215.2 2014

[I-learns]

I had a question on 215.2a1 in the 2014 NEC:

• A1(a) says The conductor size shall be not less than 100% of the non-continuous plus 125% of the continuous.
• A1(b) says it shall not be less than the load to be served after the application of adjustment and correction factors.

Some are suggesting this means that when applying A1(a), that we don’t use any adjustment or correction factors but simply say it’s based on table 310.15 b16. But the text at 215.2A doesn’t say this. Logic might tell someone that they should apply adjustment favors for ambient temperature at A1 A but not detracting factors. And the use the derating factors included as part of the calculation in A1(b). However, the text doesn’t really say this.

I understand the difference in the two concerns and why they might be considered separately: one being the potential to overheat an overcurrent device and cause nuisance tripping; and the other being the potential for the conductors themselves to overheat. However, the text to the code really doesn’t seem to say that when applying A1(a) you don’t do any adjustments or correction. So how do people conclude this?

 

[don_resqcapt19]

I agree that the language in (A)(1)(a) is wrong and have submitted proposals to make a change the last two code cycles, by they have been rejected by the Code Making Panel. The CMP refuses to use the defined term "ampacity" as it is defined in Article 100 for this rule. In all cases, the definition of that term requires that the ampacity adjustment and/or correction factors be applied any time the term is used. That is not what the CMP is doing in this section.

The intent of the CMP is that you use the ampacities direct from the ampacity table for (A)(1)(a). For (A)(1)(b) you apply any required ampacity adjustment and/or correction factors.

 

[david luchini]

I agree with Don about the language. I don't know why they changed it in the first place...it made more sense in the versions prior to 2014.

Reasons people might conclude that you don't apply adjustment/correction factors to A1(a):
1) They remember how to calculate the feeder size prior to 2014
2) A1(a) doesn't mention adjustment/correction factors, where A1(b) does.
3) The sections states the conductors shall be sized for the larger of A1(a) or (b): If the correction/adjustment factors were applied to both A1(a) and A1(b), then A1(a) would always be larger. The requirement to select the larger of the two wouldn't make any sense.
4) The examples in Annex D follow this convention.

 

[wwhitney]

5) While not an Article 100 term, the phrase "allowable ampacity" is always used in a way that refers to the tables in Article 310, whose titles start off "Allowable Ampacities . . ."

(at least 95% true, I looked at all the usages in Chapter 2 and 3 in the 2017 NEC)

Cheers, Wayne

 

[don_resqcapt19]

5) While not an Article 100 term, the phrase "allowable ampacity" is always used in a way that refers to the tables in Article 310, whose titles start off "Allowable Ampacities . . ."

(at least 95% true, I looked at all the usages in Chapter 2 and 3 in the 2017 NEC)

Cheers, Wayne

Not any more...they don't use that in the titles of the tables in the 2020 code. Also the conditions that apply to the table ampacites are no longer in the tables.

You go to section 310.16 for the conditions, and the to Table 310.16 for the numbers. The title is now " Table 310.16 Ampacities of Insulated Conductors with Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried) "

 

[david luchini]

Not any more...they don't use that in the titles of the tables in the 2020 code. Also the conditions that apply to the table ampacites are no longer in the tables.

And it looks like they made the wording of 215.2(A)(1) worse.

 

[wwhitney]

Not any more...they don't use that in the titles of the tables in the 2020 code. Also the conditions that apply to the table ampacites are no longer in the tables.

Yes, now that I look, 2020 seems like a step backward in this regard.

You and I both submitted PIs for 2023 to address this language, hopefully one of them will be accepted.

Cheers, Wayne

 

[I-learns]

I agree with Don about the language. I don't know why they changed it in the first place...it made more sense in the versions prior to 2014.

Reasons people might conclude that you don't apply adjustment/correction factors to A1(a):
1) They remember how to calculate the feeder size prior to 2014
2) A1(a) doesn't mention adjustment/correction factors, where A1(b) does.
3) The sections states the conductors shall be sized for the larger of A1(a) or (b): If the correction/adjustment factors were applied to both A1(a) and A1(b), then A1(a) would always be larger. The requirement to select the larger of the two wouldn't make any sense.
4) The examples in Annex D follow this convention.

_{David, seems like you are saying you think one SHOULD apply the correction and adjustment factors to A1(a). Is this what you are saying? I didn’t think we should but I struggled understanding how the text wouldn’t require someone to, even though according to videos that Mike Holt has posted online, he says the 2014 change was exactly to clarify that you didn’t need to do this.}

 

[david luchini]

_{David, seems like you are saying you think one SHOULD apply the correction and adjustment factors to A1(a). Is this what you are saying?}

No. Where did you read that? I gave a list of reasons not to apply the correction/adjustment factors to A1(a).

 

[don_resqcapt19]

_{David, seems like you are saying you think one SHOULD apply the correction and adjustment factors to A1(a). Is this what you are saying? I didn’t think we should but I struggled understanding how the text wouldn’t require someone to, even though according to videos that Mike Holt has posted online, he says the 2014 change was exactly to clarify that you didn’t need to do this.}

They said that was the reason for the 2014 change, but as long as they continue to use the defined term "ampacity" in (A)(1)(a) the code making panel has the language incorrect.

The code making panel insists that the language they are using is clear that you do not apply the ampacity adjustment and or correct factors to (A)(1)(a).

It is clear to me that the actual language requires the application of those factors. However, in this case the CMP has made the intent of the rule clear, and we need to apply the intent and not what the language says.

Maybe next code cycle they will accept a Public Input that will make the code language say what the code making panel thinks it says.