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In one of the bedrooms all of the duplex receptacles are 20 amps. Do I need a 20 amp switch?

Also, I have a garage which is about 30 feet from the house and the wire that goes underground is either 10 or 12 gauge. Do I need a 20 amp switch for that? I always thought that if you have 12 gauge wire the receptacles or switches should always be 20.

Also since my garage is all 12 or 10 gauge do the switches in the garage have to be 20 amp? I know NEC makes exception to this rule, but what is the correct thing to use?

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    What size is the wire and breaker? I have found homes that someone liked the look of the 20 amp receptacles but the wiring and breaker were 14 gauge & 15 amp. – Ed Beal Feb 21 '17 at 3:15
  • You've made the assumption that the lighting is on the same circuit as the outlets. This may not (and often is not) the case. – isherwood Feb 21 '17 at 14:23
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Due to a special exception (NEC 210.21.B.3), you are allowed to use 15A receptacles (plural) on a 20A circuit. In order to be UL listed, all 15A receptacles must prove they can handle 20A in all respects (except 15A to any one plug, since that still means 15A).

Almost every 120V receptacle is a duplex (double). If you have a simplex (single) 120V/15A receptacle, that is special. As Ed Beal notes, since only one thing can be plugged in and it must be <=15A, the breaker must be 15A. NEC 210.21.B.1.

if you switch a hardwired load, the switch only needs to be rated for the hardwired load.

If you switch a single receptacle, the switch must be rated for the maximum of that receptacle (perhaps 15A). If one switch controls two or more receptacles, you could plug anything in there, and the switch must be rated for whatever the breaker is rated for.

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  • If only a single 15 amp receptacle it must be a 15 amp breaker not 20 other than that I agree. – Ed Beal Feb 21 '17 at 17:13
  • @EdBeal good catch! – Harper - Reinstate Monica Feb 21 '17 at 17:16
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NEC 404.14 snap switches shall be used within their ratings. resistive and inductive loads not exceeding the rating at the applied voltage. 404.14.F where used to control outlets the switch needs to be rated not less than the breaker (ocpd).

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  • I think I misunderstood - good I am not an electrician:) So I have 20A breakers and 12# wiring all throughout, but I used 15A duplex receptacles for the most part. 20A light switches were near impossible to find and I didn't see the sense in that either since lighting rarely approaches an Amp for me. is it that I have 2 options to be within code? 1) replace all the 15A receptacles with 20As (not sure if the light switches are necessary) 2) replace the 20A breakers with 15A breakers. sorry if I am hijacking the OP's question but maybe others have done the same as I have. – ecco88 Feb 21 '17 at 18:18
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Short answer: It has to be rated to the breaker.

  • If the breaker is 20A, use #12 wire and 20A receptacles.

  • If the breaker is 15A, use #14 wire and 15A receptacles.

Of course with a 15A breaker you can still oversize the wire to #12 and devices to 20A capacity, but it doesn't do much other than prepare the circuit for a future 20A breaker.

Detailed answer: The breaker should be equal to or less than the ampacity ratings of everything else on the circuit. Think of it as the intentional weak link. If an overload occurs, you'd rather have the breaker trip first as against the receptacle/light/etc. burn out.

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    Oversizing wire also protects against voltage drops on long cable runs. – user4302 Feb 22 '17 at 16:37
  • @Snowman Right too, most residential cases won't apply. – TFK Feb 22 '17 at 17:12

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