20 Amp Circuit with 15 Amp Receptacle

[Alchymist]

Simple summation - the "duplex" 15 amp receptacle is allowed on a 20 amp circuit. The insides of the receptacle are rated to pass 20 amps thru itself to the next receptacle. The opening for the plug will only take a 15 amp rated plug. To my knowledge, there are no appliances with a 15 amp plug that draw more than 15 amps. If one draws in excess of 15 amps, it comes with a 20 amp plug, and cannot be plugged into a 15 amp receptacle. Can one overload a 15 amp receptacle? Of course, by plugging in TWO appliances either both in the same receptacle, or one into each of two different 15 amp receptacles on the same circuit. In neither case will the outlet be exposed to an overcurrent, as the breaker will trip.

In total: no combination of appliances having 15 amp plugs will cause the outlet to fry, the breaker will pop first. Inversely, the 15 amp plug can be plugged into a 20 amp rated receptacle, but, those same 2 appliances that caused a trip on the 15 amp receptacle will also cause a trip when plugged into the 20 amp receptacle.

 

[lakeroadster]

As per above, (as a result of its common application) the outlet innards' would need to be rated for 20A+.

Agreed... but where's the specification that requires this. It clearly states right on the outlet "15 amp".

Simple summation - the "duplex" 15 amp receptacle is allowed on a 20 amp circuit. The insides of the receptacle are rated to pass 20 amps thru itself to the next receptacle

Show me where there is a specification that all 15 amp outlets must be "rated to pass 20 amps thru itself to the next receptacle". It clearly states right on the outlet "15 amp".

And why the exception for the 15 amp receptacle, when every other receptacle has to be rated at, or above, the circuit rating?

A 50 amp outlet isn't allowed on a 60 amp circuit... that's less of a percentage than a 15 amp on a 20 amp circuit, yet that is verboten.

I'm fine with following the NEC specification. But as of yet, you can't make logic out of something that is illogical.

 

[Alchymist]

Agreed... but where's the specification that requires this. It clearly states right on the outlet "15 amp".



Show me where there is a specification that all 15 amp outlets must be "rated to pass 20 amps thru itself to the next receptacle". It clearly states right on the outlet "15 amp".

And why the exception for the 15 amp receptacle, when every other receptacle has to be rated at, or above, the circuit rating?

A 50 amp outlet isn't allowed on a 60 amp circuit... that's less of a percentage than a 15 amp on a 20 amp circuit, yet that is verboten.

I'm fine with following the NEC specification. But as of yet, you can't make logic out of something that is illogical.

If you really want the lowdown, get a copy of UL 498.

Here's a link to some receptacle info, probably more than you'd want to read:

http://iaeimagazine.org/magazine/2013/09/16/a-journey-back-to-basics-with-receptacles/

 

[sberry]

Agreed... but where's the specification that requires this. It clearly states right on the outlet "15 amp".



Show me where there is a specification that all 15 amp outlets must be "rated to pass 20 amps thru itself to the next receptacle". It clearly states right on the outlet "15 amp".

And why the exception for the 15 amp receptacle, when every other receptacle has to be rated at, or above, the circuit rating?

A 50 amp outlet isn't allowed on a 60 amp circuit... that's less of a percentage than a 15 amp on a 20 amp circuit, yet that is verboten.

I'm fine with following the NEC specification. But as of yet, you can't make logic out of something that is illogical.

The 15A rating on the recept is the plug style it will accept.

 

[Norcal]

The use of 15A receptacles on a 20A circuits has been allowed by code for ages it's not a issue if it was a problem it would be removed, so get over it.

 

[lakeroadster]

The use of 15A receptacles on a 20A circuits has been allowed by code for ages it's not a issue if it was a problem it would be removed, so get over it.

Allowing something for years doesn't make it logical.... like I said:

I'm fine with following the NEC specification. But as of yet, you can't make logic out of something that is illogical.

.... It seems that for every other circuit the receptacle rating must match or exceed the circuit rating.

