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

[wwhitney]

Not moot. Feels that way out of frustration, just like talking about privacy in today's world does,
but if it were to result in an ampacity below the 60*C level, then it is definitely NOT moot.

I meant moot for a single cable. At least until some manufacturer comes out with 10/7 NM cable, then the CCC derating limits it to 28A.

Cheers, Wayne

 

[Jerramundi]

So if a manufacturer comes out with 12/5 NM cable, you can stuff (2) of those through a firestopped hole, and the CCC derating is based on 5 (each cable separately), not 10. But if you stuff 3 of them in the hole, the CCC derating is based on 15.

Cheers< Wayne

Still curious about this one... Did I miss something in this little tangent about NM?

 

[wwhitney]

Still curious about this one... Did I miss something in this little tangent about NM?

334.80 second paragraph begins with "Where more than two NM cables . . .". So with only two cables, there's no need to treat the cables collectively, rather than individually. But Table 310.15(B)(3)(a) refers to "number of conductors in the raceway or cable . . .", so any cable with 5 CCCs is subject to a 0.8 adjustment factor. Which for a single NM cable only matters if there is also a temperature correction factor to be applied. (NM is only available in sizes up to #2 Cu, and for those sizes, 0.8 * (90C base ampacity) > 60C base ampacity.)

Cheers, Wayne

 

[infinity]

I just want to clarify my initial example. I should have said 2 cables with 6 CCC's. That stops the other requirement to derate for than 3 CCC's in a cable.

 

[acrwc10]

When I read through this it sounds like the OP is looking at the conductor to limit amperage to protect the device and not the ocpd as the protection.

 

[Jerramundi]

When I read through this it sounds like the OP is looking at the conductor to limit amperage to protect the device and not the ocpd as the protection.

Well, to be clear, I'm fully aware that the conductor itself does nothing to limit current in the way that we're looking to achieve that here.
I'm still just talking about the calculated, allowable max ampacity of a conductor in all of this.

A #10 AWG THHN 90*C conductor on its' own still has an allowable ampacity of 40A (+/- depending on conditions), but relying on the calculated allowable max ampacity to meet the temperature limitations of 110.14(C) to provide an element of protection... and THEN turning to OCPD selection for the final, most important element of protection.

You're less likely to damage terminations if you have a calculated allowable ampacity below their threshold,
than if you do above it, at least, that's how I see it.

 

[Jerramundi]

Just to back peddle a little bit and try to wrap this up...

Right, I think this is the only real point of disagreement now. The sentence in 310.15(B) doesn't really tell us what to do when "the corrected and adjusted ampacity does exceed the ampacity for the temperature rating of the termination in accordance with the provisions of 110.14(C)."

While I will agree that this is true - there are no explicit instructions describing this case.
However, as I've said before, when looking at conditional statements such as if statements, they work in a certain way.

For example (and pardon me for the crudeness of the following, it's been years...)

If ( A^{CorrectedAndAdjustedFrom90*C}<=A^60*C ) {
A^{CorrectedAndAdjustedFrom90*C} = A^{Final, Less OCPD Selection} }
}
Else {
...and to your point, this is what is explicitly lacking.
}

But the point I'm trying to make is, you can't just skip to the second line of code.

The if statement is a conditional statement which grants us permission to perform correction and adjustment from the 90*C column, the code just words it funny, IMO, with a weird, seemingly pointless comma in the middle of it all.

Note that we don't need that 310.15(B) language to have the permission to use the higher temperature rating of the conductor as the basis for ampacity correction and adjustment, as 110.14(C) already provided that permission. 310.15(B) is just reminding us of that.

Fair point that 110.14(C) has already granted us permission, but the way I understand how the code works, is that there are going to be conflicting sections and that in such a case, the most restrictive rule is king, in which case, the conditional if statement of 310.15(B) would supersede the permission granted by 110.14(C)

So when the corrected and adjusted ampacity does exceed the termination ampacity, we just use the lesser value, the termination ampacity. I.e. in your OP, the red boxes are not violations, they are just cases where the ampacity is limited by the termination to 30A. I agree this isn't spelled out, but it is how it is commonly understood...

Roger that. If you say this is how it is commonly understood to be, I will take that into consideration and I do appreciate the discussion we've had and your patience and communication. The overall discussion, especially regarding 110.14(C), was helpful.

I was really hoping someone would have found a way to explicitly explain this to me with the code, because unfortunately, as far as safety and liability are concerned, I need to have explicit reasoning for my decisions and I feel my interpretation of 310.15(B) can be defended explicitly, whereas the other interpretation cannot.

