Conductor ampacity

[wwhitney]

I would said 85A. Because 110.14 (C) Temperature limit. 95A can be used for adjustment, correction or both.

I don't have an opinion, as I'm not a fan of the "only one ampacity" point of view. But under that point of view, an alternative interpretation would be that the termination has an ampacity of 85A, while the wire would still have an ampacity of 95A.

A related question is whether this distinction ever matters for some other NEC requirement that uses the word ampacity.

Cheers, Wayne

 

[wwhitney]

I think we need to agree on what termination previsions are, as I posted earlier the original proposal of110.14(C) is good place to check, it can be found in the 1993 A1993 Technical Committee Reports (TCR) [Articles 90- 250]

Agreeing would be nice. The original PI you reference (thanks for the pointer) uses the the term "termination provisions" in a way that is consistent with it meaning "terminals or other connection means provided by the manufacturer". Likewise AALZ.

But the problem is that 110.14(C) as adopted does not use "termination provisions" in that fashion. The problematic paragraph is:

"The determination of termination provisions of equipment shall be based on 110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.12."

One doesn't "determine" a terminal; one could "determine" the ampacity associated with a terminal, or with a wire landing in a terminal. If you'll agree that the meaning of the above paragraph is unchanged by the following edits, then I can agree that with those edits, "termination provisions" means "terminals, etc".

The determination use of termination provisions of equipment shall be based on 110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is listed and marked otherwise, conductor ampacities used in determining with equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.12.

Cheers, Wayne

 

[tortuga]

Simplifications are made to permit ease of administration and understanding by the general use. I have encountered this with multiple PIs to expand the allowances to 705.12(B). In the last round the CMP's response to my proposals was to paraphrase "you're probably right on the physics, but we're not going to further complicate 705.12(B). You can do what you want under 705.12(B)(6)'s "under engineering supervision" provision."

That was a poor decision by the CMP to punt on your proposal like that, it would have made lots of peoples jobs easier not more complicated.

If there is a comparable "under engineering supervision" provision applicable to your example and 110.14(C), then as an engineer you could reasonably stamp a design for the use of 2/0 Cu conductors for a 200A load in your example, or 1/0 Cu for a 185A load.

310.14 has a provision for engineering supervision.

 

[tortuga]

One doesn't "determine" a terminal;

If I am building a 100HP 690 volt motor and I need to select the motor leads and terminal blocks am I not "determining" the termination provisions? Where do I look for guidance on that as its not listed equipment? 110.14(C)(1)
If I purchase a 100HP 690 volt motor and the manufacturer has already determined the termination provisions I do not need to re-determine them per 110.14(C)(1).

 

[wwhitney]

If I am building a 100HP 690 volt motor and I need to select the motor leads and terminal blocks am I not "determining" the termination provisions?

Sure that's true for "termination provisions = terminals, etc."

But is building a motor under the purview of the NEC? I don't think so. And so I don't think 110.14(C)(1) is telling you how to size terminals in case you want to build some equipment. It is instead imposing limits on how you use the terminals provided on equipment you install, in particular on how much current you can put through the combination of the wire you install and the terminal on the equipment.

110.14(C)(1) is just elaborating on how you determine the temperature rating of equipment terminals to comply with the first sentence of 110.14(C): "The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device." Likewise, 110.14(C)(2) is elaborating on how you do that for "Separately installed pressure connectors".

These two pieces of text are subdivisions of 110.14(C) because they are both related to the preceding paragraph of 110.14(C). You can't understand 110.14(C)(1) without considering it in the context of the parent 110.14(C) text.

Cheers, Wayne

 

[tortuga]

Sure that's true for "termination provisions = terminals, etc."

But is building a motor under the purview of the NEC? I don't think so.

Why would it not be? The NEC can have a say in how equipment is put together, 430.7 has instructions on how to mark a motor, 430.12 has requirements on the terminal housing UL can't override that, thats not for the installer thats for the motor builder.
Same with HVAC equipment;
Where in the code does it require motors or HVAC equipment to be UL listed?
424.6 requires some HVAC type equipment to be listed, like a duct heater, but a field installer may assemble - mix and match components to make a final HVAC system, and would they not need to size a terminal block?

And so I don't think 110.14(C)(1) is telling you how to size terminals in case you want to build some equipment.

110.14(C)(1) applies when you need to determine termination provisions of equipment, the literal opening sentence, if someone has not done that then use that section.
What make this confusing is most of the time 110.3(B) and 110.14(C)(1) will lead you to the same place, but whats important to know is how you got there.

 

[wwhitney]

Why would it not be?

Sure, the NEC has some requirements for motors when they are installed under its jurisdiction. I agree if you're building a motor for installation under the NEC, you better meet those requirements.