 

[Alchymist]

Allowing something for years doesn't make it logical.... like I said:

Did you read the link in post 43?

 

[lakeroadster]

Did you read the link in post 43?

I did indeed, thank you for the link.

Perhaps I missed the clarification though as related to the topic at hand? Could you point out where the article defines the logic of using a 15 amp receptacle, in a 20 amp circuit, but where, per the NEC, all other circuits require the receptacle to equal or exceed the circuit rating?

It discusses testing at 150% current... but doesn't say that for a 15 amp, are they testing at 22.5 amps or at 30 amps?

Interesting article, lots of data, but doesn't appear to clarify the discussion here.

 

[sberry]

Again, it's the plug, designed to take a 15.

 

[75gmck25]

Somewhere in the documentation for most 15 amp receptacles it will state that it is rated for 20 amp pass through. It is not marked on the receptacle.

Bruce

 

[bczygan]

I don't get where it's a big deal to have 15A outlets on a 20A circuit.

Breaker protects the wire in the wall and 15A outlet sure doesn't create any risk. Neither would 20A ones like I have in my garage.

But I would ask the contractor to provide what was specified.

Bill

 

[Craptain]

One potential problem Bill is that in an overload situation there's a chance that a load might be drawing around 20A and so the wiring and breaker will be fine. But the outlet may not. It would likely get very hot, possibly enough to create a fire risk. In my experience most 15A outlets will overheat with less than 15A continuous load. I usually only buy higher quality ones these days. It's cheaper in the long run.

Sent from my LG-D801 using Tapatalk

 

[sberry]

How do others have these problems and I don't? Where do they have these "continuous" 15A loads? Considering the amount of circuits I have and the connected equipment by testimony here I should have a fire in one every week and I cant even remember the last time I had a recept issue and I use the 49 cent ones in most places, some have thousands of cycles on them.
Last one I can remember is a backstab in a mobile, a couple switches in the last 15 years.
The point of a 20A plug is simply to insure that it isn't plugged in to circuits it shouldn't, either 15;s or general 20;s with other connected equipment we do not want to interrupt with a motor start of accumulated overload and the occasional true 20A load.
I was using a big Graco sprayer in a plant, you could turn it up, do we want this on the office circuit>
Same for institutions, imagine they let the cleaning crew in a hospital plug in to other circuits. A lot of equipment draws more than 15, a 140 wire feeder draws above that at its rated output and an expert can dial it in to use 23 or 24A, comes with a 15 plug and a 14 cord. Same for small compressors and chop saws, they are not continuous and have a duty cycle rating.
Euipment that comes with a 15A plug is designed to be plugged to 20A circuits, has wire large enough not to be overheated by the appliance and to handle short circuit interruption with a 20A breaker or it had additional internal fuses, similar to Christmas tree lights today, from the plufg to fuse is cabable of 20A short and after that the tiny wires are protected with a 2A fuse.
This is why its important to use the listed breakers for many pireces o0f equipment, some have no additiona protection and is designed to rely on the breaker in the supply. Small buzzer welders being one, listed for use to 50A, 200 wire feed has additional protection after the switch, the new MVP come with a 14 cord but have stuff built in to the 50A adapter. This is why there is a warning about changing the ends to non listed ends.

 

[rlitman]

How do others have these problems and I don't? Where do they have these "continuous" 15A loads? Considering the amount of circuits I have and the connected equipment by testimony here I should have a fire in one every week and I cant even remember the last time I had a recept issue and I use the 49 cent ones in most places, some have thousands of cycles on them...

Good question. Though I work in a data center, so continuous loads are normal for me. In a residential setting, you can see continuous loads push the limits with maybe an air conditioner, or holiday lighting. That being said, you're not supposed to have more than a 16A continuous load on a 20A circuit, and that will NOT be a problem on a 15A outlet, provided it is in reasonable condition. Actually, if you look closely at the blade size of a normal NEMA 5-15 plug, they provide no less contact area than the blades on an L5-30, which is rated to carry twice that current.

