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Thread: 220 V Outlet Configuration / Sawstop Question

  1. #16
    Quote Originally Posted by Andy D Jones View Post
    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
    You are missing the point entirely. Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit? Why even bother to specify the circuit for the machine at 220 20 amps, heck connect it to a 100 amp circuit by your logic. Just run some 00 wire in the shop and connect all the machines to a 100 amp circuit breaker, the wire is protected.

  2. #17
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    Quote Originally Posted by Charles Coolidge View Post
    Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit?
    Are the components in your phone charger capable of handling 20A when connected to a 20A circuit? By your logic you would need a 0.2A circuit for that. Jim and Andy are correct.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  3. #18
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    I would definitely go for a sub panel and a few extra receptacles now. Way less hassle, mess, and exspense vs doing it later in hindsight.
    Also, Iím curious why nobody has suggested changing the plug for the sawstop to the 4 prong and simply leaving the neutral slot empty on the saw side of the plug? I would think having the receptacles in the walls wired for neutral gives more flexibility long term

  4. #19
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    Quote Originally Posted by Charles Coolidge View Post
    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.
    That's not how it works, however...
    --

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

  5. #20
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    Quote Originally Posted by Charles Coolidge View Post
    You are missing the point entirely. Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit? Why even bother to specify the circuit for the machine at 220 20 amps, heck connect it to a 100 amp circuit by your logic. Just run some 00 wire in the shop and connect all the machines to a 100 amp circuit breaker, the wire is protected.
    Charles, the wire and breaker "allow" up to 50 amps to be requested without damaging the in-wall wire, receptacle and breaker. They do not "send" 50 amps of current to anything that doesn't ask for it. If your device only needs/asks for 2 amps, that's all it will ever see. Your 20 amp saw will not ask for more than 20 amps of current (outside of possible a startup spike which is normal and handled by modern breakers) and will never, ever see 50 amps of current on that circuit.
    --

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

  6. #21
    I no longer have a SawStop, but going from memory, the one I had used a motor with a thermal breaker, like most quality motors used on power tools. That is where the responsibility for protecting tool lies, not with supply circuit.

    One should never put a receptacle on a circuit with a lower rating than the wire and breaker. A 30a recpt would overheat if used to the capacity of a 50a circuit for instance. There is a common exception already mentioned,15a recepts on a 20a household circuit, that is an exception as they are rated 20a pass through and 15a for connected appliances.

  7. #22
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    Yeah, outlets don't push power, your tools suck ;-)

    We've got an RV outlet here. It's 50A as I recall. Currently (ha) disconnected to run a feed to a hot tub.

    I had a 50A circuit and outlet in my garage, presumably for a welder. I used it a couple times to back feed the main panel with a generator (yes, I turned off the main first). I rewired it to a sub panel. I think I have 1 20A, and 2 30A breakers in it. Or 2-20's and a 30? So either 70 or 80A potential draw, but if I were to load all of those to capacity it would trip the breaker in the main. Not likely I'd ever have the TS, BS, Planer, and DC all running at the same time and each pulling a real load.

    I've also got 2 outlets on each of those breakers. I kept the BS and Planer plugged in to a single circuit, but they were never run at the same time. Probably would have been fine if I started the Planer first. Had no desire, or need, to test it. But the 50A in the main would have done it's job and the beefy cable buried in the wall would have been fine.
    Last edited by Wes Grass; 06-09-2021 at 1:00 PM.

  8. #23
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    Quote Originally Posted by Ken Combs View Post
    I no longer have a SawStop, but going from memory, the one I had used a motor with a thermal breaker, like most quality motors used on power tools. That is where the responsibility for protecting tool lies, not with supply circuit.

    One should never put a receptacle on a circuit with a lower rating than the wire and breaker. A 30a recpt would overheat if used to the capacity of a 50a circuit for instance. There is a common exception already mentioned,15a recepts on a 20a household circuit, that is an exception as they are rated 20a pass through and 15a for connected appliances.
    Receptacles are required to limit the maximum size of (fixed) wire to which they can be attached, to correspond to the maximum current which they can safely handle, regardless of the physical safeguard of the receptacle itself (i.e. the current rating of any plug that can be mated with the receptacle).

    Thus you cannot physically install (and pass inspection with) a receptacle that will not safely handle the current suppliable by the breaker, if the requisite minimum size (or larger) wire is used.

