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Thread: 220 V Outlet Configuration / Sawstop Question

  1. #1

    Question 220 V Outlet Configuration / Sawstop Question

    My family an I are patiently waiting for the completion of our home - construction is due to finish the end of this month. One of the garage spaces is called an "RV" spot, and I see that the builder has included a 220 volt outlet, presumably for some sort of RV hookup. We have no RV but my eye is on this large space is not for parking, but for my new workshop - wahoo!

    Anyway, I had sold my old Craftsman contractor saw when we left California and the wife said I can buy a new table saw (wahoo #2!). My wish/plan is the 3 HP, 220 volt Sawstop PCS. Looking at the Sawstop web site, it appears that the saw will come with a NEMA 6-15P plug (round ground prong and two flat horizontal hot / neutral? prongs). Well, the outlet the builder has installed has FOUR holes in it: one round ground plug at the bottom, two flat 45 degree holes on the sides, and one flat horizontal hole at the top).

    Worst (best?) case would be to have an electrician re-do it but if this is something simple that I can change out I'd sooner do it myself. However, I don't want the new saw to turn into a large flaming mass, either.

    I am not familiar with 220 volt plugs or receptacles - can anyone here venture an educated guess as to what the heck sort of outlet this is? I know that the Sawstop manual describes how to replace the supplied cable with one of your choice, but what the heck is that fourth hole for on the outlet?

    Thanks, Jim

  2. #2
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    The 4 terminals are: hot, hot, neutral, ground. I'm not familiar with RV's, but they must use the neutral to pull 120V/240V power at different places. Your Sawstop has two hots and a ground; no neutral...all the electronics run on 240V.

    Switching the receptacle over is trivial - just buy the correct one the Sawstop uses, shut off the breaker (AND TEST IT), open the box, and re-wire it - capping the now unused neutral. You must validate the breaker and wiring are sufficient for the amperage you'd be pulling - validate the breaker is rated at whatever Sawstop recommends, AND the wiring must be rated to support that amperage (i.e. 20 amps or 30 amps).

  3. #3
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    Alternatively, if that plug is wired with sufficiently sized wire, perhaps you could have the builder put in a subpanel instead of a huge RV outlet (could be 50 amps, could be 30 amps). Two hots, and a separated neutral and ground would work very nicely for that - then you can put in an array of outlets for your shop.

  4. #4
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    Excellent advice. I would just add that you might want to check the amperage on the existing RV circuit. If, for example, it is a 50A, then that location would make a nice small breaker box from which several 240V/20A circuits and/or 120V circuits might be run. It would turn it into an electrician project instead of simply swapping the outlet, but if your shop plans include more than just the one 240V tool, it may be worth doing it.

  5. #5
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    Exactly, without a photo or some specs, it is hard to know what RV outlet you're staring at. A 50 amp circuit would be a wonderful opportunity. Have the builder do this if possible while everything is still rough, it'll be a game changer for your intended shop.

    Quote Originally Posted by Dave Mills View Post
    Excellent advice. I would just add that you might want to check the amperage on the existing RV circuit. If, for example, it is a 50A, then that location would make a nice small breaker box from which several 240V/20A circuits and/or 120V circuits might be run. It would turn it into an electrician project instead of simply swapping the outlet, but if your shop plans include more than just the one 240V tool, it may be worth doing it.

  6. #6
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    Worst (best?) case would be to have an electrician re-do it but if this is something simple that I can change out I'd sooner do it myself.
    FWIW - I'd get an electrician out - or - talk to the electrician that did the wiring in your house - and discuss your plans for putting in a shop.

    In addition to the one 220V outlet for the saw, you're going to want several 120V GFI outlets - maybe A/C & heat, lights and dust collection.
    Plus - that gives you enough to add a 220V plug for an electric vehicle if you have to get one of those things.

    I plan to have the electrician put in a 60 amp subpanel in the third bay garage of our new place that's being built.
    Last edited by Rich Engelhardt; 06-08-2021 at 1:30 PM.
    My granddad always said, :As one door closes, another opens".
    Wonderful man, terrible cabinet maker...

  7. #7
    Guys - thanks for the replies! I neglected to mention that I also would be using the outlet for nightly charging of my hybrid SUV. I can schedule that for the wee hours of the morning. But, after reading the replies, I think my best bet is to bite the bullet and have an electrician come out to assess the amperage capacity of that line and if possible, add one or two other 220 outlets for my woodworking equipment.

    Thanks again, Jim

  8. #8
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    remember if it is say a 30 amp outlet you can run a 100 amp panel off of it. Thiis gives you lots of extra space for latter expansions. Rule of thumb is any panel should have at least two empty slots for latter additions. So if you need 6 slots now get at least eight in the new panel. A 240 circuit uses two slots, a surge protector uses two more slots. So it adds up fast. I see saw, ac, welder, planer, car. so right there it is 10 circuits plus 120 stuff. Keep lights on there own breakers not on the general use 120 outlets.
    Is is convenient to use the same make of breaker as existing in the house so you can swap stuff around for testing etc. Or if something fails sunday night you can pull and replace the more critical use for a day. Just not Zinsco or federal pacific. I like square D QO breakers. still being sold 50 years latter. Lots of cheap used ones for sale.
    Bill D
    Last edited by Bill Dufour; 06-08-2021 at 2:32 PM.

