110.14(C)(1) Conflicting Information?

[xptpcrewx]

I am dealing with a piece of equipment with aluminum load lugs "marked" but not necessarily "listed" for use with 12 AWG through 3/0 AWG conductors...

When applying 110.14(C)(1), what is the limiting temperature rating that should be used? (60 or 75 deg C?)
With the way the language is currently written 110.14(C)(1)(a) and 110.14(C)(1)(b) can both apply. For example:

110.14(C)(1)(a) applies because the termination provisions are marked for 14 AWG through 1 AWG.
110.14(C)(1)(b) applies because the termination provisions are marked for conductors larger than 1 AWG.

Please help me understand how the code handles this. Thanks in advance.

 

[oldsparky52]

I'm not sure, but I believe it's the equipment not the lugs that are the determining factor.

 

[charlie b]

I agreed. Whether the lugs are "marked" or "listed" for specific wire sizes is not the sole deciding factor. You also need to know the insulation temperature rating (60, 75, or 90C) and the temperature rating(s) of the lugs or any other device to which the conductors are connected. If for example you connect #8 THHN conductors (insulation rating 90C) to lugs that are rated 75C, with the same type lugs at each end of the conductor, then you can use the 75C table to find the ampacity of the conductors.

 

[jim dungar]

As the others have said, the NEC rules are about the entire termination, not just the lugs.

For several decades now, most protective devices have been dual rated 65/75, which is may be how they span the two code sections.

 

[xptpcrewx]

Thanks every one, this makes sense overall.... however, please consider the following situation:

Assume I am now dealing with a piece of equipment rated 125A, with aluminum load lugs "marked" but not necessarily "listed" for use with 12 AWG through 3/0 AWG conductors... I will use a 1 AWG conductor with THHN wire.

When applying 110.14(C)(1), what is the limiting temperature rating that should be used? (60 or 75 deg C?)

 

[david luchini]

Thanks every one, this makes sense overall.... however, please consider the following situation:

Assume I am now dealing with a piece of equipment rated 125A, with aluminum load lugs "marked" but not necessarily "listed" for use with 12 AWG through 3/0 AWG conductors... I will use a 1 AWG conductor with THHN wire.

When applying 110.14(C)(1), what is the limiting temperature rating that should be used? (60 or 75 deg C?)

75 deg C

 

[infinity]

Thanks every one, this makes sense overall.... however, please consider the following situation:

Assume I am now dealing with a piece of equipment rated 125A, with aluminum load lugs "marked" but not necessarily "listed" for use with 12 AWG through 3/0 AWG conductors... I will use a 1 AWG conductor with THHN wire.

When applying 110.14(C)(1), what is the limiting temperature rating that should be used? (60 or 75 deg C?)

As David stated 75° C. What does the bold mean?

 

[Carultch]

When applying 110.14(C)(1), what is the limiting temperature rating that should be used? (60 or 75 deg C?)

Most equipment is 75C. For equipment over 100A that doesn't specify, the NEC specifies that the 75C rating is the default. The equipment would have to have specific instructions otherwise, if it required you to use sizing from the 60C column for its terminations, or allowed you to use the 90C rating. It is rare that you get to use the 90C rating when terminating in equipment. The value of having wire with a 90C rating, usually manifests when it gives you an extra margin to make your calculations for ambient temperature and bundling adjustment factors.

For equipment that is 100A and less, you have the burden of proof if you intend to take credit for the 75C rating. Otherwise, 60C is the NEC's default rating for equipment in this size. This is more of an academic rule than a practical rule, because most products today are listed otherwise for either 60C/75C dual or 75C straight. It will apply when taking an exam, but you'll rarely have a realistic example in practice where it matters. So you'd need to either look for a general statement at the front of the exam specifying it, or a statement in each problem. And if it is unspecified, you'd need to assume 60C.

The meaning of the dual rating 60/75C rating, is that it allows you to use a 60C rated wire with 60C sizing, and it allows you to use 75C or 90C wire with 75C sizing. If it were straight rated for only 75C, you'd have to use wire rated 75C or higher. Even with 60C sizing, you couldn't use TW or UF wire, that carries a 60C rating.

