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Thread: 220 volt 20 amp circuit question

  1. #1
    Join Date
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    220 volt 20 amp circuit question

    I think I know the answer but wanted to run this by the group for verification.
    I just ordered the Grizzly G0514x2 Bandsaw and in the specs it requires a 220 volt 20 amp circuit. This is my only 220 volt tool besides my Air Compressor which I have installed about 2 years ago. It required a 30 amp circuit, I wired it with 10 gauge wire. Anyway back to my question, as far as I can tell 220 volt 20 amp requires 12 gauge wire. I already have a bunch of 12-2 with ground romex left over from wiring the 110 outlets in my shop. Will this wire be sufficent for the 220 volt 20 amp circuit? I figure 20 amps is 20 amps. Just use the Black and White for each 120 leg and the bare ground for the ground. Does this sound correct?

    Thanks Mike

  2. #2
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    You are correct Mike, just tape the white wire with red tape to indicate that is no longer a neutral wire.

    Enjoy your new saw.......Rod.

  3. #3
    20 amps is 20 amps, put a piece of red tape on the white wire on each end to signify it's use as a hot leg.

  4. #4
    You can do that but at least buy some red tape or black to wrap all of the exposed insulation on the white wire just so there is no confusion. The better option would be to buy some 10ga wire and run it and then you have the option of just changing out the plug and breaker later if you need to upgrade to 30.

    Hmm three replies at once :O

  5. #5
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    Thanks for the quick replies. Now all I need is a breaker, receptacle and a plug.

    Appreciate the feedback
    Mike

  6. #6
    The 20A breakers are nice because they take less room in your breaker box. If you want 30A you will need a double. It's a bummer because I often wish I had just installed 30A wire+breakers on all my 220V circuits instead of 20A. Each of my 3HP Grizzly machines and my 3HP Oneida cyclone has tripped a breaker on startup at least once over the years. With 30A though my breaker box would have run out of room fast.
    -Brian

  7. #7
    Maybe I missed something here, but I think someone is waaaaayy off base: The OP asked about wiring a 220V circuit with 12-2 w/ground Romex. Not only NO, but H!!! No! (In the USA) Any 220V circuit requires an xx-3 w/ground wire, xx depending on the ampacity. For 220V you have to have 2 hot leads and a neutral. (In Europe, base voltage IS 220, so an xx-2 CAN carry 220) You can't (if you want to follow codes, that is) use an un-insulated ground lead as a neutral. So your 12-2 w/g is good for 20 amps of 110V, and for 20 amps of 220V you need 12-3 w/g.

    And as for the 20 vs 30 amp breaker size, HUH? The physical size of the breaker depends 1) on whether you full height or 1/2 height breakers, and 2) whether you have single pole (110V) or double pole (220v) breakers. Boxes are designed to take full height breakers. Using 1/2 height breakers allows you to place 2 circuits in place of one, as long as you don't exceed the box design limits. IF your box is designed to supply 220V circuits (and most are), then adjacent slots are desgined to feed from alternate lines (hot line 1 then hot line 2). For a 220V circuit, a double pole breaker is used, and if full height, straddles 2 adjacent; if it's a 1/2 height, it straddles (for example) slot 4B and 6A, which are adjacent, on the right side of the box.

    All of this info is pretty basic, and if not aware of it, I would recommend hiring a licensed electrician.

  8. #8
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    Quote Originally Posted by Dick Thomas View Post
    Maybe I missed something here, but I think someone is waaaaayy off base: The OP asked about wiring a 220V circuit with 12-2 w/ground Romex. Not only NO, but H!!! No! (In the USA) Any 220V circuit requires an xx-3 w/ground wire, xx depending on the ampacity. For 220V you have to have 2 hot leads and a neutral. .
    Dick, that's not correct, a device that is only 2 pole only requires 2 conductors, plus ground, no neutral required.........Regards, Rod

  9. #9
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    That was my assumption as well, since my Air Compresser and Welder only has has 2 pole 220 with a ground. Heck my house is only 3 wire from the utility pole. With the ground and neutral bonded in the panel. I guess my real concern was with the ground being uninsulated.

    Mike

  10. #10
    Join Date
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    Washington, NC
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    Two hots and a gnd. 12-2 w/gnd ROMEX.

  11. #11
    Dick if you have an above ground service entrance take a look at it, there are two hots and a ground coming from the utility, if you run a neutral and a ground up to the weatherhead the power company will tie them together. In 110 the neutral is also a current carrying conductor but one that will not normally carry current all the time. Now 12/3 or 10/3 etc is used on quite a few things like driers etc that also need a neutral, normally 230(220) motors do not need a neutral so wiring with two current carrying conductors will work. The easiest way to think of it is that the appliances that need a neutral usually have electronics that require 115. If you wire a machine to use a 6-20 plug your only option is to cap the neutral or bond it to the ground, depending on your service panel.

    Just to clarify further on your main service panel the NEC does not require ground and neutral to be seperated though most seperate, there is even a bonding bar included to connect the two bars. Now if you have a disconnect it is treated like a subpanel where they must be seperated. I brought this up to make you think about the role of the neutral wire and that it is used as a way to regulate the current on 115/110 circuits.

    As for the breaker size, you are exactly right. Single pole and double pole breakers are the same size no matter the amp rating.
    Last edited by Al Burton; 04-20-2011 at 10:06 PM.

  12. #12
    Rod/Al: Mea Culpa! Engage brain before opening mouth! I guess I got scrambled & was thinking of driers, ranges, etc - of course they all use both 220 & 110 (controls, lights) and need the neutral. I don't have anything in the (in-progress) shop wired for 220, and pre-retirement, all 220 & higher equipment was 3-phase, Y!

    Thanx for correcting me!

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