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What is the rationale behind using a 20 amp circuit breaker with 12/2 cable for a circuit that only contains 15 amp duplex receptacles? I understand the rationale behind using 12/2 cable instead of 14/2 cable, but do not understand the rationale behind using the 20 amp circuit breaker instead of a 15 amp circuit breaker. Without understanding the rationale, I would assume it would be prudent to either:

  1. Replace the 20 amp circuit breaker with a 15 amp circuit breaker.
  2. Replace the 15 amp duplex receptacles with 20 amp duplex receptacles.

References to the National Electric Code would be appreciated.

Edit:

I did not intended to ask if it was permissible to use a 20 amp circuit breaker. Instead, I meant to ask "What benefit does the 20 amp circuit breaker provide if there are only 15 amp duplex receptacles?"

  • It's legal and safe to use 15A receptacles on a residential 20A circuit. The assumption is that no device in a home will draw more than 15A anyway. – isherwood Aug 2 '18 at 20:30
  • The 20A breaker is there to protect the 12/2 cabling, not the <15A appliances you plug in. – brhans Aug 2 '18 at 20:47
  • I've voted to reopen the question. You might want to write that as an answer (that's allowed here). – Harper Jul 12 at 4:52
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    @Harper Thanks for reopening the question. I removed the "answer" part of my edit, posted it as an answer, and marked it as the accepted answer. Based on your reopen and suggestion to write that as an answer, I am assuming what I described is correct. – Ryan Prechel Jul 12 at 5:09
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The 20 amp circuit breaker with 12/2 cable and 15 amp duplex receptacles allows for a total sustainable power consumption of 1,920 watts (20 amp x 80% x 120 volts) as opposed to 1,440 watts (15 amp x 80% x 120 volts). Thus, the 20 amp circuit breaker allows me to run a 1,500 watt spacer heater, a 170 watt laptop power adapter, and 2 external monitors all on the same circuit, which would NOT be sustainable with a 15 amp circuit breaker under the 80% load rule.

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This question is answered quite well here with references to the pertinent sections of the NEC: Is using 15 amp components on a 20 amp breaker against code?

In short, it's fine to use receptacles and switches rated for 15 amps on a 20 amp branch circuit with a few exceptions.

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Yes this question has been answered many time, in short as long as there are at least 2 outlets on a 20 amp circuit 2 single 15 amp or 1 duplex outlet it is legal to use a 20 amp breaker with #12 AWG wire.

  • Clarify that outlets and receptacles are two different things. There must be two receptacles to use 15-amp receptacles in a 20-amp circuit. Because there are two receptacles in a "duplex outlet" you're ok. – Jules Bartow Feb 25 at 12:02
  • Jules ., yes they are different but as long as the switch is rated for the load a 15 amp switch can even be on a 20 amp outlet, as I said in laymen terms. – Ed Beal Feb 26 at 0:08

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