15amp receptacles on 20amp cicuits

[Jim Leedham]

I do inspections on newer condos from time to time and I keep finding 15 amp receptacles on 20 amp circuits. Is this typically allowed as far as electrical codes go? Should it be corrected? I had one person tell me that it was o.k. because the shape of the plug for a 20 amp device will not fit in a 15 amp receptacle. But what if multiple devices are plugged into the outlet and collectively draw more then 15 amps? Seems like that could cause a problem.

[Michael Larson]

As long as 12 gauge wire is being used you're fine.

This is not code, but commentary from the NEC Handbook.

"A single receptacle installed on an individual branch circuit must have an ampere
rating not less than that of the branch circuit. For example, a single receptacle on a 20-
ampere individual branch circuit must be rated at 20 amperes; however, two or more
15-ampere receptacles or duplex receptacles are permitted on a 20-ampere generalpurpose
branch circuit. This requirement does not apply to specific types of cord-andplug-
connected arc welders."

15 amp duplex receptacles are rated at 20 amps pass through in the UL listings. And each 1/2 of the duplex is rated at 15 amps. So they can handle a 15 and 5 or 10 and 10 amp loads for example.

[Jim Port]

You might want to read NEC 210.21. and specifically 210.21(B)(1) and (B)(3).

If someone tries to use too many items and they all add up to too many amps the breaker will trip. No different than 20 amp devices on a 20 amp circuit.

I have yet to see a 20 amp cord configuration in a residential setting. Window shaker A/C might be the only thing I could even think might have that plug.

[Jim Leedham]

Thanks guys, much appreciated.

[Marcel Gratton]

Originally Posted by mlarson

however, two or more 15-ampere receptacles or duplex receptacles are permitted on a 20-ampere general purpose branch circuit.

Is a kitchen counter top receptacle considered a general purpose branch circuit...

Beside, where would I plug my welder when creating fusion dishes and flambées?

Jim,

Some microwave oven's have 20 Amps plugs.

Cheers,

[Robert Meier]

The requirement is that when 2 or more 15 amp receptacles are used they are permitted on a 20 amp circuit. By definition one 15 amp duplex receptacle is two receptacles so therefore it qualifies as the required two or more 15 amp receptacles on the 20 amp circuit. As mentioned 15 amp duplex devices are rated for 20 amps of feed through current.

A single receptacle alone on a circuit must have an ampacity of not less than the circuit OCPD. So a 50 amp single receptacle would be permitted on a40 amp circuit. This is typically seen in a single family dwelling where the range circuit is wired for 40 amps but a 50 amp receptacle is used.

[Marcel Gratton]

You cannot plug a 20 amp appliance (t-plug) into a 15 amp receptacle therefore is safe but plugging a 50 amp appliance into a 40 amp circuit to me doesn't appear safe.

I reported a 50 amp receptacle protected by a 40 amp breakers /8 gauge wiring in a garage as being over fused just last week.

[Michael Larson]

Marcel,

40 amp protection for 8 gauge wire is OK.

[Robert Meier]

Originally Posted by mgratton

I reported a 50 amp receptacle protected by a 40 amp breakers /8 gauge wiring in a garage as being over fused just last week.

Although it may seem counter intuitive it is permitted. Reporting it as being overfused would be incorrect when applying the requirements of the NEC. I used the range receptacle/circuit as an example because standard 120/240v, single phase receptacles are only manufactured in 30 and 50 amp configurations. For a 40 amp circuit you would need to use a 50 amp receptacle/cord combination. Here's the relevant article:

210.21 Outlet Devices.
Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B).
(A) Lampholders. Where connected to a branch circuit having a rating in excess of 20 amperes, lampholders shall be of the heavy-duty type. A heavy-duty lampholder shall have a rating of not less than 660 watts if of the a medium type, or not less than 750 watts if of any other type.
(B) Receptacles.
(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.
Exception No. 1: A receptacle installed in accordance with 430.81(B).
Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.
FPN: See the definition of receptacle in Article 100.

[Marcel Gratton]

Thanks for the explanation, it is much appreciated.

Regards,