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Thread: what size wire for my 220v outlets?

  1. #1

    Question what size wire for my 220v outlets?

    I need some help on ? size wire to run
    I already have 12-2 wire for the 120v runs
    what amps do most 220v shop tools use
    some of the tools that Im thinking of geting in the future(220v)Grizzly cabinet saw I think it pulls 18amps and a larger DC 15 amps and a AC ? on the amps.
    Jim

  2. #2
    Quote Originally Posted by Jim Ketron
    I need some help on ? size wire to run
    I already have 12-2 wire for the 120v runs
    what amps do most 220v shop tools use
    some of the tools that Im thinking of geting in the future(220v)Grizzly cabinet saw I think it pulls 18amps and a larger DC 15 amps and a AC ? on the amps.
    Jim
    Jim,

    Most 220V tools require a 30 Amp circuit. That means you'll need to run a 10-2 w/grnd to the outlet. 10-2 copper wire is normally good for up to 40 Amps on start loads and will sustain 35 Amps on constant load. All my tools that are 220V run easily on 10 guage wire. I even have my cyclone on 10 guage wire and it peaks at 42 Amps under start loads with no problems here.

    Just in case you need to know:
    12-2 w/grnd is good for up to 20 Amps.
    14-2 w/grnd is good for up to 15 Amps.
    10-2 w/grnd is good for 30 to 35 Amps.
    #8 Aluminum is good for 40 Amps.
    #6 Aluminum is good for 50 Amps.
    #4 Aluminum is good for up to 70 Amps.
    1 Aught Service Cable is good for 100 Amp service
    4 Aught Service Cable is good for 200 Amp service.

    Extension cords are good for almost everything!!!
    Thanks & Happy Wood Chips,
    Dennis -
    Get the Benefits of Being an SMC Contributor..!
    ....DEBT is nothing more than yesterday's spending taken from tomorrow's income.

  3. #3
    Quote Originally Posted by Jim Ketron
    I need some help on ? size wire to run
    I already have 12-2 wire for the 120v runs
    what amps do most 220v shop tools use
    some of the tools that Im thinking of geting in the future(220v)Grizzly cabinet saw I think it pulls 18amps and a larger DC 15 amps and a AC ? on the amps.
    Jim
    20A 220v circuits will handle most 3hp or less motors, 30A will handle most 5hp motors. Wire sizes (excluding derating for various reasons) would be 12ga and 10ga respectively. Besides wire sizes you will need to be aware of box fill and most likely conduit fill restrictions. I suggest that you get a copy of the NEC and read up on branch circuit wiring.

  4. #4
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    I used a minimum of 12 - 3 w/g for my 220 volt outlets. I ran 8 or 10* - 3 w/g for the 5 HP compressor ckt. and spotted in 4 more 40 Amp 220 boxes for other 5 HP equipment (now that is real 5 HP motors the 28 Amp @ 220V kind). Welder outlets are wired with 6 - 3 w/g.

    Black and Red wires carry your 120V each, White the netural (or return of any unbalance) and the ground(bare wire) is available as an equipment ground.

    I have been watching your shop come together and enjoying the updates with photos, looks great!

    *I had posted 10 gage originally but now I think maybe it was 8 - I will check it out tomorrow. It's late and my memory has gone south.
    Last edited by Steve Stube; 08-17-2004 at 2:31 AM.

  5. #5
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    Quote Originally Posted by Dennis Peacock
    Jim,

    Most 220V tools require a 30 Amp circuit. That means you'll need to run a 10-2 w/grnd to the outlet. 10-2 copper wire is normally good for up to 40 Amps on start loads and will sustain 35 Amps on constant load. All my tools that are 220V run easily on 10 guage wire. I even have my cyclone on 10 guage wire and it peaks at 42 Amps under start loads with no problems here.

    Just in case you need to know:
    10-2 w/grnd is good for 30 to 35 Amps.
    Dennis,

    FYI, #10 is limited by the NEC to a 30 amp breaker. A breaker will carry around 10x rated current for startup loads, unless it's a "long" start in which case you need a HVAC-rated breaker.

    Jim,

    If you're planning on running #10, do yourself a favor and use the largest boxes you can. I don't know if you're planning to sheetrock, but the 4 11/16 x 4 11/16 2 1/8 seems cavernous until you're trying to stuff a bunch of stiff wire into it. Give yourself the extra room.