So let me rephrase: 110.14(C)(1) was not put in the NEC to help people select their terminal size when building equipment. I traced the introduction of the first paragraph of 110.14(C)(1) with its garbled usage of "termination provisions" to PI 1-227 (Log #3285) for the 2002 NEC (PDF page 72 of 70-A2001-ROP.pdf from nfpa.org). In the 1999 NEC, every use of the term "termination provisions" in 110.14(C) was consistent with its meaning "terminals, etc." (I suggest you read that version.) But the above PI introduced the "determination of termination provisions" language that is problematic.

The point of the PI was to introduce the language about Table 310.16, as well as an incidental renumbering. Below is the substantiation for the PI; it speaks well for itself. The ROP says the PI was accepted and does not provide a panel statement.

Cheers, Wayne

Substantiation for PI 1-227 (Log #3285) for the 2002 NEC

"The objective of this proposal is to clear up confusion relative to what ampacities are used to determine the proper conductor size at equipment terminations. When 600V and less equipment is evaluated relative to the appropriate temperature characteristics of the terminations, conductors sized based on Table 310-16 are used. The UL General Information Directory (pages 1 and 2) clearly indicates that the 60C and 75C provisions for equipment have been determined using conductors from Table 310-16. However, if an installer or designer is not aware of the UL guide card information, they may attempt to select conductors based on the Tables other than 310-16. This is especially true if a wiring method is used that allows the use of ampacities such as those in 310-17. This can result in overheated terminations at the equipment. Clearly the ampacities shown in other tables (such as 310-17) could be used for various conditions that the wiring method is subject to (ambient, ampacity correction, etc.) but the conductor size at the termination must be based on ampacities from Table 310-16.

This proposal does not have any new impact on the equipment or wiring methods; it simply adds a rule from the listing information into the Code because it is an installation and equipment selection issue.

In addition the proposal provides for a slight renumbering to easily accommodate the reference to the Table and adds titles to the Level 2 subdivision as required by the NEC Style Manual."

 

[Solar Guy]

NEC says the conductor ampacity to be terminated must be based on table 110.14 C 1

However a wire by itself without termination appears to have an ampacity equal to any table from 310.16, 310.17 etc etc but when do you often have a wire that is not terminated to use these other tables?

The only example I know of, is an overhead feed to a weatherhead service drop that enters a conduit: You are going from free air to a multi-conductor conduit, so the wire size at that point should be larger that the free air feeders.

 

[wwhitney]

In the 1999 NEC, every use of the term "termination provisions" in 110.14(C) was consistent with its meaning "terminals, etc." (I suggest you read that version.)

Here it is below as an image (sorry the website renders the image so large).

I think this version is clearer than the 2023 version, other than the lack of the reference to Table 310.16. In fact, the only difference in content (as opposed to renumbering) between 1999 NEC 110.14(C) and 2023 NEC 110.14(C) is the one paragraph that is now the first paragraph of 110.14(C)(1), with its confusing phrase "determination of termination provisions."

Cheers, Wayne

 

[tortuga]

I have read all of them, and they all state they are not trying to change anyhting about the existing UL standards.
Its interesting, what the code said back then is what would be enforceable for installations made then.
Note the lack of a reference to a ampacity table AND the 600V and less.
My example in post 181 demonstrates the difference between then and now, over 600V VS over 1000V.
Back then my example 690V pole mounted fused cutout in free air would be a over 600V system and fall under 110.40 , now its 1000V or less.
The UL green book does not exist anymore and may UL, CSA and IEC standards have dramatically changed since '93.
For 'charlies rules' 110.14(C)(1) says what is says now, and I read it literally to mean how the determination is done but not that I always have to do it.

 

[wwhitney]

I have read all of them, and they all state they are not trying to change anyhting about the existing UL standards.

OK, and what the UL standards say matches my lightly edited version of 110.14(C) in post #222. I foresee a PI in 2029 NEC.

It is unfortunate the non-standard use of the term "termination provisions" was introduced in the 2002 NEC, but in the context of those UL standards, and the history of 110.14(C), it is clear that 110.14(C)(1) has nothing to do with the field electrician selecting terminals, and is only about limitations on the ampacity of conductors landed on terminals of equipment.

If "termination provisions" were a defined term, I'd have a much harder time arguing the above, but it is not. [Also the problem would hopefully not have persisted for 20 years.] So we have to infer the meaning of it from how it is used to come up with a reasonable result.

Cheers, Wayne

 

[tortuga]

OK, and what the UL standards say matches my lightly edited version of 110.14(C) in post #222. I foresee a PI in 2029 NEC.

