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Thread: NEC Table 210.21(B)(3)

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    NEC Table 210.21(B)(3)

    I look at the above NEC Table and I find a strange inconsistency. For a circuit rating of 20A the receptacle ratings can be either 15 or 20A. Now if you look at the circuit rating of 40A the receptacle rating is either 40 or 50A. The inconsistency is that in the first case a receptacle rating of less than the circuit rating is allowed. In the second case a receptacle rating that is greater than the circuit rating is allowed. Now which case is more correct? I would say the second case. I know that this NEC Table applies to two or more receptacles on the same circuit but one can not overlook the possibility of a receptacle getting burned. If you were to plug a 20A load to a 15A receptacle protected by a 20A OCPD then you're going to have a problem.
    Eric Kench, P.E.


    If it's not broken don't fix it

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    Quote Originally Posted by erickench View Post
    I look at the above NEC Table and I find a strange inconsistency. For a circuit rating of 20A the receptacle ratings can be either 15 or 20A. Now if you look at the circuit rating of 40A the receptacle rating is either 40 or 50A. The inconsistency is that in the first case a receptacle rating of less than the circuit rating is allowed. In the second case a receptacle rating that is greater than the circuit rating is allowed. Now which case is more correct? I would say the second case. I know that this NEC Table applies to two or more receptacles on the same circuit but one can not overlook the possibility of a receptacle getting burned. If you were to plug a 20A load to a 15A receptacle protected by a 20A OCPD then you're going to have a problem.
    Most likely it's because the internal parts of a 15 and 20 amp receptacle are the same, and I can't say as I have ever seen a residential 40 amp receptacle.

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    Quote Originally Posted by acrwc10 View Post
    Most likely it's because the internal parts of a 15 and 20 amp receptacle are the same, and I can't say as I have ever seen a residential 40 amp receptacle.
    First, receptacle ampere ratings are not divided into resi and non-resi. A receptacle is the same for all installations.

    40a receps don't exist. But the Code allows 50a receps on both 40- and 50-amp circuits.

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    Well if 40A receptacles don't exist then maybe they should'nt be referenced in the code. Now what would happen if you connect a 20A load to a 15A receptacle?
    Eric Kench, P.E.


    If it's not broken don't fix it

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    Quote Originally Posted by erickench View Post
    Well if 40A receptacles don't exist then maybe they should'nt be referenced in the code.
    Make a proposal.

    Quote Originally Posted by erickench View Post
    Now what would happen if you connect a 20A load to a 15A receptacle?
    Pprobably not much, at least as far as the recep goes. The innards are the same for both 15 and 20a. The difference would be the OCD rating.

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    Quote Originally Posted by erickench View Post
    Well if 40A receptacles don't exist then maybe they should'nt be referenced in the code. Now what would happen if you connect a 20A load to a 15A receptacle?
    You would be violating 210.23(A)(1) even if it was a 20amp receptacle.

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    Quote Originally Posted by erickench View Post
    Well if 40A receptacles don't exist then maybe they should'nt be referenced in the code. Now what would happen if you connect a 20A load to a 15A receptacle?
    For one thing the 20 amp plug won't fit into the 15 amp receptacle. :rolleyes:
    Rob

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    All responses based on the 2011 NEC unless otherwise noted

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    Quote Originally Posted by infinity View Post
    For one thing the 20 amp plug won't fit into the 15 amp receptacle. :rolleyes:
    You haven't worked around to many framers have you ? He did say "load" not "plug"
    Last edited by acrwc10; 04-13-09 at 12:02 AM. Reason: add

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    Quote Originally Posted by acrwc10 View Post
    You haven't worked around to many framers have you ? He did say "load" not "plug"

    Actually he said both:

    Quote Originally Posted by erickench View Post
    If you were to plug a 20A load to a 15A receptacle protected by a 20A OCPD then you're going to have a problem.
    Quote Originally Posted by erickench View Post
    Well if 40A receptacles don't exist then maybe they shouldn't be referenced in the code. Now what would happen if you connect a 20A load to a 15A receptacle?
    Either way the 20 amp load should have a 20 amp plug which wouldn't fit into a 15 amp receptacle in the first place.
    Last edited by infinity; 04-13-09 at 05:49 AM.
    Rob

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    All responses based on the 2011 NEC unless otherwise noted

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    Quote Originally Posted by erickench View Post
    If you were to plug a 20A load to a 15A receptacle protected by a 20A OCPD then you're going to have a problem.
    No problem if you could do it.

    The manufacturers, UL and the NEC are all on board together and know that 15 amp receptacles are being installed on 20 amp circuits.

    The 15 amp receptacles and 15 amp plugs are designed with the knowledge that they will often be supplied by 20 amp circuits.

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