 

[xptpcrewx]

75 deg C

Hi David,

Could you explain your reasoning? 110.14(C)(1)(a) and 110.14(C)(1)(b) can both apply as I read it. Thanks in advance,

 

[xptpcrewx]

As David stated 75° C. What does the bold mean?

The bold means that the equipment is not listed and is marked for 12 AWG through 3/0 AWG....
This was specifically mentioned to clarify that Table 310.15(B)(16) would not apply here because the statement "Unless the equipment is listed and marked otherwise....." is not true. Therefore, we must default to 110.14(C)(1)(a) and 110.14(C)(1)(b) and not Table 310.15(B)(16),

 

[xptpcrewx]

Most equipment is 75C. For equipment over 100A that doesn't specify, the NEC specifies that the 75C rating is the default. The equipment would have to have specific instructions otherwise, if it required you to use sizing from the 60C column for its terminations, or allowed you to use the 90C rating. It is rare that you get to use the 90C rating when terminating in equipment. The value of having wire with a 90C rating, usually manifests when it gives you an extra margin to make your calculations for ambient temperature and bundling adjustment factors.

For equipment that is 100A and less, you have the burden of proof if you intend to take credit for the 75C rating. Otherwise, 60C is the NEC's default rating for equipment in this size. This is more of an academic rule than a practical rule, because most products today are listed otherwise for either 60C/75C dual or 75C straight. It will apply when taking an exam, but you'll rarely have a realistic example in practice where it matters. So you'd need to either look for a general statement at the front of the exam specifying it, or a statement in each problem. And if it is unspecified, you'd need to assume 60C.

Carultch, Thanks for the reply. While I think your statements are generally correct as it relates to equipment ratings either ≤ 100A or >100A, one thing that seems to be bug me is that you left out the part having to do with conductor ranges. 110.14(C)(1)(a) and 110.14(C)(1)(b) both have or statements. This is the reason I presented the second example, because the or statements have a case where 110.14(C)(1)(a) and 110.14(C)(1)(b) can both apply to the same situation. Thanks

 

[Carultch]

Carultch, Thanks for the reply. While I think your statements are generally correct as it relates to equipment ratings either ≤ 100A or >100A, one thing that seems to be bug me is that you left out the part having to do with conductor ranges. 110.14(C)(1)(a) and 110.14(C)(1)(b) both have or statements. This is the reason I presented the second example, because the or statements have a case where 110.14(C)(1)(a) and 110.14(C)(1)(b) can both apply to the same situation. Thanks

Good catch. So the cutoff isn't just "100A and less, vs over 100A", but it would also have to be marked for #1/0 or larger to have it follow the rule for "over 100A" and be 75C rated without specific documentation. From what I've seen in practice, most 100A devices allow at least 1/0, and I've never seen device over 100A with a maximum size of #1.

If you look thru the 60C copper column, you'll notice that the only possible sized device that could fit in this overlap, is a 110A device, which has #1 terminals and no provisions for anything larger to be connected. The only size you could connect, would be #1 Cu. Using #2 Cu would require a 75C equipment rating, and #1/0 wouldn't fit. A 125A device would either have to have 1/0 terminals if it specifically required using the 60C rating, or it would have to have a 75C rating to use anything smaller.

This piece of equipment is so hypothetical, I don't think it would've ever existed. It is common for terminals to have a margin of design flexibility, and allow a couple sizes larger than the absolute minimum. Plus, in an effort to standardize on components, manufacturers often group a range of sizes in the same overall design. If a manufacturer makes a 110A, 125A, and 150A breaker, that manufacturer will likely use the same housing, the same physical size, and the same terminals for all 3 models. The essential difference would be the calibration of the trip mechanism.

 

[david luchini]

Hi David,

Could you explain your reasoning? 110.14(C)(1)(a) and 110.14(C)(1)(b) can both apply as I read it. Thanks in advance,

I don't see how 110.14(C)(1)(a) would apply. You have equipment that is rated over 100A and you have a termination marked for conductors larger than #1 AWG.

