 w/gnd.

Then you get you black and red for hot and a white for neutral. Even though you don't need the neutral now, it's not that much more money and is more flexible if needs change. Only $15-$20 difference in my area.

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[Spork Schivago]

Nice diagram.

If you are buying new Romex for this installation rather than using existing stock you might try to obtain cable with black, red and ground cores rather than black, white and ground cores. This will avoid the need to use black electrical tape.

Sorry for the late reply.   I've been almost dead for a few months now!  Docs think they know what's going on now, just gotta wait for a few more tests to come back.

Can I buy 10/2 with black and red instead of black and white?   I've seen 10/3 with black, red, and white....My wife already picked up the 10/2 (black, red, copper) I wanted the 10/3.   So we used heatshrink tubing for the white.   The inspector really loved that and felt that's how everyone should do that, so we earned some brownie points there!

[Spork Schivago]

I second the better Romex suggestion.

Get 10/3 w/gnd instead of 10/2 w/gnd.

Then you get you black and red for hot and a white for neutral. Even though you don't need the neutral now, it's not that much more money and is more flexible if needs change. Only $15-$20 difference in my area.

That's what I wanted, the 10/3 w/ ground.   I could have used all those wires, couldn't I?  Would it be wrong to have one of the neutrals going to ground the metal conduit box and the other ground wire going to the receptacle?   What I did, because I only had the 10/2 was run a pigtail off grounding screw on the receptacle, run a pigtail off the grounding screw on the box, and then twisted them together and used a wirenut to hold them together.

[6PTsocket]

Hello,

I have a device that has an IEC 60309 3-prong 32 amp plug.   It expects a 3-prong receptacle that has neutral, ground, and line.   Because I live in the US, how could I safely wire up the correct receptacle that has neutral, ground, and line, while still providing 240VAC and not violating the NEC?

I have single phase 120-0-120 coming into the house to the panel.

Thanks.

In the EU , from what I can gather, the 24O is between a hot and a neutral, plus a ground. In the US  the 240 is between two hots, with a neutral centered between them, plus a ground. Devices run on the potential difference between two points and don't care what their relationship is to the rest of the world. Connect the hot and neutral wires to the two hot terminals on an appropriately rated 240 volt plug and connect the ground wire  to the ground terminal. If you don't want to cut off your old plug you will need an IEC receptacle to make an adapter. Ground is ground everywhere so that is your safety. The only problem might be that your 50hz device does not like 60 hz. Transformers are to isolate or step voltages up or down. You already have the right voltage 120-0-120 is 240 volts between the 120 connections. Isolation serves no purpose here.

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[IanB]

Can I buy 10/2 with black and red instead of black and white?

I don't know, maybe not. You might not find it in a big box store, maybe you would have to get it from an electrical wholesaler. I haven't looked for it.

My wife already picked up the 10/2 (black, red, copper) I wanted the 10/3.

You mean black, white, copper?

So we used heatshrink tubing for the white.   The inspector really loved that and felt that's how everyone should do that, so we earned some brownie points there!

You put red heatshrink on the white wire? That's fine. You could also use a wrapping of red electrical tape.

That's what I wanted, the 10/3 w/ ground.   I could have used all those wires, couldn't I?  Would it be wrong to have one of the neutrals going to ground the metal conduit box and the other ground wire going to the receptacle?

Here I am confused. Neutral (white) is not ground (bare copper). The neutral wire has white insulation on it to indicate it is a live (current carrying) conductor, and must never be allowed to touch bare metal parts.

What I did, because I only had the 10/2 was run a pigtail off grounding screw on the receptacle, run a pigtail off the grounding screw on the box, and then twisted them together and used a wirenut to hold them together.

Again, confused. You had 10/2 cable with black (L1), white (marked red, used as L2), bare copper (no insulation, ground wire). The bare copper wire shall be connected to the ground screw on the receptacle, the box, and any other metal chassis parts. Pigtails may be used for this as necessary. Under no circumstances shall a bare copper (ground) wire be connected to a white (live) wire.

I do not understand why you say "because I only had the 10/2" ? Your 10/2 has a bare copper ground wire to connect to ground screws. Where was the problem?

[oPossum]

My wife already picked up the 10/2 (black, red, copper) I wanted the 10/3.

You mean black, white, copper?

black/red/bare is used for NEMA 6 and L6 series receptacles. They have L1, L2 and ground. No neutral.

[IanB]

black/red/bare is used for NEMA 6 and L6 series receptacles. They have L1, L2 and ground. No neutral.

Sure. But please look at the context:

Can I buy 10/2 with black and red instead of black and white?   I've seen 10/3 with black, red, and white....My wife already picked up the 10/2 (black, red, copper) I wanted the 10/3.

Given the context, do you now understand my question?

[oPossum]

I don't really understand any of your questions. I don't think he did anything wrong, and it passed inspection.

[IanB]

I don't really understand any of your questions. I don't think he did anything wrong, and it passed inspection.

Please. Spork asked, "Can I get cable with black, red and copper cores?" And in the very same sentence he said, "My wife bought some cable with black, red and copper cores."

Why ask that question if it is already answered?

So given the context of everything else, I think that was a typo. I think his wife bought cable with black, white and copper cores, and then when he installed it he put red shrink wrap over the white insulation to mark it as a live wire.

[6PTsocket]

You haven't been told you can't use NM-B to wire a fixed circuit from the breaker panel to a wall outlet. You can. That's why an electrician is able to do so and have the work pass inspection.

You keep getting hung up on "hot" and "neutral". But a circuit has two wires. You can think of them as "out" and "back". Whatever current flows "out" has to flow "back". 20 amps out, 20 amps back. The current in the two conductors is always equal and balanced. That's why you can't add up 20 and 20 to get 40.

You can work out for yourself why two 120 V, 20 A circuits do not add up to a 240 V, 40 A circuit. Think about it. 120 V x 20 A = 2400 W. Therefore 2 x 120 V x 20 A = 4800 W. But 240 V x 40 A = 9600 W. And 4800 W does not equal 9600 W. It doesn't add up.

If your load draws 30 amps then the "out" wire has to carry 30 amps and the "back" wire has to carry 30 amps, and each pole of the breaker has to carry 30 amps.

Two 120 v circuits do add up to 240 if they are coming from the two legs of a 240 feed and not the same leg. Either hot to neutral is 120. Hot to hot is 240.

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