I would feel more comfortable deferring to correcting and adjusting from the 75*C column, given that the conductor is also listed as a 75*C conductor.

I will agree, that common sense wise, if the corrected and adjusted is not below the 60*C threshold, simply setting it at the 60*C threshold makes partial sense, because you're taking the allowable ampacity down even further than what derating from the 90*C column was able to achieve.

I still feel like this should be re-written if this is the case, because this is NOT how I understand if statements to work.

 

[Jerramundi]

@wwhitney One would think it would/should be simpler... 60*C termination = 60*C conductors = derate from 60*c ampacity...
but then we've entered the realm of utilizing #10's for typical, simple 20A circuits and #14 is well, practically obsolete.

 

[wwhitney]

For example (and pardon me for the crudeness of the following, it's been years...)

If ( A^{CorrectedAndAdjustedFrom90*C}<=A^60*C ) {
A^{CorrectedAndAdjustedFrom90*C} = A^{Final, Less OCPD Selection} }
}
Else {
...and to your point, this is what is explicitly lacking.
}

But the point I'm trying to make is, you can't just skip to the second line of code.

No one is skipping the second line of code, we all agree on that branch. We are saying that the intention is:

If ( A^{CorrectedAndAdjustedFrom90*C}<=A^60*C ) {
A^{Final, Less OCPD Selection} = A^{CorrectedAndAdjustedFrom90*C}
}
Else {
A^{Final, Less OCPD Selection} = A^60*C
}

Or more simply A^{Final, Less OCPD Selection} = MIN(A^{CorrectedAndAdjustedFrom90*C}, A^60*C )

Wayne

 

[Jerramundi]

@wwhitney Not skipping the second line of code... skipping TO the second of code.
Just trying to explain how I read the permission granted by 310.15(B) as conditional.

I understand what you all are saying. Message received.
However, I would still argue, that the actions taken by your else statement are not explicitly granted by the sections of code that we are discussing.
Not trying to be difficult, just explaining my position.

I guess we're at an impasse with that part. However, I appreciate your input on the matter and will take your interpretation in consideration.

 

[Jerramundi]

I'm beginning to look at this and see the impracticality of my interpretation.

I re-worked the numbers for 60*C terminations and derating #12 AWG THHN from 90*C.
It pretty much ends up being the case, that if I do any sort of derating, even a slight ambient temperature correction, for a simple 120V, 20A circuit... I'm losing #12 AWG as a solution for a 20A circuit for even the most basic of applications, like general purpose receptacles.

The ONLY way I can see to make my interpretation work, which I still believe this is how the code reads, would be to find either:
(1) 75*C or 90*C rated general purpose receptacles... and I see nothing of the sort... anywhere...
(2) Utilize #10AWG for general purpose receptacle circuits... and that just flies in the face of all of my experience.

Thank you to everyone who was patient and ran through discussing this with me. Applying 110.14(C) is a relatively new idea to me.
It didn't appear in my licensing exam and I've never once heard anyone that I worked for mention it even once.

If I can find the time to do so, I feel a PI for 310.15(B), as @wwhitney suggested, would be a good idea.
Can anyone provide me with information on how to do so?
I think the way the NEC has utilized the if statement here is contradictory to what you all claim is SOP.

 

[infinity]

One would think it would/should be simpler... 60*C termination = 60*C conductors = derate from 60*c ampacity...
but then we've entered the realm of utilizing #10's for typical, simple 20A circuits and #14 is well, practically obsolete.

I'm curious as to why you feel that this would be simpler? The derating is used so that the temperature rating of the conductor is not exceeded and that the conductor is not damaged from heat. If the conductor has 90° C insulation why would using 60° C for derating make sense? Not sure what you mean about #14 being practically obsolete.

 

[tom baker]

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

 

[don_resqcapt19]

...

If I can find the time to do so, I feel a PI for 310.15(B), as @wwhitney suggested, would be a good idea.
Can anyone provide me with information on how to do so?
I think the way the NEC has utilized the if statement here is contradictory to what you all claim is SOP.

The submission process for the 2026 will open this fall after the publication of the 2023 code. It is a very simple online process.

After the 2023 code is published, go to nfpa.org/70 and select next edition. When the process is open for Public Inputs, there will be a box that says "submit public input" (or some wording to that effect). You click that and follow the instructions. You will need to provide a technical substantiation as to why you see a need for the code language to change. You will also have to decide what section needs too be changed to accomplish your goal. You can make multiple PIs to different sections if you see a need to change rules in more than one section.