  9. #9
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    Just put a 240v 4-wire plug that matches your receptacle on the saw. The neutral will not get used... This preserves the outlet "as it" for other applications such as your EV charging. You can, of course, make a pigtail to "adapt" the saw's "native" plug, but that costs more money than just changing the plug.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #10
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    I agree with Jim. My table saw is jumpered to 220. It does not bog down. You will wire the wall plug with proper outlets which if I remember correctly, can be purchased at Lowes or Home Depot.
    If you are nervous doing it, hire an electrician.

  11. #11
    You want the breaker sized to your saw, you want it to trip in a fault condition not hit the saw with 50+ amps before it trips. I say run a 2nd 220v outlet for the saw and a 3rd 220v for a dust collector each sized appropriately. I have a 5hp ICS and 3hp cyclone, went with 30 amp twist lock plugs and outlets for both.

  12. #12
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    Quote Originally Posted by Bill Dufour View Post
    remember if it is say a 30 amp outlet you can run a 100 amp panel off of it.
    I don't think this is true, though I'd second getting an electrician out. It's all going to depend on the gauge of wire at that outlet. A 100 amp panel would require (at least) 3AWG copper. A 30A outlet likely only has 8 or 10AWG.

    I'd echo the idea of having a 50A sub-panel put in in place of the existing outlet, then wiring some combination of new 220 and 120 circuits based on the equipment you have.
    Last edited by Patrick Varley; 06-08-2021 at 8:39 PM.

  13. #13
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    Quote Originally Posted by Charles Coolidge View Post
    You want the breaker sized to your saw, you want it to trip in a fault condition not hit the saw with 50+ amps before it trips. I say run a 2nd 220v outlet for the saw and a 3rd 220v for a dust collector each sized appropriately. .
    The breaker is to protect the wire, not what's plugged into it. Electricity doesn't "hit" anything with the maximum amperage; it supplies what is requested from the device using the energy. There is no electrical benefit to replacing the existing four wire receptacle and breaker for the OP's saw. Any benefit would be purely for convenience. In this case, there would actually be inconvenience because of the stated intent to use that circuit for charging an EV, too.

    That said, I do agree with adding circuits to the OP's shop space for tools like a DC which should be on dedicated service.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #14
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    Quote Originally Posted by Charles Coolidge View Post
    You want the breaker sized to your saw, you want it to trip in a fault condition not hit the saw with 50+ amps before it trips. I say run a 2nd 220v outlet for the saw and a 3rd 220v for a dust collector each sized appropriately. I have a 5hp ICS and 3hp cyclone, went with 30 amp twist lock plugs and outlets for both.
    It is NOT the responsibility of the breaker to protect whatever is plugged into the outlet! The breaker is there to protect the fixed wiring, thus preventing a structural fire. It is the responsibility of the unit plugged into the outlet to protect itself and its portable cord.

    Example: most kitchens and dining room outlets are rated at 15 amps, but they are on a 20 amp breaker (with in-wall-wiring to suit: 12 ga). This is all IAW NEC. So clearly, the breaker is not capable of protecting any appliance plugged into those outlets.

    Another example: we have dual-amperage receptacles (e.g. 15 & 20 amp plug compatible.) How would it be possible for a breaker to provide no more than 15 amps when a 15 amp device is plugged in, yet provide 20 amps when a 20 amp device is plugged in? The breaker and wire serving the outlet are required to safely handle at least the 20 amp load, while the device plugged in protects itself.

    The saw (or any other line-powered device) is required (via UL, et al) to provide overload protection to prevent a fire in any of its wiring (including inside the motor). Extension cords are protected by their receptacle not allowing anything incapable of protecting the extension cord to be plugged in.

    Generally, tools' built-in protection breakers are much faster reacting, to protect the unit from damage, and personnel from injury. Panel breakers are slower reacting, to prevent a fire (between breaker and outlet) while reducing nuisance tripping, Their reaction time is often long enough to damage the power tool if the power tool is what caused it, except for UL/CSA required protection in the tool.

    -- Andy - Arlington TX

  15. #15
    Quote Originally Posted by Jim Becker View Post
    The breaker is to protect the wire, not what's plugged into it. Electricity doesn't "hit" anything with the maximum amperage; it supplies what is requested from the device using the energy. There is no electrical benefit to replacing the existing four wire receptacle and breaker for the OP's saw. Any benefit would be purely for convenience. In this case, there would actually be inconvenience because of the stated intent to use that circuit for charging an EV, too.

    That said, I do agree with adding circuits to the OP's shop space for tools like a DC which should be on dedicated service.
    Yes the breaker is to protect the wire. Now if the wire and breaker are capable of delivering 50 amps in a fault situation then what's going to happen, there you have it.

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