It is unfortunate the non-standard use of the term "termination provisions" was introduced in the 2002 NEC, but in the context of those UL standards, and the history of 110.14(C), it is clear that 110.14(C)(1) has nothing to do with the field electrician selecting terminals,

What problem would it solve to take guidance out of the code for a field electrician, motor winding shop or panel builder ?
I bet the CMP would just delete 110.14(C)(1) entirely for four reasons:

• The trend in the code is to delete all the dot 100 sections and add dot 6 relegating electricians to installers of listed equipment and require every last ziptie to be UL listed, which will end up just costing consumers.
• The problem it intended to solve went away, electricians are more aware than ever of 110.3(B) and following the directions included with equipment, most have smart phones to look up missing info or instructions the customer might have lost.
• The standards themselves have changed, those old concerns were with cablebus and MI cable (1999 change).
• The 601 - 1000V dead band where 90C terminations are standard.

The way I see it when wiring equipment in 2025 you have two routes to the same happy place with 110.14(C) to select
"the temperature rating associated with the ampacity of a conductor as to not exceed the the lowest temperature rating of any connected termination, conductor or device":

• Follow the instructions and markings on listed equipment 110.3(B)
• Determine it yourself using 110.14(C)(1)

 

[wwhitney]

I don't have an opinion, as I'm not a fan of the "only one ampacity" point of view. But under that point of view, an alternative interpretation would be that the termination has an ampacity of 85A, while the wire would still have an ampacity of 95A.

A related question is whether this distinction ever matters for some other NEC requirement that uses the word ampacity.

240.21(B)(2) is a case where it matters whether 110.14(C) is imposing a limit on the wire ampacity, or is just imposing an additional limit on the wire size via some sort of "termination ampacity" consideration. Because 240.21(B)(2) imposes a limit on the "ampacity of the tap conductors". If 110.14(C) doesn't change the ampacity of the wire, then you can use the 90C ampacity of 90C insulated wire when determining compliance with 240.21(B)(2).

But I believe the typical interpretation is that 110.14(C) does impose a limit on the wire ampacity, and thus one is limited to using the 75C ampacity at the overcurrent protection device to satisfy 240.21(B)(2)(2).

Cheers, Wayne

 

[ggunn]

240.21(B)(2) is a case where it matters whether 110.14(C) is imposing a limit on the wire ampacity, or is just imposing an additional limit on the wire size via some sort of "termination ampacity" consideration. Because 240.21(B)(2) imposes a limit on the "ampacity of the tap conductors". If 110.14(C) doesn't change the ampacity of the wire, then you can use the 90C ampacity of 90C insulated wire when determining compliance with 240.21(B)(2).

But I believe the typical interpretation is that 110.14(C) does impose a limit on the wire ampacity, and thus one is limited to using the 75C ampacity at the overcurrent protection device to satisfy 240.21(B)(2)(2).

Cheers, Wayne

When you are saying "a limit on wire ampacity", I assume you mean a lower limit.

 

[wwhitney]

When you are saying "a limit on wire ampacity", I assume you mean a lower limit.

Well yes, the termination is typically rated 75C, while the conductor is typically rated 90C, and the 75C ampacity is less than the 90C ampacity.

Cheers, Wayne

 

[ggunn]

Well yes, the termination is typically rated 75C, while the conductor is typically rated 90C, and the 75C ampacity is less than the 90C ampacity.

Cheers, Wayne

I figured as much, but "limit" to me implies an upper bound. YMMV.

 

[wwhitney]

I figured as much, but "limit" to me implies an upper bound. YMMV.

As a mathematician, that sounds non-standard to me. Limit just means an inequality, be it an upper or lower bound. : - ) And in other usage, too, like Lower Explosive Limit and Upper Explosive Limit.

But you can see 110.14(C) as imposing an upper bound on the ampacity of a given wire size, if the 75C tabular ampacity applies to the wire. Or you can see it as imposing a lower bound on the wire size.

Cheers, Wayne

 

[ggunn]

As a mathematician, that sounds non-standard to me. Limit just means an inequality, be it an upper or lower bound. : - ) And in other usage, too, like Lower Explosive Limit and Upper Explosive Limit.

But you can see 110.14(C) as imposing an upper bound on the ampacity of a given wire size, if the 75C tabular ampacity applies to the wire. Or you can see it as imposing a lower bound on the wire size.

Cheers, Wayne

Ah, a mathematician. That explains a lot.

"Speed limit" doesn't usually mean you must drive that fast, but I guess you could try that argument with a State Trooper.

 

[wwhitney]

"Speed limit" doesn't usually mean you must drive that fast, but I guess you could try that argument with a State Trooper.

You occasionally see speed limit signs that say "max 65 mph min 45 mph." But yes, this is a usage where "speed limit" usually means a maximum. Whereas if you saw a "height limit" sign at an amusement park, it usually means a minimum.

Cheers, Wayne

 

[ggunn]

Near Houston on Interstate 10 the signs might as well read "Minimum speed limit 85mph".