[Metal Manipulator]

I need to put in a 220 receptacle for a plasma cutter, it calls for a 20 amp circuit breaker so what gauge of wire should I use between the breaker box and the receptacle? It will be somewhere between 2 feet and 8 feet in length.

[Demented]

12AWG Copper or 10AWG Aluminum. Can handle 25A at up to 80' so it'd be more than good.

[Mike Westbrook]

When it comes to new outlets I always go big it lessons the voltage drop and if your already spending the cash your prepared for bigger better things in the future in my shop I have three 220 outlets all running # 8 on 50 amp breakers since your only going a few feet it won't cost much more to "over build it"

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[cj737]

10AWG Copper, 2 wire is all you need. Skip the aluminum wire. 10 is over rated, but if you ever need to bump the fuse, then you’re ahead of the game to handle up to 50 amps at that length.

[LanceR]

I'm also a fan of over-sizing conductors in a garage or shop to allow for future changes at minimal expense and delay, especially on this short of a run. But I have some concerns with a few of the answers given so far.

I don't think that the claims that 12 AWG copper can carry 25 amps or that 10 AWG copper can carry 50 amps are accurate in a circuit . Then question is not what the potential ampacity of the wire is but what overcurrent protection is allowed. The National Electric Code "small-conductor rule" often limits 14 to 10 AWG copper, aluminum and copper clad aluminum circuits to lower overcurrent protection ampacities than the potential ampacity of the wire itself.

A circuit sizing quote worth reading...."It is important to keep the small-conductor rule in mind when sizing 14, 12 and 10 AWG conductors because the maximum rating for the overcurrent device may be less than the maximum ampacity of the conductor."

The following footnote is extracted from a current NEC derived table discussing the allowable ampacities of wire:

"Unless specifically permitted in Section 240.4(E) through (G), the overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for 12 AWG and 25 amperes for 10 AWG aluminum after any correction factors for ambient temperature and number of conductors have been applied."

And I don't think the rule allowing a dedicated circuit for a welder to be undersized applies as the OP is discussing a plasma cutter which is not, I believe, included in the NEC welder exception. And I'm neither an electrician nor a weldor so I only ever saw one case where the use of undersized conductors in a welder circuit rule was invoked. The electrical inspector required that all welders on those circuits be hard wired and that there be no plug receptacles to prevent any device not allowed to operate on undersized conductors being plugged in....

And, in any case, the NEC tables I'm looking at would seem to limit THHN and similar 10 AWG copper to a maximum of 40 amps under any conditions anyway.

If anyone has a source that shows something different please post back.


Thanks,


Lance