Rubber Cord Ampacity

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wwhitney said:
Lengthy text isn't going to fit on a small product. So you'd like it to have some special symbol that in the manufacturer's literature is explained to mean that the device has been listed for use with conductors having ampacities other than those listed in T310.15(B)(16)?

Cheers, Wayne
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Yes, and that does happen. There are markings shown in the UL White Book for some products that work like that for that very reason.
 
I have not heard from Mr. Mercier but I did receive this


While I am not Mr. Mercier ( who is a good friend of mine as you know) I can offer my understanding of the applications for Table 400.5 and how it related to 110.14(C)(1) if interested.


1) While the ampacity of the Flexible Cord and Cable can be selected from T400.(A)(1) or (2) depending on the cord or table type, it is going to be limited to the compliance of Section 100.14(C)(1) where applicable.

For example, let's say I had 60 amps of continuous load and 45 amps of noncontinuous load on a circuit that is being terminated to a circuit breaker. The math would be 60 amps@ 125% and 45 amps for a load of 120 amps. Now, per 110.14(C)(1)(b) which states that I must reference the 75C column of T310.15(B)(16) and gives no reference to T400.5(A)(1) or (A)(2).

As a result the smallest sized CU wire I can have for the 120A load is 1 AWG @ 75C which gives us 130 Amps of capacity. So why the table in Article 400....

These cable types are assumed to be installed in applications where there is adequate space and free air. Because of these anticipated installation conditions, overheating from being enclosed in a small space is not a large concern. Therefore, these cables are permitted to carry more current per gauge size compared to cable and wire types mentioned in NEC 2014 Section 310 Conductors for General Wiring, which typically are installed in applications with limited air space or air movement.

2) Their increased ampacity is useful for many things (for example voltage drop and so on) with the understanding that 110.14(C) will still always apply. Now, if the terminals to a specific application are rated for the use with the specific cord then it will be evaluated as listed and identified for use with the specific cable in question. Very frequently you have specific cables with finely stranded conductors that are rated for a much higher ampacity than its equivalent in T310.15(B)(16) but it is being used with a specific piece of equipment evaluated for such a cable and listed and identified as such.
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Dennis, I goofed up and hit the edit button, I did not actually edit your post. :ashamed1:


Now that said, can anyone explain how the increased capacity shown in article 400 helps with voltage drop?:huh:


2) Their increased ampacity is useful for many things (for example voltage drop and so on)
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oldsparky52 said:
Just so I'm clear on your position, are you of the opinion that 110.14(C) is not requiring cord/cables to use Table 310.15(b)(16) ampacities for terminations? (I'm assuming you read 110.14(C) ).

The way I read 110.14(C) all terminations no matter what Table you can use for ampacities of the cable or conductor are limited to Table 310.15(B)(16).

I hope someone can show me how this is incorrect interpretation.
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I haven't read the entire thread so if I am recovering territory please forgive me<<

The argument I would attempt to make is along the following lines:

The ampacities for Rubber cord come from T400.(A) 1 or 2---

110.14(C)1 references 310.15(b)(16)---

Since rubber cord is not a 310.15(b)(16) wiring method therefore that section does not apply therefore you use T400 so that Yes you can
use this and protect it at 250 Amp.

This might also be best used along with some coffee and doughnuts for misdirection.
 
I believe it was suppose to say that the increase ampacity of the conductor is like helping with voltage drop.....it helps for the " possible use of it in a condition where it is not being used as free air ...and not really voltage drop.
 
RichB said:
I haven't read the entire thread so if I am recovering territory please forgive me<<

The argument I would attempt to make is along the following lines:

The ampacities for Rubber cord come from T400.(A) 1 or 2---

110.14(C)1 references 310.15(b)(16)---

Since rubber cord is not a 310.15(b)(16) wiring method therefore that section does not apply therefore you use T400 so that Yes you can
use this and protect it at 250 Amp.

This might also be best used along with some coffee and doughnuts for misdirection.
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The issue is the rule in 110.14(C) limiting you to the Table 310.15(B)(16) ampacities at the terminations.
 
Dennis Alwon said:
I have not heard from Mr. Mercier but I did receive this
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Leave it to the fine members of your forum to find one statement in parenthesis that was just an example of why larger sizes can have benefits like increasing sizes for voltage drop in general are used and blow it out of context while ignoring the actual statement in the sentence. Typical.
 
MasterTheNEC said:
Leave it to the fine members of your forum to find one statement in parenthesis that was just an example of why larger sizes can have benefits.
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Except the idea referenced wasn't about larger sizes of copper, it was about higher ampacities for a given size of copper. Which doesn't help with voltage drop, so the parenthetical comment doesn't make sense. It definitely made me go "huh?" when I read it.

Cheers, Wayne
 
Quite without wishing to put anyone down, a comment like that in a reply to a question raises some doubt about the quality of the rest of the answer.
 
MasterTheNEC said:
Leave it to the fine members of your forum to find one statement in parenthesis that was just an example of why larger sizes can have benefits like increasing sizes for voltage drop in general are used and blow it out of context while ignoring the actual statement in the sentence. Typical.
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You is a member as well, if not you couldn't post here.
 
Dennis Alwon said:
I don't understand the other way around. We are using 3/0 conductor rated 240 map- next size 250 amps- if the panel is rated for a 250 amp breaker than why can I not use the 3/0 cord which is rated 240@ 75C..:?

I must be missing something here
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Dennis, I think you have the proper understanding of this. If the termination is rated, for example, for conductors sized from #1/0 through 350mcm, then the termination is rated for 310A at 75C. The rating of the termination doesn't change if you connect a #3/0 versus a 300mcm.
 
david luchini said:
Dennis, I think you have the proper understanding of this. If the termination is rated, for example, for conductors sized from #1/0 through 350mcm, then the termination is rated for 310A at 75C. The rating of the termination doesn't change if you connect a #3/0 versus a 300mcm.
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The termination is rated at 310A at 75C when using a conductor sized in accordance with Table 310.15(B)(16). It is not rated for a conductor that exceeds the ampacity rating of Table 310.15(B)(16).
 
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