220v/20A extension with L6-20 plugs

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Topic by MrMeasureTwice posted 08-22-2012 02:49 AM 19045 views 0 times favorited 11 replies Add to Favorites Watch
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12 posts in 2280 days

08-22-2012 02:49 AM

Topic tags/keywords: question garage electrical parts

Hi Folks,
I am usually over on LumberJocks mostly, but now I have this awesome table saw that runs on 220, single phase. It has an L6-20 plug on it, so I am making an extension, but not sure about whether wire colors matter for the black and white wires – green I know IT MATTERS.

There are three blades on the male plug. G, X and Y. G is ground and the green wire goes there. But both the white and black are HOT. What I am trying to decide is whether it matters whether white goes to X or Y?

Is there a standard somewhere? I cannot seem to find it easily, and, I am a damn good “Googler”...

If someone KNOWS the answer, not an opinion, but KNOWS, then please let me know.

Remember, we’re talking 220v here – not exactly what I want to be fooling with on an opinion, or “I think it’s…” type of answer.

Jim ””Mr. Measure Twice””:http://www.mrmeasuretwice.com/ Marchetti

-- -- Jim “Mr. Measure Twice” Marchetti -- http://www.mrmeasuretwice.com/

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70 posts in 2318 days

08-22-2012 05:58 AM

Yes, both X and Y are hot. An L6-20 plug is a 3 prong twist lock plug that has one ground and two hot connections, there is no neutral in the plug, so no neutral (usually white goes back to the bus bar). If you are putting in a new breaker in your panel and using Romex with bare/green, Black and White—then the hot white should be marked at both ends with black electrical tape (unless your local code says otherwise, but NEC likes black tape in a home wiring environment. An industrial environment may require slightly different color markings) to denote that it is also a hot leg.

X and Y—they are both 120v hot legs, so it doesn’t matter what color wire (as long as it isn’t a bare wire) you connect to either terminal as long as you put some black tape on the breaker end and the plug end of the wire to denote it (usually white) is hot instead of neutral, then you should be in compliance with the NEC (as long as you havent gone and done some “creative” wiring by changing loads or tying your new hots into an existing breaker, or adding the load on to some existing properly loaded circuit, thus changing the load to an unsafe one).

-- I found the board stretcher... finally!

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12 posts in 2280 days

08-22-2012 06:14 AM

@J – thanks so much. I was pretty sure about it, as you described, but wanted to be sure and figured there’d be someone on here to confirm.

I have room on my panel for two 220 breakers and will put outlets in my woodshop portion of the 3 car garage. I have two tools that use 220, a table saw and a bandsaw. Each only draws 9-12 amps, so well under the 20 amp breakers I plan to put in for these two items.

I’ve used L6-20’s in the past in data centers, but never had to wire them, so that is where my question came from, and, the table saw has an L6-20 on it already, so sticking with that as my “standard.

Now I know what next weekend looks like for me – YAY!!!

Thanks again J for the guidance.

—Jim Mr. Measure Twice Marchetti

-- -- Jim “Mr. Measure Twice” Marchetti -- http://www.mrmeasuretwice.com/

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Dan Lyke

331 posts in 3881 days

08-24-2012 03:40 AM

J, any reason to not run 10/3 and just put a cap on the neutral in the box? I’m an “anything worth doing is worth doing to excess” kind of guy, but when I wired my shop I did that for the 220 circuits, figuring that at worst I just wasted a few feet of extra conductor: no biggie.

-- Dan Lyke, Petaluma California, http://www.flutterby.net/

View J's profile


70 posts in 2318 days

08-24-2012 04:12 AM

I generally run my shop wiring in conduit so I can pull it out and upgrade as needed. In my case individual sheathed wires are just fine because I am familiar with the NEC and my local codes.

I would recommend xx/3 (10/3 in your case) if you think there is any chance you might change up your equipment, but for 12 amps you could save some money by using 12 ga wire.

If you do install 10/3 then there are not too many tools that you would have have to change your wiring to accommodate, it then becomes a matter of what your plugs are rated to handle.

The only issue becomes if you choose to install a shop tool that would operate on 3 phase power.

10/3 romex (with bare ground) will cover nearly any expansion you could make to a home shop. The wire is cheap, it is the plugs and receptacles that really add cost to a project.

I am willing to bet you know this, but if not:
14 ga wire is rated to 15 A max
12 ga wire is rated to 20 A max
10 ga wire is rated to 30 A max

A safe circuit is loaded at 80% of max Amps

-- I found the board stretcher... finally!

View MrMeasureTwice's profile


12 posts in 2280 days

08-24-2012 04:17 AM

@Dan – with the price of copper these days, I went with 12/3, and, since none of my tools will be over 20A, I think I am fine…

Of course, that could change… who knows, I may go “Tim Tayolr” and need MORE POWER! :-)

-- -- Jim “Mr. Measure Twice” Marchetti -- http://www.mrmeasuretwice.com/

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