Electrical Question

[Scott Greaves]

Hey Creekers! ;-)

I need to hook up one of my 240v receptacles so I can play with my new lathe (not that new - I told about it over a month ago!).

Anyway, I finally have power to the shop as of last week, and I've hooked up a couple of 110v receptacles for odds and ends, but will wait on all the rest for when the insulation and wall coverings go in.

The receptacle is a NEMA l6-30. I wired the 240v circuits with 10/3 nmb /w ground, so four wires into each box. The receptacle has only three screws, so which wire gets left out? What, if anything, should I do with that wire (and I don't need any wise answers about sticking it anyplace! :D ).

Thanks in advance!

Scott.

[Bill Howatt]

Scott,

240V is obtained between the 2 hot wires, typically a black and a red. You should be able to see each of these wires connected to a double circuit breaker in your panel.

The white is the neutral and you will measure 120V between it and the red and it and the black. For 240V only operation, this is the wire you don't need. Just cap it off in the box with one of the plastic insulating caps.

The fourth wire will be the safety ground and should be connected to the box and (very likely) the receptacle. The ground screw on a receptacle is usually slightly different in appearance and has a green tint to it. It is probably near the bottom of the receptacle ( I don't know what your receptacle looks like so I am talking in general terms). This safety ground wire will either be bare or green.

Hope this helps, but if you aren't sure don't connect it - get somebody who knows electrical stuff to help you!

Bill

[Scott Greaves]

Hi Bill,

You confirmed what I thought. The receptacle is a Hubbell 2620, and I knew it needed the two hot wires. The third screw is green tinted like your normal ground, but I didn't really know what I'd do with the left over white. I'll cap it like you say. Thanks!

Scott.

[Rob Russell]

Scott,

FYI, you didn't need to run 10/3 for your receptacle, all you needed was 10/2. You'd just mark the (2) ends of the white conductor with red (or black) tape to indicate that it's a hot current carrying conductor.

If your box was metal, you should ground that as well. You can get green grounding screws at any big box - there's a prethreaded hole for them. "Pigtail" the (3) separate grounding conductors (1 from receptacle, 1 from box, 1 in the NM cable) together with a wire nut. The Hubbell 2620 is a "self-grounding" receptacle (nice choice, btw) but I like to guarantee the grounding to the box by installing a conductor directly to the box. That way a loose receptacle doesn't compromise the equipment ground connection for the box.

Rob

[Scott Greaves]

Hi Rob,

Thanks for the info! I had originally planned to use a NEMA L14-30 receptacle - what would that be, a 2710? By the time I decided I would go with the 2620 I already had a bunch of the 10/3 wire, so I used it anyway. Hubbell makes such nice receptacles! I think I will use them all the time now. By the way, I bought all of the Hubbell plugs and receptacles off of Ebay for about 1/5th of what they would cost normally! Less than what you would pay for Leviton at the local HD. The idea of grounding to the box is great! But I went with plastic boxes, so I guess I won't! ;-)

Thanks so much for the information!

Scott.

[Rob Russell]

Originally posted by Scott Greaves
I had originally planned to use a NEMA L14-30 receptacle ...


Scott,

In one way, it's too bad that you didn't stick with the 14-30 configuration. That would have given you a neutral and meant you could run 120v loads in conjunction with 240v loads. For example, a 240v bandsaw that has a worklight on it or a router table built into your table saw would need the extra conductor.

Rob