Possible Pattern w/ 110.14(C) and 310.15(B) ... Check My Math, What Do You Think?

[don_resqcapt19]

@don_resqcapt19
...

...but don't sit there and try to gaslight me like this. I can read English and I know how an IF statement works. As far as the explicit text of 310.15(B) is concerned, I'm solidly convinced I'm reading it correctly and I would wager my last red cent that if I brought this book to anyone else outside the forum, they would agree with me. Nothing will convince me otherwise.

...

As I said before, I have ZERO interest in your opinion, or anyone else's opinion on what the sections you are question really say, and there is NOTHING that will change my reading of what the sections say. That is why I did not continue the technical debate on this issue.

 

[Jerramundi]

As regards the second paragraph of 2017 310.15(B) (or 2020 310.15(A)), it's an "if foo then bar" statement. We all agree on that.

Do we? You seem to understand what I'm talking about, but no others do.

I stand by my interpretation of 310.15(B) that the IF statement is a conditional statement which must be satisfied in order to grant us permission to derate from the temperature column of the conductor... and that because it is more restrictive than the permission ranted by 110.14(C), it supersedes it.

Everyone other than you and I, seem to be saying that 310.15(B) tells you to take the 60*C ampacity if, post derating from 90*C, if the derated ampacity is not less than the 60*C ampacity.

If that happens to be the case, due to some other section of code, or field experience, than so be it.

But as far as the explicit text of 310.15(B) is concerned, it says nothing of the sort.

The question is what happens when "not foo"? That paragraph doesn't say, so I don't see how you can say we are reading that particular paragraph differently than you. You are just using a different assumption about the default "not foo" case.

I agree that this is the question that needs to be answered... and IMO, more explicitly addressed in the text of the NEC.

I do think there are couple points that are not stated sufficiently explicitly in the NEC that should be:

(1) Circuit ampacity = minimum (termination limit ampacity, conductor ampacity)

As far as 310.15(B) is concerned, I agree.
This is addressed by 310.15(A)(2)... but that does not change the fact that the text of 310.15(B) still has an issue.

 

[Jerramundi]

As I said before, I have ZERO interest in your opinion,

Fine by me buddy.

That is why I did not continue the technical debate on this issue.

And yet, here you are, posting.

 

[Jerramundi]

Why would you want it to go below the 60° C ampacity? You take the 90° C ampacity (25 amps) and apply to the derating factor.

For example 6 CCC's would be 25 amps*70%=17.5 amps good on a 15 amp OCPD. Are you saying that it is more complicated than that?

I'm not revisiting this. Read the rest of the thread. @wwhitney has correctly identified my valid point of contention.

 

[infinity]

I'm not revisiting this. Read the rest of the thread. @wwhitney has correctly identified my valid point of contention.

Fair enough. I'll join the others by saying that you're incorrect and leave it at that.

 

[Jerramundi]

Fair enough. I'll join the others by saying that you're incorrect and leave it at that.

False.

Not per the explicit text of 310.15(B).
Per industry SOP, perhaps. But not that particular block of text.

 

[wwhitney]

I stand by my interpretation of 310.15(B) that the IF statement is a conditional statement which must be satisfied in order to grant us permission to derate from the temperature column of the conductor... and that because it is more restrictive than the permission ranted by 110.14(C), it supersedes it.

That's not how rules stack.

If earlier in (2017) 310.15 were a statement of the form "when applying ampacity correction and adjustment, the base ampacity shall be the lesser of the insulation temperature rating and the termination temperature rating" then we would need the permission granted by (2017) 310.15(B) second paragraph. But we don't have any such statement, so we don't need the permission granted.

A statement of the form "A shall be permitted if B" doesn't imply "A shall not be permitted if not B." So if not B, we just ignore the second paragraph.

Basically the second paragraph paragraph of 310.15(B) is a badly worded way of saying "remember that when the adjusted and corrected ampacity starting from the insulation temperature rating exceeds the unadjusted/uncorrected ampacity at the terminal temperature rating, the latter limit still applies."

Cheers, Wayne

 

[winnie]

My understanding, backed up by things such as textbook and the NEC handbook, is that you are required to calculate at each point along the conductor, calculate the ampacity at that point, and then take the minimum anywhere along the conductor as the ampacity.

So if you have a 60C termination, then you use the 60C ampacity. Terminations are not in conduit, so there is no derating for CCC, but there might be ambient temperature adjustments.

In the middle of the conduit the only thing present is the conductors and their insulation. So you might need to adjust for ambient or derate for CCC, but you can use the insulation temperature rating.

So much for the common understanding of the code. With that said, I think Jerramundi might be correct in a literal read of 310.15. Personally my plan is to ignore this; the common reading is well supported in the community and makes physical sense.

Jon

 

[Jerramundi]

That's not how rules stack.

If earlier in (2017) 310.15 were a statement of the form "when applying ampacity correction and adjustment, the base ampacity shall be the lesser of the insulation temperature rating and the termination temperature rating" then we would need the permission granted by (2017) 310.15(B) second paragraph. But we don't have any such statement, so we don't need the permission granted.

Word games. The lack of such a prior statement does not change what 310.15(B) says.

A statement of the form "A shall be permitted if B" doesn't imply "A shall not be permitted if not B." So if not B, we just ignore the second paragraph.

Yes it does. It is its' logical contrapositive.

Now, if you wanted to make the argument that, like a computer program, since the condition was not satisfied, we cannot take the action that it was giving us permission to perform, and THEN we "ignore the paragraph," and "the program continues to run..." I suppose you could argue that.

