20 Amp outlets vs 15 Amp outlets on 20A circuit

Discussion in 'Electrical Forum discussion & Blog' started by DIYorBust, Jul 27, 2020.

  1. wwhitney

    wwhitney Well-Known Member

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    More like if your shower is 2 gpm, and you run one line for your bathroom group, that line better be at least 2.5 gpm, in case someone uses the lavatory while the shower is running.

    Cheers, Wayne
     
  2. DIYorBust

    DIYorBust Active Member

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    I think it's the opposite of that. They're saying make sure you don't plug in a 15 amp appliance to a 15 amp outlet. That's like saying, make sure you don't let your shower use the full 2gpm because if someone plugs something else in, it could be too much for the circuit.
     
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    FWIW, a device that actually draws 15A would not pass UL certification with a 15A plug on it!
     
  4. DIYorBust

    DIYorBust Active Member

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  5. wwhitney

    wwhitney Well-Known Member

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    One what? That cord is 16AWG and is rated 13A. So the user is supposed to ensure that what is plugged into it does not exceed 13A.

    Cheers, Wayne
     
  6. wwhitney

    wwhitney Well-Known Member

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    I don't think that's true. There are plenty of 15A hair dryers out there with 15A plugs.

    Cheers, Wayne
     
  7. DIYorBust

    DIYorBust Active Member

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    Ok here's one without that limitation:

    https://www.amazon.com/dp/B000Y4DXLA/
     
  8. wwhitney

    wwhitney Well-Known Member

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    That one's 14 AWG and so is rated at 15 amps.

    As to your OP, here's one that's 12 AWG, but the rating is still 15A: https://www.amazon.com/dp/B073ZN7PN9 That's presumably because of the 15A plug on it, so you're not supposed to load it more than 15A.

    But as a practical matter, if the receptacle is on a 20A circuit, and the receptacle wipers are rated for 20A (unknown), then I would think everything would work fine at 20A with a 12 AWG extension cord, even if the rating is only 15A. I expect that any extension cord/multi-tap with a 20A rating on it would have a 5-20 plug (probably a rare beast).

    Cheers, Wayne
     
  9. DIYorBust

    DIYorBust Active Member

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    A little more digging, and I find that while the NEC ampacity table lists the ampacity of 14awg wire at 20A, it is required to be on a 15A or lower breaker, and 12awg is rated for 25A, but is required to operate on a 20A breaker, and there is a similar requirement for #10. Why is there this distinction? Perhaps it is an extra safety margin for overloading or ambient temperature, but larger conductors do not have this extra margin. So it seems like a good bet that whatever they are allowing for those 15A outlet wipers can easily handle 20A, and very likely more than that.

    I am merely speculating here, but we know already this is allowed by code, so the speculation is only as to why it is allowed and whether I personally feel this is safe enough for my use.
     
  10. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    What most people tend to forget, or simply don't know, is that a 15A duplex receptacle, regardless of how cheap, is TWO 15A receptacles on a common device yoke. The device is rated for 20A, and BOTH receptacles are rated for 15A. It IS NOT a "15A rated device".
     
  11. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Can you elaborate on this?
     
  12. wwhitney

    wwhitney Well-Known Member

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    To be a bit more precise, those are the 75C ampacities. The 90C ampacities are even higher, while the 60C ampacities are the familiar 15A/20A/30A. NM cable is restricted to a final ampacity not to exceed the 60C ampacity, even though it has 90C conductors inside.

    Also, the small conductor rule 240.4(D) requires OCPD not exceed the 15A/20A/30A numbers in most cases. One exception is for motor circuits.

    Cheers, Wayne
     
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