30amp, 220V wiring question

[barnesrich]

Hi All.

I have a 30 Amp, 220 volt recepticle to power a shop heater (which lists these requirments). Ive purchased 10-3 wire for this (though im thinking 10-2 would be sufficient as well).

The 30 recepticle I bought has 3 poles on it to hook up the wire (2 hot, and one green - neutral).

When I wire to my 30 amp breaker, I have 2 hots coming out of the breaker which would go to the 2 hots on the recipticle. I'll run the ground from the breaker box to the green ground on the recipeticale.

What Im confused about:

With 110 15 amp I run one hot from the breaker, one neutral (white) and one ground (copper). But where does the white go when im hooking up the 220? Theres nothing for it on the recepticle, so I guess it isnt used?

Any help or explanations would be appreciated!

Thanks!

[CJT]

Enlist qualified help. Methinks you have some serious misconceptions about what's needed.

[zxcvbob]

You only needed 10-2 cable.

Connect the black and red wires to the breaker and the green wire to ground. You have 2 choices with the white wire, and I'm not sure which is better (I don't think it really matters): In the receptacle box, tape or wirenut the end of the white wire and don't connect to anything. In the breaker box you'll either connect the white wire to the neutral buss or leave it unconnected and tape/wirenut the end. Don't cut the white wire short at either end, you may need it someday if you ever need to hook up a 240/120 device, like an electric clothes dryer w/ a 4 prong cord.

Best regards, Bob

[RBM]

You are correct, if it is a straight 30 amp 240 volt outlet, you only need the three conductors. If you used 10/2, you would connect the white and black to your breaker and the ground to ground buss. In your case you don't use the white/neutral as you don't have one on the receptacle. Some devices require both a ground and neutral, in which case you'd have a four wire receptacle

[Bob Vaughan]

And if you use 10/2, with white as a hot lead, you need to re-identify it by taping it with colored tape (red is appropriate, but it could be any color other than white, green, or grey).

[barnesrich]

Thanks - This is exactly what I did.

10-2, color taped the white lead at both ends to indicate its hot. Checking the coltage indicates to me ive done things correct - each hot to ground reads 110v giving me 220, correct?

[Toller]

Each hot to ground should read 120v. If it actually reads 110v you have a problem of some sort. Did you test hot-hot? It will be 240v if you did it right, and 0v if you did it wrong. Yeh, its tough to do it wrong, but stranger things have happened.

I would have used 10/3. You don't need the neutral now, but it is very possible that in a couple years you will need a 240v circuit with a neutral and will regret saving the $1.50.

[barnesrich]

Sorry, yes it reads 120v. No, I didnt test the hot to hot, but thats good to know - ill confirm thats 240.

Out of interest, what would be the cause/reason of hot to hot reading 0 volts? It seems like if each hot to ground reads 120, then the hot to hot would *have* to be 240?

As for 10/2 vs 10/3 - what youre saying makes sense. However this outlet im mounting 3 feet from the fuse box for heat while I drywall. Ill need to decide where I want to permenatly put the switches, in whcih case ill do it with 10-3.

Thanks for the help.

[Dave Hammond]

I had to do something similar to this a year or so ago, I ran 10-3 for the exact reason you listed. Boy am I glad, saved me some time down the road not having to rip/replace, just take the wire nuts off the unterm'd neutral and connect.

Dave

Toller wrote:

[Toller]

You would really have to screw up to do this, but if you took both hots from the same leg of the box, then they would be zero between them; and you would get no heat.

I found someone had done that on a multiwire circuit in my house; luckily they were lightly used circuits or they could have started a fire easily enough.

[Steve Kraus]

What if a neutral is needed? Is it permissible to have the third pin be neutral (as was done for many years HOT-HOT-NEUTRAL no ground) or does the Code now require 4 pin receptacles? Neutral is needed on equipment where some components are 120V.

The standard 240V/30A clothes dryer outlet had three pins using a neutral, and yep, the frame was "grounded" with the neutral. Seems astonishing but that's how they were and in many cases still are.

[Chris Lewis]

According to Steve Kraus :

The OP appears to be putting in a construction cube heater. That's a pure

240V load (two hots plus ground). Neutral is not required, and should not be ued.

Since he's already bought 10/3 wire, he should wirenut both ends of the white without connecting them to anything.

But they're not allowed to be done that way anymore.

[Stormin Mormon]

I'd suggest you hook the white to the neutral bar in the panel, and to the ground at the heater. That way, you've got two wires supplying power, and two for ground if the whole thing shorts out.

[Chip C]

Urk. The green connection is not neutral, it is ground, and should only ever be connected to the green or bare ground wire in your cable. This comment is probably what red-flagged your posting for the "seek help" response. (Purists might also argue that a "pole" is only a current-carrying terminal, but I'm not so sure about that.)

As others have already posted, the white in your 10-3 cable is superfluous for this outlet and should not be connected to anything in the outlet. However, I agree that it's a fine idea to pull the 10-3 in case you ever want it.

Chip C Toronto

[SQLit]

This is your idea of doing good work?

The NEC expressly prohibits paralleling conductors below 1/0. The neutral and grounded conductor(s) can only be connected together at the service. Any other intentional connection is a ground loop and ooops expressly prohibited by the NEC.

Me hopes your being sarcastic

[Oscar_Lives]

I suggest you say a few extra prayers to that comet god tonight. If this is how you wire things, you are going to need all the help you can get.

[Jake]

I dunno where this post came from... maybe I've lost track.

I'll say this ONE MORE TIME for all that can read: DO NOT.. EVER... GROUND a NEUTRAL ANYWHERE but at the panel where power comes into the building (called a service entrance). Anything else can get you electrocuted. Elsewhere, grounds go with grounds, neutrals with neutrals, hots with hots.

To the OP.... if your heater is 240 volts and does NOT require a neutral, then your receptacle (notice spelling) needs two hots and a ground, wired to a appropriately sized two pole breaker. If you don't know what this means, you need to hire a electrician.

Jake

[Stormin Mormon]

In this application, white and green are grounds. Not designed to carry current in normal operation. 230 volt heater doesn't have a neutral.

Thanks for the head up about the code.

[Stormin Mormon]

Dear Jake, the OP has a 230 volt heater. Two wires black and red for power. And no neutral. Thanks for the very wise counsell about grounding a neutral. I'll remember that if I'm ever working with a current carrying neutral. Actually, I did take a rap off a neutral once. I'll tell you about it, if asked.

[Steve]

What????? I hope to hell that's your idea of a sick joke not how you would actually wire it.