    If you're running conduit, you need to pull individual conductors. With conduit, you also need to worry about derating because of an ampacity adjustment factor ifyou have more than 3 current-carrying conductors (CCC's) in a raceway (conduit). Put simply, that means if you have (2) 240v, 30-amp circuits pulled through the same conduit - that's 4 CCC's which means an adjustment factor of 80% from table 310.15(B(2)(a). That means, to get a 30 amp circuit, you'd need to pull #8. Conduit is nice for expansion, but it can get tricky.

    Rob

  6. #6
    [QUOTE=Steve Stube]I used a minimum of 12 - 3 w/g for my 220 volt outlets. I ran 8 or 10* - 3 w/g for the 5 HP compressor ckt. and spotted in 4 more 40 Amp 220 boxes for other 5 HP equipment (now that is real 5 HP motors the 28 Amp @ 220V kind). Welder outlets are wired with 6 - 3 w/g.

    Black and Red wires carry your 120V each, White the netural (or return of any unbalance) and the ground(bare wire) is available as an equipment ground.

    Now I'm confused. I understand the 20amp/30amp break, but not the 10/2 - 10/3 break. I assume that's for 1-phase vs. 3-phase motors. When will the average home shop need the 10/3 (3-phase) service? I also don't understand why Dennis went from copper to aluminum. I was planning on 6ga copper for my 60 amp service (80 ft from the house panel to the separate garage).

    Bob
    Spinning is good on a lathe, not good in a Miata.

  7. #7
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    Bob, the copper vs aluminum decision is often made for cost reasons on thick service cables...aluminum is less espensive but is also physically larger. Some special care is also required when terminating it relative to corosion prevention. Also, the "10/3" designation has nothing to do with 3-phase. It's just an indication that the cable has three conductors plus a ground...usually...the exception being "cord" material off the roll at the home center where it has two conductors plus ground. If you buy "Romex" cable designated as 10/2 (or 14/2 or 12/2), it will have two conductors plus a ground. X/3 "Romex" will have three conductors plus a ground. Most 240v equipment we use in our shops only requires two conductors plus ground. A third conductor (typically used as the "neutral"), if available, isn't used for those devices but would be necessary for a dual voltage situation where something on the device requires 120v, such as a clock, timer or light. Please note that some localities require that x/3 cable be pulled, even if the third conductor is not needed for the application.

    Jim K...I'd suggest you pull 10 guage cable for your 240 volt circuits just to cover yourself for future tool purchases. The cost difference is negligable! While most things run fine on 20amp, it really depends on the tool. My MM16 is using a 20amp circuit as is my TS and Lathe. But the "aircraft carrier"-like FS-350, with it's 4.8hp motor requires a 30amp feed. With 10 guage wire, you can easily upgrade (or downgrade) the circuit to or from 30amp by changing the breaker, outlet and plug(s) at any time...that beats pulling new wire any day!
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  8. #8
    Quote Originally Posted by Bob Hovde
    I also don't understand why Dennis went from copper to aluminum. I was planning on 6ga copper for my 60 amp service (80 ft from the house panel to the separate garage).

    Bob
    Bob,

    I'm an Ex-electrician. We always ran the "big wire" in aluminum due to the cost. So I quoted you what I ran in 500+ houses. Stove, dryer, HVAC unit and all got aluminum wire. The rule we used was provided by our inspector: If you use Aluminum wire, you must go one size larger in wire guage. I personally would run everything in copper, as what I did in my own shop. I didn't like aluminum wire then and I don't like it today.

    Check the service cable on your house going to your panel and the wire going from your meter-base to the pole (commercial power source). You will find "aluminum wire".
    Thanks & Happy Wood Chips,
    Dennis -
    Get the Benefits of Being an SMC Contributor..!
    ....DEBT is nothing more than yesterday's spending taken from tomorrow's income.

  9. #9
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    Quote Originally Posted by Dennis Peacock

    ... Stove, dryer, HVAC unit and all got aluminum wire. The rule we used was provided by our inspector: If you use Aluminum wire, you must go one size larger in wire guage. I personally would run everything in copper, as what I did in my own shop. I didn't like aluminum wire then and I don't like it today. ...
    Cheaper is right, especially with copper prices cranking up recently. There are a number of cases now where you need to go up 2 gauges to get the matching ampacity out of aluminum that you do copper (ex. 100 amps @ 75 degrees [typical residential breaker terminal temp rating] = #3 copper but #1 aluminum).