When I bought my house, half the outlets were so loose that plugs would easily fall out. I did not check them with the FLIR, I just replaced them, though loose outlets can built up heat for sure. Most were replaced with the 49 cent variety (which are just fine for most uses). Tight fitting outlets should have NO trouble carrying the loads they are rated for continuously.

Heat buildup in a poor electrical connection is a self accelerating viscous cycle. Hot connections lead to loosening AND oxidation, both of which lead to more heat.

 

[sberry]

I agree specific locations such as a data center may do this and it is dedicated and under professional supervision,,, most of the time,, ha So many loads are calculated incorrectly. I have some 14 wire for lights in the ceiling, some 75 ft long. If one calculated the V drop at 15A it would be a different scenario than the 2A load that is on it. Yes, it has a 15A breaker but will never see that.
The reality is that I have worried about this endlessly especially when I was learning and still am not above a bit of over wire but in hindsight it doesn't make any difference in general use.

 

[wssix99]

Agreed... but where's the specification that requires this. It clearly states right on the outlet "15 amp".



Show me where there is a specification that all 15 amp outlets must be "rated to pass 20 amps thru itself to the next receptacle". It clearly states right on the outlet "15 amp".

And why the exception for the 15 amp receptacle, when every other receptacle has to be rated at, or above, the circuit rating?

A 50 amp outlet isn't allowed on a 60 amp circuit... that's less of a percentage than a 15 amp on a 20 amp circuit, yet that is verboten.

I'm fine with following the NEC specification. But as of yet, you can't make logic out of something that is illogical.

I bought a NEC Handbook specifically for questions like this for my build. Upon cracking it open, I have the answer - but Spock isn't going to like they way they organized this knowledge...

NEC Section 110.X, in a nutshell, states that one needs to use common sense and it's the responsibility of the installer to make sure that the equipment being installed for use is approved for use.

Section 210.21 tells the electrician that they can install "15A rated receptacle" on a "20A rated circuit." By extension, it would tell the manufacturer that they would need to build their device for such a situation and it would tell the electrician (by extension of Section 110.X) that they need to confirm that the device they are installing has also been constructed thusly.

The good news: As Alchymist points out, UL 498 exists and (as long as the outlets being installed are compliant to it) would cover all of the above parties with respect to compliance on this issue. UL 498 would just give one more comfort about an outlet - but the true definition of a "receptacle" is enough to get by the issue:

The definitions in the NEC and UL 498 clarify your concern with the rating. That 15A rating is for the receptacle. A duplex outlet is actually 2 receptacles on a single "yoke." So, in essence, that 15A outlet rating is really about the type of plug you can connect to the thing. So, two 15A "receptacles" on a single device would be rated for a total of 30A of load, but the NEC limits their use to 20A (max) circuits. Here's an interesting article that also talks about yokes: http://iaeimagazine.org/magazine/2013/09/16/a-journey-back-to-basics-with-receptacles/

UL 498 also clarifies, as I suspected above and as the Code allows, that both 15A and 20A outlets be tested to a "feed-through" amperage of 20A.

 

[lakeroadster]

If you really want the lowdown, get a copy of UL 498.

UL 498 also clarifies, as I suspected above and as the Code allows, that both 15A and 20A outlets be tested to a "feed-through" amperage of 20A.

Thanks guys... found the specification:

 

[sberry]

The 20A plug limits where it can go. A 15 when the appliance is listed limits its load (so does a power strip with 14 wire and 15 breaker) which says it can be used on any of the 15 or 20A circuits, if it can be plugged in to 15 safely due to load it wont hurt being plugged to a dedicated 20 hence the 15/20 recept but if the tool needs to be to a dedicated or allowed 20 circuit the plug limits it to those unless the janitor twists it sideways with his multi tool.

 

[sberry]

I saw a vac the other day, had a long 14 cord and a 20A end. It wasn't cause it needed 20 but didn't want it used on general classroom circuits.
I am interested now if after reading "specifications" the engineer now understands why this is safe?