15 amp outlet

LarryFine

Master Electrician Electric Contractor Richmond VA
Why is it acceptable to install 15amp outlets on a 20 amp 12 awg circuit?
Because no single receptacle is expected to max out the circuit.

Added: Remember that the receptacle rating describes the slot configuration, not the conductive parts' ampacity.

Most 15a and 20a receptacles of a given grade contain the same internal parts.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
In the pic, note that the receptacle on the right, the Triple-wipe Contacts in the red box, you can see that either a horizontal or vertical blade will fit, and be touched in three places by the internal conductive parts. All they have to do to make a 20a version and/or a 250v receptacle, is put on a different front face, either vertical, horizontal or T-shaped for each slot:

 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You can only use 15 amp receptacles on a 20 amp circuit when there is more than one receptacle. A single 15 duplex would be code complaint because it is two receptacles.
 

powerpete69

Senior Member
Location
Northeast, Ohio
Occupation
XXX
15 amp receptacles have the vertical blades for the hot and neutral. A 20 amp receptacle accepts the vertical and horizontal slot.
That being said, a plug with vertical slots is made to pull a max of 15 amps from the manufacturer.
A plug pulling up to 20 amps with have the horizontal slot.

Back to the 15 amp duplex receptacle, either receptacle in the box can handle at least 15 amps, but your 20 amp breaker will trip around 20 amps.
So in other words, nothing can start on fire in this situation.
 

Carultch

Senior Member
Location
Massachusetts
Why is it acceptable to install 15amp outlets on a 20 amp 12 awg circuit?
15A = what it can deliver to one particular plug, connected to the socket.
20A = what #12Cu wire in its terminal screws can withstand, and what can be passed to the next receptacle(s) in the same branch circuit.

The 20A part of the rating is standard among 15A receptacles, because it is expected that you will put several on the same branch circuit, and deliver no greater than 15A to any individual plug. That's by design, because a load taking more than 15A requires a different shaped plug. Therefore, 15A receptacles can be used on both 15A and 20A branch circuits. 20A receptacles have a dual slot to fit both specialty 20A plugs of heavy duty loads, and common 15A plugs.
 

winnie

Senior Member
A different, but related question is 'why are we allowed to plug a 1A lamp into a 15A receptacle on a 20A circuit. IMHO the answer is somewhat circular.

15A receptacles are allowed to be installed on 20A circuits, and thus are _designed_ to be installed on 20A circuits. Similarly low power loads are _designed_ to be safe with a 15A plug configuration on a 20A circuit.

I expect that if code did not permit this install, then manufacturers would make the 15A receptacles slightly cheaper and would not test them on 20A circuits.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
Similarly low power loads are _designed_ to be safe with a 15A plug configuration on a 20A circuit.
A 1A lamp probably has a 18 AWG cord (max 10 amps) or a 16 AWG cord (max 13 amps) and no internal fusing. A high resistance short may heat the cord to cherry red without tripping the breaker. A hot cord can set carpet, drapes, and loose papers on fire. Happens on power strips too. We allow it because it makes this things economical, but I wouldn't say it's inherently safe.

overloaded power strip.png
 
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PaulMmn

Senior Member
Location
Union, KY, USA
Does... or did... that power strip also have surge protection built in? Many power strips use MOVs, which are sacrificial parts that give up a little of their life with each surge. And several have been implicated in power strip meltdowns and fires.

Also looks like at least 3 devices will need new cords...
 
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