    -- Andy - Arlington TX

  9. #24
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    Quote Originally Posted by Charles Coolidge View Post
    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.
    Fault current could be in the 1,000 to 1,500 ampere range regardless of whether itís a 30 or 50 ampere breaker.

    I presume itís a 30 ampere feeder which would be fine for the saw.....Rod

  10. #25
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    Quote Originally Posted by Charles Coolidge View Post
    You are missing the point entirely. Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit? Why even bother to specify the circuit for the machine at 220 20 amps, heck connect it to a 100 amp circuit by your logic. Just run some 00 wire in the shop and connect all the machines to a 100 amp circuit breaker, the wire is protected.
    It depends upon the withstand rating of the components. My 16 ampere jointer/planer is restricted to a circuit capable of not exceeding 5,000 amperes symmetrical.

    As for overload capability thatís provided by the machine, not the feeder.....Regards, Rod.

  11. #26
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    Quote Originally Posted by Charles Coolidge View Post
    You are missing the point entirely. Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit? Why even bother to specify the circuit for the machine at 220 20 amps, heck connect it to a 100 amp circuit by your logic. Just run some 00 wire in the shop and connect all the machines to a 100 amp circuit breaker, the wire is protected.
    I think you are the one that is missing the point. As someone else mentioned, breakers do not push current, tools suck current. Just because the breaker CAN supply 50 amps, it will not. If the tool draws the entire 50 amps, the breaker will let the current through. The breaker will not push 50 amps into a 20 amp saw. But 20 amp saw can draw over 50 amps if it shorts and/or catches fire, then it will trip. The saw is probably toast at this point. The breaker saves the wire in the wall and the house from burning down.

  12. #27
    The maximum overcurrent protection (MOP) is the maximum circuit breaker size required to properly protect the equipment under anticipated fault conditions...the MOP is the maximum allowable circuit breaker size that will properly disconnect power to the equipment under any anticipated fault condition.

  13. #28
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    I did not read the whole thread. I just wanted to point out that two flats @45į and a round is also the configuration for 30 amp 120V RV plugs, Just wanted to suggest that you be sure you have a 240v setup as opposed to the RV setup @ 120v.

  14. #29
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    Wow. I read most of this. OP, you need a local electricion involved who is aware if any local subtleties not covered or different from the National Electrical Code (NEC).

    Local to me I could put in a 220 VAC breaker at 50 amps, with wire suitable for 220V at 50Amps, drop that from the ceiling in my garage with a 50amp receptacle on it, and then use adapters to plug in say a planer that runs on 220VAC at 20 amps, or a different adapter to plug in a tablesaw that runs on 220VAC @ 30 amps. Within the NEC this is a kosher thing to do, but the further east you are, or the closer you are to Chicago (where they had a big fire once upon a time) the more likely you are to find local regulations more restrictive than the NEC.

    If it is legal for you to do and you have a 50amp RV outlet in your future shop, I would leave the build alone, not pay any more to the builder, and just come up with adapters to use the 50amp outlet you might already have. If it is legal. One thing I don't do is play fast and loose with my homeowner's insurance. If you have a significant claim the "adjuster" that visits your home isn't there to put a dollar value on the damage, that individual is coming over to find a reason to deny your claim.

  15. #30
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    Quote Originally Posted by Charles Coolidge View Post
    The maximum overcurrent protection (MOP) is the maximum circuit breaker size required to properly protect the equipment under anticipated fault conditions...the MOP is the maximum allowable circuit breaker size that will properly disconnect power to the equipment under any anticipated fault condition.
    Exactly. Outdoor HVAC units always have a max breaker size listed on them. They are expensive units and no one is watching them. Not all malfunctions are dead shorts which can cause an unprotected device to smolder and possibly catch fire. Installed a bath fan/infrared heating unit ceiling unit once that required a max 15 amp circuit. If you like your device you will operate it on a reasonably sized circuit even if they failed to put a max circuit size on it.
    The cell phone charger argument does not cut it. For one itís not a dumb device and two, it has small wires that would burn open very quickly resulting in no issue. Anything on a y adapter or extension cord is just plain wrong, those are temporary wiring items. Wood working tools are usually supervised so errors of judgment usually are not a problem.
    Last edited by Bruce King; 06-14-2021 at 7:01 PM.

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