    The other problem with aluminum is oxidation. A lot of DIY'ers don't use antioxidant on the exposed aluminum so you can get corrosion over time at your connection points (and that's a bad thing). All the big box stores carry OxGard or a similar antioxidant. It comes in a little tube that you spread on/work into the exposed aluminum (I used a glue brush on the OxGard when I ran aluminum SER for my subpanels).

  10. #10
    Thanks Jim and Dennis,

    It's starting to come back, now . . . I think 10/2 in my (separate) garage is fine - no appliances there.

    Bob
    Spinning is good on a lathe, not good in a Miata.

  11. #11
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    Quote Originally Posted by Dennis Peacock
    Bob, ....

    Check the service cable on your house going to your panel and the wire going from your meter-base to the pole (commercial power source). You will find "aluminum wire".
    Dennis, it is my understanding that aluminum wire is used up to your meter because electric utility companies are not required to abide by the NEC, and/or local regulations, rather by what the federal govt. allows.

    I was told by a Texas licensed electrician that the only city in Texas that permits the use of aluminum wire in residential construction is San Antonio. Copper is clearly better for house wiring, and I don't believe the cost savings is worth the potential fire risk due to a bad junction.

    That is my story, and I am sticking by it.
    Best Regards, Ken

  12. #12
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    Jim,

    I'm putting #10 EVERYWHERE in my garage remodel. A 500' spool at HD is $50 and I have black, white, red, and green. These are all stranded, not solid core, too.

    I'm also running everything through 3/4" flex conduit (so far!) and plan to keep only 4 wires per conduit if I can help it so I don't get nailed too hard by the deregulation that Rob points to above. 4 #10s pull nicely through the 3/4" flex.

    I'm also running #10 everywhere because I didn't want to purchase rolls of #12 or #14...too much money and too many rolls to deal with.

    Yes, I'm discovering that the flex is a pain and while it flexes...it doesn't flex as much as I would have liked it to in certain situations (I'll update my "Padilla's Garge Gut/Remodel thread soon). It is also kinda painful to cut but I'm getting the hang of it.

    I'm mainly putting flex in for future upgrade (or downgrade) ease in my shop. I plan to run a few empty conduits here and there with some empty junction boxes here and there, too.

    All my boxes are the large 4 11/16" x 4 11/16" x 2 1/8" and all will get 5/8" mud rings.

    I plan to multi-wire each 120 V box (2 duplex plugs, each on a different circuit but on the same breaker so 1 duplex plug will get a black hot and the other will get a red hot). Keep in mind you only need 1 white (nuetral) for this wiring scheme and of course, the green ground.

    If you plan to use the 240 V twist-locks, I highly suggest you mount the boxes very, very well. Those plugs put some strain on the outlet due to weight just hanging there as well as effort to plug in and out.
    Crown Molding: cut, cope, cuss, caulk, chill....

    Did you know SMC is user supported? Please help.

  13. #13
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    Quote Originally Posted by Chris Padilla

    ... so I don't get nailed too hard by the deregulation that Rob points to above ...
    Umm - derating ??? Note that it's 4 or more current-carrying conductors. The grounding conductor doesn't count.

    I agree with the rest of your post. A quick tip. When working with stranded wire, twist it counter-clockwise before forming a loop to go around your terminal screws. It'll stay tighter.

    Rob

  14. #14
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    Okay, deRATING! I knew there was something funny about that when I typed it out!

    Thanks for the tip on the derating and green wire...I should be in good shape then.

    I planned to get those outlets that are back-wired (I think that is the correct term) and you just insert the wire and clamp down on it...no loops to make. Very, very nice.
    Crown Molding: cut, cope, cuss, caulk, chill....

    Did you know SMC is user supported? Please help.

  15. #15
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    Quote Originally Posted by Chris Padilla

    I planned to get those outlets that are back-wired (I think that is the correct term) and you just insert the wire and clamp down on it...no loops to make.
    If you're talking about the true back-wired receptacles, where the side terminal screw is part of the clamping mechanism and tightening the side screw also tightens the clamp on the back-wire - that's fine.

    If it's a back-stab receptacle where you push the wire into a hole and a spring plate holds the wire in - you don't want to use those. The spring plates can loosen up over time, the connections heat up and cause fires.

    I suspect you're talking about the true back-wired devices, for example the Leviton commercial or industrial specification grade ones. Those are rated for #10 solid or stranded conductors in the back-wire holes. You do need to make sure the receptacles you buy are rated for #10 stranded, because that's what you're using. I don't know if all back-wire receptacles are rated by the manufacturer for #10 stranded. Probably are, but it's worth checking.

    Rob

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