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Re: CQD answer published Wednesday, January 3, 2017 -Single Receptacle Rating
1. Rreply to question on 1-2-18. The receptacle needs to comply with 406.4(A) and would need to be installed on a circuit of the same voltage and current for which it is rated unless tables 210.21(B)(2) or (3) allow different. Scott Archibald
2. I take exception to your answer on Jan.3, 2018 regarding the use of a single 30 amp receptacle being used on a 20 amp branch circuit. When installing a single 30 amp receptacle, as described in the question, the fact that the present piece of equipment does not have a FLA that requires a 30 amp branch circuit is irrelevant. Installing a single 30 amp receptacle, protected by a 20 amp overcurrent device would limit future equipment changes by the owner. One assumes that if you have a 30 amp receptacle, you have a 30 amp branch circuit supplying that receptacle. Protecting the receptacle at 20 amps, while not creating a safety issue, is poor design practice. Using NEC (2017) 210.23, Permissible Loads, In no case shall the load exceed the branch circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. By virtue of installing the single 30 amp receptacle, the installer is giving the owner an option to use future equipment that may indeed require a 30 amp branch circuit. Further justification is provided using NEC (2017) Table 210.24, the only receptacles allowed on a 20 amp branch circuit are 15 amp or 20 amp. Thank you, Tom Sieracki
Hey Scott and Tom, thanks for your comments.
Scott, you have a point that the wording in 406.4(A) does not match that of in 210.21(B)(1) so the AHJ will need to make the determination. If this is not intended then the wording in 210.21(B)(1) would (or should) state that the receptacle rating be that of the branch circuit instead of "not less than that of the branch circuit". Table 210.21(B)(2) and Table 210.21(B)(3) only apply to more than one receptacle or outlet on a branch circuit.
Tom, you also have a point and it might not be the best design but seems to follow the concept in 90.1(B) and that practice has been accepted in the past. Table 210.24 also only applies to more than one receptacle or outlet on a branch circuit.
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