I would not expect the Code Making Panel to make any change as this is long standing code and no one else has ever suggested the code does not say what all of the rest of us see it as saying.

If they resolve (reject) your PI, you will have a chance for rebuttal in the Public Comment stage. PCs are submitted after the First Draft Report is published on the NFPA site in a process that is really they same as the PI process but based on the First Draft Report and not the previous edition of the code.

If they do not accept your PC, you have a very short period of time after the publication of the Second Draft Report to submit a "Notice of Intent to Make a Motion (NITMAM). If the NFPA accepts that notice, it would become a Certified Amending Motion (CAM) that would be debated on the floor of the NFPA meeting to adopt the 2026 NEC. You would only do that if you, or your representive is going to attend that meeting as someone has to be present to make the motion and defend your position.

 

[Jerramundi]

I'm curious as to why you feel that this would be simpler? The derating is used so that the temperature rating of the conductor is not exceeded and that the conductor is not damaged from heat. If the conductor has 90° C insulation why would using 60° C for derating make sense? Not sure what you mean about #14 being practically obsolete.

It was just spoken out of frustration with 110.14(C) and 310.15(B)...
Upon initial investigation of these sections, one would think 60*C listed equipment would require 60*C listed conductors and require derating from 60*C.

60*C = 60*C = 60*C... especially because everyone in the industry that I've interacted with, pretty much just goes by the 60*C column to avoid any headaches. Prior to getting into the code for myself, I never knew #12 AWG THHN had any ampacity other than 20A.

The #14 AWG being obsolete was conditional upon my interpretation of these sections being valid.
If we had 60*C terminations, derated #14 AWG THHN from 90*C, and were required to get it below the 60*C threshold, it could never be utilized for a 15A load or have a 15A breaker on it (less it was serving a single receptacle).

On that note, I did have a supposed building official tell me recently that they were requiring #12 for all branch circuits,
even short run general purpose. Go figure.

 

[Jerramundi]

@don_resqcapt19 appreciate the information on the PI procedure.

I would not expect the Code Making Panel to make any change as this is long standing code and no one else has ever suggested the code does not say what all of the rest of us see it as saying.

As for this, I still 150% disagree that I'm reading 310.15(B) incorrectly (less my version of the Handbook having a potential misprint).

Perhaps your interpretation comes from additional knowledge outside of this particular section, such as combining it with 210.3 or another section, or something you learned in the field that trained you to interpret 310.15(B) this way... and that's fine if that's the case...

...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.

None of which is to say that I don't appreciate the input or that I won't be taking all of the knowledge shared here into consideration.
You can close this thread now.

 

[don_resqcapt19]

It was just spoken out of frustration with 110.14(C) and 310.15(B)...
Upon initial investigation of these sections, one would think 60*C listed equipment would require 60*C listed conductors and require derating from 60*C.

60*C = 60*C = 60*C... especially because everyone in the industry that I've interacted with, pretty much just goes by the 60*C column to avoid any headaches. Prior to getting into the code for myself, I never knew #12 AWG THHN had any ampacity other than 20A.

The #14 AWG being obsolete was conditional upon my interpretation of these sections being valid.
If we had 60*C terminations, derated #14 AWG THHN from 90*C, and were required to get it below the 60*C threshold, it could never be utilized for a 15A load or have a 15A breaker on it (less it was serving a single receptacle).

On that note, I did have a supposed building official tell me recently that they were requiring #12 for all branch circuits,
even short run general purpose. Go figure.

They can only do that if they have a legally adopted amendment to the NEC.

 

[Jerramundi]

They can only do that if they have a legally adopted amendment to the NEC.

Yes, I'm aware how local amendments work. I was just sharing that I was told this by a building official and found it interesting.

Still, not sure I would have the cojones to challenge a building official on something like this. Not sure it's worth the headache.
Big job, multi-unit building, where that $/ft adds up to be significant, sure. But for a few circuits, I would just go ahead and do the #12.

 

[wwhitney]

...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 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. 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 mean, I think the NEC could delete that paragraph without any change in overall meaning. The rest of 310.15 tells you how to come up with the adjusted and correct ampacity, and 110.14(B) tells you about the termination temperature limits,

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)
(2) Temperature correction does not apply for termination ampacity.

Cheers, Wayne

 

[infinity]

The #14 AWG being obsolete was conditional upon my interpretation of these sections being valid.
If we had 60*C terminations, derated #14 AWG THHN from 90*C, and were required to get it below the 60*C threshold, it could never be utilized for a 15A load or have a 15A breaker on it (less it was serving a single receptacle).

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?