But you can't just throw away the reality that 310.15(B) explicitly requires permission to perform this function based on a condition which must be satisfied (at least the way it is current worded does).

So the question then becomes, can we just defer back to 110.14(C) which gives us permission to utilize a higher temperature conductor for correction and adjustment? I'm of the understanding that when there are conflicting rules, the most restrictive is king.

If you wanted to argue that since we failed to satisfy that condition, so we cannot perform the function, and now must look for our answer elsewhere, such as 110.14(C)(1)(a)(2), which gives us permission to utilize a higher temperature conductor, but requires us to set the ampacity at the 60*C mark, I would accept that logic.

But the follow-up problem to that is, we have not performed the required corrections and adjustments, but merely satisfied 110.14(C)(1)(a)(2)

Basically the second paragraph paragraph of 310.15(B) is... badly worded...

Agreed

 

[winnie]

If the calculated ampacity of a conductor is 22.5A, what code is violated when only 10A actually flows in the conductor?

Jon

 

[Jerramundi]

My understanding, backed up by things such as textbook and the NEC handbook, is that you are required to calculate at each point along the conductor, calculate the ampacity at that point, and then take the minimum anywhere along the conductor as the ampacity.

So if you have a 60C termination, then you use the 60C ampacity. Terminations are not in conduit, so there is no derating for CCC, but there might be ambient temperature adjustments.

In the middle of the conduit the only thing present is the conductors and their insulation. So you might need to adjust for ambient or derate for CCC, but you can use the insulation temperature rating.

So much for the common understanding of the code. With that said, I think Jerramundi might be correct in a literal read of 310.15. Personally my plan is to ignore this; the common reading is well supported in the community and makes physical sense.

Jon

I'm not trying to be a... *insert descriptor of choice.*
But as far as the literal read of 310.15(B) is concerned, I can't just walk away from this, lol.

If you all are taking the position that industry SOP supports what you're saying, that's fine. It wouldn't be the first time that this the case.
However, if we are indeed talking about a literal read of 310.15(B), I cannot concede, yet....

 

[Jerramundi]

The code is my Bible, but it was written by man.
Sometimes you gotta go with industry SOP. For example, many villages require permits for any and all electrical work, but few people pull them.
I pulled one one time for a single circuit upgrade. The inspector looked so peeved when he arrived, hahaha.

 

[wwhitney]

So if you have a 60C termination, then you use the 60C ampacity. Terminations are not in conduit, so there is no derating for CCC, but there might be ambient temperature adjustments.

As to the last point, my understanding is that the NEC, as commonly understood, does not require ambient temperature correction at terminations, but I do not have a satisfactory explanation as to why it does not. Any thoughts?

Cheers, Wayne

 

[wwhitney]

Yes it does. It is its' logical contrapositive.

No, it's not the contrapositive, it's the converse. Which is not logically equivalent to the statement, and is not legally implied.

The contrapositive of "if B, then A shall be permitted" is "if A is not permitted, then not B."

Cheers, Wayne

 

[Jerramundi]

No, it's not the contrapositive, it's the converse. Which is not logically equivalent to the statement, and is not legally implied.

The contrapositive of "if B, then A shall be permitted" is "if A is not permitted, then not B."

Cheers, Wayne

Fair enough, but we are still skipping 310.15(B) because we have failed to satisfy the conditional statement within.

 

[tom baker]

If 14 AWG is practically obsolete, why will the 2023 NEC allow 14 AWG CC protected by a 10 amp OCPD?

I did not see a reply to this, I am curious as to your comments

 

[Jerramundi]

@wwhitney The only way I see industry SOP working out, via explicit code references and your argument that the converse of 310.15(B) is not legally applicable, is the following...

310.15(B)
- Failed to satisfy conditional statement, derating not permitted from 90*C from THIS explicit section
- Defer back to 110.14(C)

110.14(C)
- Permission to derate from 90*C granted, action performed.

310.15(A)(2)
- Select lower ampacity of 60*C rating.
- Ignore exception, not required to apply it.

110.14(C)(1)(a)(2)
- Ampacity required to be set at 60*C rating satisfied.

Either way, it's logic circles and the code should be more clear, IMO.

 

[Jerramundi]

I did not see a reply to this, I am curious as to your comments

You could put a 1A CB on #14 AWG. I don't know of any code section that would prohibit this.
My issue is not with utilizing larger wire than required.
My issue is with an explicit, literal reading of 310.15(B) paragraph #2.

I was saying, if my literal read of 310.15(B) was accepted... then on 60*C terminals, you would derate #14 AWG from 90*C until you got it below 15A and then it would be obsolete as a solution for a 15A circuit.

But now that I think about it, I don't know of any code sections that explicitly require a 15A circuit. 20A sure, but not 15A.
Manufacturers might require it, but not the NEC that I'm aware of.

Per my read of 310.15(B), all #14 AWG THHN (or other 90*C wire), when on 60*C terminations and derated from 90*C, would be placed on 10A breakers, less they satisfied 240.4(B) and fed a single receptacle and could then be placed on 15A CB's.

 

[Jerramundi]

@tom baker ... and I see how this read of 310.15(B) contradicts everyday SOP. Fully acknowledged.

 

[ramsy]

I don't know of any code sections that explicitly require a 15A circuit.

Sorry if I didn't get the question, but see 240.4(D)(3&4) if you need code that requires 15A circuits.

240.4(D) also prohibits the "Next Size Up" rule 240.4(B) on these small conductors, which include #10 wire, limited to 30A, except when other articles apply as listed in table 240.3