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Thread: 220 V wiring question

  1. #1
    Join Date
    Jan 2012
    Bumpass, VA

    220 V wiring question

    The new shop is coming along nicely and now I'm starting to rough in the wiring and I have a question.

    Has anybody ever put 2 - 220v outlets on the same circuit? My table saw and Joiner sit next to each other. The table saw runs on 220. The joiner originally ran on 110, but in my old shop I had a concrete floor and was too much trouble to run a new 110 line and I didn't want cords running across the floor, so I converted it to 220 and just plugged and unplugged each one as needed. That turned out to be a pain. So I thought about putting a second 220 outlet in so I could leave the joiner plugged in. So I was wondering if I could just tap off the circuit for the table saw. The circuit is 20amp and even though it could handle both tools at the same time, I don't see myself running them at the same time, and I really don't want to take up breaker space for another 220v circuit. I only have 20 spots as it is. I've checked with a couple of residential electricians, and they say it's possible electrically to do, but they have never had a reason to. We've looked through the code and it doesn't really address it. It does address certain appliances/functions need to be on a dedicated breaker, but not if you can put two outlets on a 220 breaker.

    So this boils down to four options
    1. Keep things as they are and plug and unplug
    2. Run 2 - 220v circuits, 1 for each tool
    3. Convert the Joiner back to 110 and run a 110 outlet for it. (I am planning on 2 - 110 retractable cord reels from the ceiling, one near the table saw area to power the lunch box planer that sits on the out feed table and one near the workbench, and could possibly use it for the joiner, but still would need to unplug it when not in use.)
    4. run a second outlet off the table saw circuit.

    Any ideas?

  2. #2
    Join Date
    Nov 2006
    Delton, Michigan
    how large is the jointer? if its a 6" then i would go back to 110 and be safe,, if its a 8" then the idea of 220 for it is good because it has larger motor.. but i cant say it ok to put 2 220 receipts in one circuit the sparkys need to answer that.. just for grins ask google the question and see what you find out there..
    If in Doubt, Build it Stout!
    One hand washes the other!
    Don't put off today till tomorrow!

  3. #3
    Join Date
    Jan 2007
    Sacramento, CA
    You can definitely put multiple 220v outlets on a 20a circuit. I'm not sure the rules are the same for 30 or higher, though.
    Jason Beam
    Sacramento, CA

  4. #4
    Join Date
    Jul 2011
    The Gorge Area, Oregon
    Its fine from an electrical perspective. Some places don't allow it because of rules around dedicated circuits and worries overloading them so it may or may not be strictly to code depending on local rules (there is definitely code around this of you look hard enough).

    I would put the split in a junction box before the existing outlet so you have plenty of space to work in (and leaving enough space in the box keeps it from overheating the wire as well).

    When you go to sell the place just pull the last outlet off of the circuit and patch the holes so as not to confuse the inspector.

  5. #5
    Join Date
    Nov 2012
    Wapakoneta, OH
    It's perfectly acceptable to put 2 outlets on one line with 240V. With one exception, every 240V circuit in my shop (there's 6) has more than one outlet. 2 of those circuits are 30 amp. The one exception is the one the DC runs on, it's dedicated. But a 240V duplex might be easier...I put in a few of those as well.
    Last edited by fred hargis; 09-18-2014 at 09:39 PM.

  6. #6
    Join Date
    Oct 2006
    ABQ NM
    When I had the subpanel added to my shop, the electrician told me that the local code disallowed dual 240v outlets on the same circuit. I worked around this by installing single wall and ceiling 240v outlets, then building 10' 240v extension cords with a junction box and two outlets at the end. With only one exception, I'm never running two 240v tools at the same time on the same circuit, but I wanted the convenience of not having to switch plugs all the time. (That one exception is when I run my lathe and vacuum pump at the same time. They are on a 20 amp circuit. The vacuum pump pulls something like 1/4 of an amp at 240v, and the lathe pulls fewer than 7 amps.)
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

  7. #7
    Code generally only puts restriction of fixed in place loads.

