Overcurrent Protection for 16 AWG Extension Cords

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Jim Reizner

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I do not understand how 16 AWG extension cords (cord sets) are considered protected by a 15 ampere or 20 ampere circuit breaker. I know this is OK, but I just don't see where the NEC (or UL 817) allows this.

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2020 NEC 400.16 Overcurrent Protection (for Flexible Cords and Flexible Cables) says: "Flexible cords not smaller that 18 AWG, and tinsel cords or cords having equivalent characteristics of smaller size approved for use with specific appliances, shall be considered as protected against overcurrent in accordance with 240.5."

2020 NEC 240.5(B)(3) Protection of Flexible Cords, Cables and Fixture Wires / Branch Circuit Overcurrent Device / Extension Cord Sets says: "Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements."

I do see where 2020 NEC 240.5(B)(4) says "20-ampere circuits - 16 AWG and larger" but this is only for "Field Assembled Extension Cord Sets."

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The label on such an extension cord (6 feet long) that I have says: "16 Gauge, 13 Amp, 125 Volt."

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The applicable UL Standard is UL 817 Cord Sets and Power-Supply Cords.

UL 817 Table 114 Cord Ampacities and Voltage Ratings shows these type of cords at 13 amps up to 50 feet, and 10 amps over 50 feet.

UL 817 Table 115 Cord-Set Ratings shows for 15 amp up to 50 feet a 14 AWG would be required, more than 50 feet a 12 AWG would be required. For 20 amp up to 50 feet a 12 AWG would be required, more that 50 feet a 10 AWG would be required.

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What am I missing?
 
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Jim Reizner said:
The label on such an extension cord (6 feet long) that I have says: "16 Gauge, 13 Amp, 125 Volt."
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Based on the cord label information that you've provided I'm guessing that it's up to the user of the cord to decide if it's the right size for the job.
 
My Question:

"Where in the NEC does it allow a 16 gauge flexible cord (happens to be an extension cord/ cord set) - to be protected by a 15 or 20 amp circuit breaker?"

(I provided a lot of additional references in my original question).
 
Jim Reizner said:
My Question:

"Where in the NEC does it allow a 16 gauge flexible cord (happens to be an extension cord/ cord set) - to be protected by a 15 or 20 amp circuit breaker?"

(I provided a lot of additional references in my original question).
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Your thread title says "extension cords" which are plugged into a receptacle based on the configuration of the male plug (UL 817). As far as I know there is nothing in Article 400 that would apply directly to an portable extension cord. Now if you're using a flexible cord under Article 400 then 400.10 and 400.12 will tell you their permitted and prohibited usage.
 
I really wish someone would actually read the original question I have and answer it for me.

2020 NEC 240.5(B)(3) does apply to extension cords.

It's actually a pretty straight-forward question. Unfortunately I don't think the answer is that easy - as I could not find it.
 
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The higher than expected rating may be do to the cord typically is used on the ground where a lot of it is exposed to free air thereby dissipating heat better than if it was in conduit or buried.
 
Actually it is quite simple. The 16ga cord is not protected against overload by the 15 or 20A breaker. It is protected against a short circuit.
UL, in evaluating the extension cord, makes the assumption that it will not be deliberately or inadvertently overloaded. After all, there is a warning on the packaging! :)
You can also get 18ga extension cords which are even less protected against overload.
The alternative is put fuses in all of the cord connectors, sized appropriately to the wire capacity (the British method).
 
oldsparky52 said:
The higher than expected rating may be do to the cord typically is used on the ground where a lot of it is exposed to free air thereby dissipating heat better than if it was in conduit or buried.
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It "may" be because of any number of things. We don't go on "may's" - we go by what the NEC says. That is what I am looking for.

Also - the NEC and UL understand that extension cords are typically used in free air, yet they (NEC and UL) still rate 16 AWG flexible cords and extension cords at 3 amps.
 
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GoldDigger said:
Actually it is quite simple. The 16ga cord is not protected against overload by the 15 or 20A breaker. It is protected against a short circuit.
UL, in evaluating the extension cord, makes the assumption that it will not be deliberately or inadvertently overloaded. After all, there is a warning on the packaging! :)
You can also get 18ga extension cords which are even less protected against overload.
The alternative is put fuses in all of the cord connectors, sized appropriately to the wire capacity (the British method).
Click to expand...

OK, but where in the NEC does it say anything like that? I prefer to go by what the NEC has to say on a topic, not on what others think.