 

[david luchini]

This was specifically mentioned to clarify that Table 310.15(B)(16) would not apply here because the statement "Unless the equipment is listed and marked otherwise....." is not true.

You've lost me here. The provision you reference says that T310.15(B)(16) DOES apply to determining the rating of the termination.

 

[xptpcrewx]

I don't see how 110.14(C)(1)(a) would apply. You have equipment that is rated over 100A and you have a termination marked for conductors larger than #1 AWG.

But the termination is also marked for conductors less than 1 AWG.

You've lost me here. The provision you reference says that T310.15(B)(16) DOES apply to determining the rating of the termination.

Your are correct!

I need to modify my statement above to:

Table 310.15(B)(16) applies here because the statement "Unless the equipment is listed and marked otherwise....." is not true. Therefore, we must use Table 310.15(B)(16)(B) in addition to 110.14(C)(1)(a) and 110.14(C)(1)(b).

I think Carultch hit the nail on the head with the example... I will need to pick a size wire and then apply all rules for the conflicting case. The mistake is applying 110.14(C)(1)(a) and 110.14(C)(1)(b) alone.

If anyone is wondering/questioning the practicality of this example, it is something dealt with frequently by power system engineers when modeling Short-Circuit, Coordination and Arc-Flash Hazard studies...

For power system modeling (new construction) only equipment specifications listed in the proposed bill of materials are provided. We must model wire sizes and insulation type based on this information and it can become a challenge to determine the temperature rating that conductors must be limited to. We are often given ranges for termination provisions. Also said equipment may have adjustable OCPD settings that will be determined later in the Coordination study, so the rating could very well change to above or below 100A in some cases...

Why model insulation type at the Short-Circuit study stage? because the next step in the power system study is Coordination and we need minimum and maximum allowable ranges for setting each OCPD. This of course is limited to many factors, one of which is the conductor ampacity based on the temperature rating of 110.14(C)(1)(a) and 110.14(C)(1)(a) (which basically translates to insulation type/rating)

 

[david luchini]

But the termination is also marked for conductors less than 1 AWG.

#3/0 is larger than #1. 125A is greater than 100A.

You need to use 75C conductors, or 90C conductors at the 75C ampacity.

Your are correct!

I need to modify my statement above to:

Table 310.15(B)(16) applies here because the statement "Unless the equipment is listed and marked otherwise....." is not true. Therefore, we must use Table 310.15(B)(16)(B) in addition to 110.14(C)(1)(a) and 110.14(C)(1)(b).

I think Carultch hit the nail on the head with the example... I will need to pick a size wire and then apply all rules for the conflicting case. The mistake is applying 110.14(C)(1)(a) and 110.14(C)(1)(b) alone.

I'm still not sure what you are getting at. If you are concerned about modeling the conductor insulation in your power system studies, use the 75C insulation rating. If you have a 75C rated piece of equipment and you need to set the OCPD to 80A, you still have a 75C rated piece of equipment.

 

[xptpcrewx]

I'm still not sure what you are getting at. If you are concerned about modeling the conductor insulation in your power system studies, use the 75C insulation rating.

Are you suggesting all equipment/devices will always be 75C in a power system?
The whole point is to know which wires are limited to 60C ampacities when setting OCPD's. Making all insulation 75C does not help.

Just to clarify entering 60C insulation into the model does not mean that is the insulation type used in the field, its just a way to model 60C ampacities.

If you have a 75C rated piece of equipment and you need to set the OCPD to 80A, you still have a 75C rated piece of equipment.

Yes, but the reason I may have to set the OCPD at 80A could be because the ampacity of the 75C conductor needs to be limited to 60C.

110.14(C)(1) is about matching terminal provisions to the wire temperature ratings, but because we already know the terminal provisions in my example(s), we are essentially working the problem backwards to verify compatibility.

If the OCPD is now rated 80A (240.6(C)) aren't we limited to 60C ampacity as per 110.14(C)(1)(a)?