220 circuit. Can I make sub panel?

joppeltJune 11, 2012

A shed has a 220 outlet. (50 amp at breaker box in house.)

I want to put that into a sub panel in the shed, and then feed the original outlet with 220 with its own breaker, but also put a 110 20-amp circuit off that for lights and regular outlets.

Is this kosher?

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You need a 4-wire feed to connect a sub-panel, hot-hot-neutral-ground.

A 240 V load only requires a 3-wire connection, hot-hot-ground.
If the load was 120/240 V (and not a range or dryer) it should have a 4-wire feed.

Otherwise you need a new feed with 4 wires.

    Bookmark   June 11, 2012 at 5:49PM
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A lot depends on how the original installation was done.
If it is an underground feed to the shed:
The cable (or conduit) from the house must have four conductors: Two hots, a neutral and a ground. The neutral and ground must be kept electrically separate from the main panel to each load.
It must also be the correct type of cable (probably UF) or wires (THWN).
The size of the wire depends on the length of the run as well as the total amperage.

    Bookmark   June 11, 2012 at 6:00PM
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you will also need to drive a ground rod (or drive 2 at least 6' apart so you don't have to worry about ohms)

    Bookmark   June 11, 2012 at 6:15PM
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Thanks for the replies.

Actually, I don't know if it's underground or not. Shed backs to the house. It's all old work from a previous owner. And it's all enclosed in walls. My approach is to assume that the wiring is legit, and I was just wondering how to take what I had and wire up a circuit box to split off a 20-amp circuit for lights and outlets.

But it's a 3-prong plug, so I'm assuming 3-wire feed, and from what folks have said here, I can't feed that into a box and split something off.

All the other factors could be 100% perfect, but this makes the idea a non-starter, I guess.

And yes, I know I can run a whole new circuit to there. Other issues make that complicated.

    Bookmark   June 12, 2012 at 3:07PM
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For clarification, is this shed a detached building?

    Bookmark   June 12, 2012 at 3:21PM
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My question isn't about the shed. That's just where the outlet is. My question is about the outlet, and what I can (not) do with it. My question would be the same if the outlet were in my basement, or in my utility room, or in my bedroom.

And I think we've established that I cannot do what I want to do.

    Bookmark   June 14, 2012 at 9:58AM
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Your question might be the same but the location of the shed determines how to correctly and safely wire a sub panel. Electrical mistakes can have catastrophic and sometimes deadly consequences. The folks here just want to make sure you do it right so no one gets hurt.

If you don't have four wires a sub panel is out but you could re-purpose the existing 50 amp, 240V circuit into a single 20 amp, 125V circuit that you could use for lighting and general use receptacles. Would that help you?

    Bookmark   June 14, 2012 at 11:20AM
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And that's why it makes a difference.

    Bookmark   June 14, 2012 at 3:19PM
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Mike -- I was hoping to preserve a 240 outlet, just for future use. (AND have a lighting/outlet circuit tapped off of it.) That's why I was looking to put it to a sub-panel. But since it's not 4-wire, it's kind of all-or-nothing now on the sub-panel idea.

Without the neutral wire, how would I drop it to 125? Seems like I would have the same problem as the sub-panel (unless I rewire something at the current breaker box, I guess.)

    Bookmark   June 15, 2012 at 1:41PM
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For a straight 220 load you use a 2 wire with ground. The white is remarked black and used as a hot. In your case you will take the remarked white off of the breaker, mark it white and use as the neutral. The remaining black will go on a single 20 amp breaker

    Bookmark   June 15, 2012 at 9:24PM
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"My approach is to assume that the wiring is legit..."

NEVER assume THAT!!! In fact, assume exactly the opposite!

    Bookmark   June 16, 2012 at 7:17AM
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