2020 NEC 240.5(B)(3) Protection of Flexible Cords, Cables and Fixture Wires / Branch Circuit Overcurrent Device / Extension Cord Sets says: "Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements."

It says "protected" - not protected against overloads.

16 AWG flexible cords are rated at 13 amps [2020 NEC Table 400.5(A)(1)] and at 13 amps per UL 817 Table 114.

So how can they be "protected" by a 15 amp or 20 amp circuit breaker?

And no - UL 817 requires extension cords / cord sets of 18 or 17 AWG to have their own protection "rated equal to or less than the ampacity of the flexible cord" (per UL 817, part 21.1).

I am not arguing that we should go to the British method where we have fuses in our plugs, I simply want to find out where in the NEC this is allowed.

It has to be hidden somewhere between the NEC and UL 817, because we all do this all the time. I have not been able to find this - neither has anyone else so far.
 
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Jim Reizner said:
Because it does. See 2020 NEC 240.5(B)(3) "Extension Cord Sets." This is my third tome mentioning that.
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Sorry I'm a little slow today. The cord is listed, it has (as you mentioned in your OP) a label on it which is part of the listing, that label tells you its rating which is consistent with the code wording in 240.5(B)(3). It also has a molded cord cap that is based on its listing. A 15 amp cord cap is permitted to be plugged into a receptacle a 20 amp circuit.
240.5(B)(3) Extension Cord Sets.
Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements.
Click to expand...
 
Jim Reizner said:
It "may" be because of any number of things. We don't go on "may's" - we go by what the NEC says. That is what I am looking for.

Also - the NEC and UL understand that extension cords are typically used in free air, yet they (NEC and UL) still rate 16 AWG flexible cords and extension cords at 3 amps.
Click to expand...

Correction - 13 amps.
 
infinity said:
Sorry I'm a little slow today. The cord is listed, it has (as you mentioned in your OP) a label on it which is part of the listing, that label tells you its rating which is consistent with the code wording in 240.5(B)(3). It also has a molded cord cap that is based on its listing. A 15 amp cord cap is permitted to be plugged into a receptacle a 20 amp circuit.
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The listing and the label for the extension cord set is 13 amps (which is the normal rating for 16 AWG). How is that protected by a 15 or 20 amp breaker? (Not what someone thinks / guesses, what the NEC or UL 817 says.)

I know that a 15 amp plug is allowed to be plugged into a receptacle on a 20 amp circuit, that has nothing to do with the question.

Restating the question again:

Where in the NEC (or UL 817) does it say we can use a 16 AWG extension cord on a 15 or 20 amp circuit?

(The way I read 2020 NEC 240.5(B)(3) - this would not be acceptable. We would need to protect that 16 AWG extension cord to 13 amps. I obviously am missing something, as we use 16 AWG extension cords on 15 and 20 amp circuits all the time.)
 
Does this help

240.5(B)

(4) Field Assembled Extension Cord Sets. Flexible cord used
in extension cords made with separately listed and installed
components shall be permitted to be supplied by a branch
circuit in accordance with the following:
20-ampere circuits — 16 AWG and larger
Click to expand...
 
Jim Reizner said:
Restating the question again:

Where in the NEC (or UL 817) does it say we can use a 16 AWG extension cord on a 15 or 20 amp circuit?
Click to expand...
It does not say that you can or you cannot. I cannot find it and you haven't been able to find it either because it doesn't exist in the NEC. As you stated in the OP 240.5(B)(3) is as close as you can get. If the extension cord is listed and has a 15 amp plug on the end then it can be used on either a 15 or 20 amp circuit. It would help if the NEC explicitly stated the requirements (20 amp circuits) like it does for field assembled cords sets in 250.5(B)(4) in 250.4(B)(3) but it does not.

I don't have access to UL817 so I can't comment as to whether or not that will answer your question. Is this question related to a specific application?
 
Dennis Alwon said:
Does this help
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Thanks for taking the time to look at this, Dennis.

I already noted that NEC reference my original question.

No, it does not help because "regular" extension cord sets are not field assembled. BUT if 240.5(B)(3) had a statement like this, or if one like it could be found elsewhere in the NEC or in UL 817 that WOULD solve the dilemma I am having.

Thanks again for your time and consideration!
 
One last comment: The NEC says that they "should be considered to be protected", not that they are protected. In essence the NEC is saying, other ampacity calculations and practical effects notwithstanding, not to worry about it.
 
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