    Also, the question of converting back to 120v, being a garage or a detached building at grade level would require the 120volt receptacle to be ground fault protected GFCI. NEC 210.8(A)(2).

    Under the multioutlet Branch circuit section of the code it simply requires the conductors be protected at there listed ampacity (#12 conductors protected by 20Amp circuit breaker, #10 conductors protected by 30amp circuit breaker.) NEC 210.19 (A)(2).

    Where you have multiple outlets on a branch circuit, TABLE 210.21(B)(2) shows the maximum load any single outlet can carry ( for 20amp receptacle = 16amps, for 30amp receptacle=24amps.)

    The receptacle rating for branch circuits with multiple outlets need to be: for a 20amp circuit breaker =15amp/20amp receptacle; for a 30amp circuit breaker= 30amp receptacle. NEC TABLE 210.21(B)(3).

    For 15amp and 20amp loads for cord and plug not fastened in place equipment the load connect exceed 80% of the branch circuit rating. NEC 210.23(A)(1)

    Permissible loads on a 30amp branch circuit: NEC 210.23 specifically refers to two or more outlet/receptacles (thus allowing multiple 30amp receptacles on a single branch circuit) but NEC 210.23(B) adds that any single cord and plug load cannot exceed 80 percent of the branch circuit rating.

    So yes you can put multiple 20amp receptacles on a 20amp circuit breaker and multiple 30amp receptacles on a 30amp circuit breaker.


  8. #8
    Join Date
    Jun 2007
    Oceanside, So. Calif. 5 mi. to the ocean
    Each of my 220v machines is on a dedicated breaker. However, I did this only because I had an electric box that would handle it. I just tossed this in as a "what I did," not as a what is necessary.

    First of all you have to be smarter than the machine.

  9. #9
    In my case I am a "one man" shop and I do have a lot of big power tools and my original intent was to feed each with a separate branch circuit. I was going to add a sub-panel off the main to handle everything.
    To cover every tool would require:
    Seven 30A/2P
    Four 20A/2P
    Five 15A/2P
    Four 20A/1P
    One cyclone 30A/2P
    One Air Compressor 50A/2P
    to supplement the general purpose outlets.

    Because I have never been satisfied with the tool location/layout, I was always moving them around, so to put in fixed outlets just was not feasible yet. So as in interim, I have a temporary sub-panel beside the main panel that has an assortment of twist-lock receptacle configurations and have a number of heavy-duty extension cords with twist-lock receptacles on both ends that can reach any tool in the shop.

    Now that I at 90% sure where everything is going to live somewhat permanently, I was laying out dedicated receptacles for every tool. The more I thought about it though I realized that I am too anal about up-plugging tools when they are not being used. So why was I trying to have dedicated receptacles for each.

    The current plan is to have a group of 4-5 tools to feed from a few common circuits and just replace the SWOOJ cords on the tools to reach the receptacles.

    So for example one group of tools : Dual drum sander, Planer, Shaper (all 5 horsepower) that all require 30A/2P circuits, small Jointer (2hp) requires a 20A/2P and the power feed for the shaper requires a 20A/1P. So they will get just three circuits.

    Another group: Big Jointer, Big Bandsaw, Radial Arm saw (all 5 horsepower) will require a 30A/2P, Tablesaw (3hp) will get a 20A/2P. So they will get just two circuits. In this case I am even thinking about bringing over just a single 30A/2P circuit and tap it with a separate fused disconnect at 20amps to feed the 20A/2p to feed the Tablesaw, so that I will just need one actually branch circuit dropped from the ceiling above.


  10. #10
    Join Date
    Jan 2012
    Bumpass, VA
    Thanks for the suggesting. I think for now I'm going to follow Rob's lead and not put in the 220 circuits just yet. I have easy access underneath from the crawl space, so I'm going to to wait for a few months to make sure the tools are where I want them and then run the circuits. I'm planning on doing the same thing with the dust collection too. Using my portable collector for now till all the stuff is finally situated.

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