UL Errata

Status
Not open for further replies.
C

chrisplusian

Member
Location
Orange Park, FL
Occupation
Automation Systems Engineer
Does anyone know if Underwriters laboratories lists errata anywhere? I have a manufacturer who is siting UL 1996 when saying conductors under 100A are supposed to be sized based on the 75 degree column, and I pointed him to 110.14. Oddly enough he shared the section from UL 1996 (2016 edition) which says the following:

25. TEMPERATURE RATING OF FIELD INSTALLED WIRING For some equipment, the testing and construction are based on the use of wiring with 75°C insulation. However, most equipment, where ampacities of 100 or less are involved, is marked for use with 75°C rated conductors at 75°C ampacities. The use of wiring with 75°C insulation is necessary when conductor ampacities higher than 100 are required. When the use of wiring with insulation rated higher than 75°C (or 75°C) is required because of terminal or wiring compartment temperatures, the equipment must be marked to specify the minimum temperature rating (90°C) and the minimum conductor size of the wires unless the conductor size is to be based on the 75°C wire ampacity. Such markings are located adjacent to the field-wiring connection point or on an attached wiring diagram and are visible while making the connections and after they have been made. Some equipment is marked to indicate an area for locating field wiring and splices to prevent excessive insulation temperatures.


It could be I am misunderstanding the intent of this, but it seems like they should have put 60C in a place where they have 75C. I wanted to check if this was errata, or potentially contact them for a better understanding of the intent. I don't know that they have a "contact" per say, but I thought I would ask here first. Thanks in advance.
 
Which number do you believe is incorrect, is the one in bold? Does it change anything?

25. TEMPERATURE RATING OF FIELD INSTALLED WIRING
For some equipment, the testing and construction are based on the use of wiring with 75°C insulation. However, most equipment, where ampacities of 100 or less are involved, is marked for use with 75°C rated conductors at 75°C ampacities. The use of wiring with 75°C insulation is necessary when conductor ampacities higher than 100 are required. When the use of wiring with insulation rated higher than 75°C (or 75°C) is required because of terminal or wiring compartment temperatures, the equipment must be marked to specify the minimum temperature rating (90°C) and the minimum conductor size of the wires unless the conductor size is to be based on the 75°C wire ampacity. Such markings are located adjacent to the field-wiring connection point or on an attached wiring diagram and are visible while making the connections and after they have been made. Some equipment is marked to indicate an area for locating field wiring and splices to prevent excessive insulation temperatures.
Click to expand...
 
Sorry, I could be wrong but I see nothing incongruent between the UL section quoted and the NEC section you reference.
 
You are looking for correlation to what UL 1996 says about the INTERNAL requirements for wiring in heaters, to what the NEC says about terminations in the FIELD. They are not related. Their responsibility to meet UL 1996 wiring requirements stops at the terminals, your responsibility to properly terminate begins there but does not progress backward into their equipment. In other words YOU as the installing electrician don't need to be concerned with what they did inside of their listed equipment.
 
Please forgive me for the wall of text I am about to post. In order to clear my confusion I am going to go through the UL statement line by line:

For some equipment, the testing and construction are based on the use of wiring with 75°C insulation.
I am ok with this statement. Just as a great deal of instrumentation is only tested with class 2 power supplies, and are only listed for use with such. In that case it is the manufacturers responsibility to say a class 2 power supply is required to power the instrument. However this line says "some equipment" and does not say that 75C insulation is a requirement of the test.

However, most equipment, where ampacities of 100 or less are involved, is marked for use with 75°C rated conductors at 75°C ampacities.
My biggest problem is with this statement. I am not sure how to read this. UL typically considers NFPA 70, NFPA 77, NFPA 780, and other relevant codes and standards as applicable. They do not in general make listings in deviation unless there is a good reason to do so. The NEC 110.14 says termination previsions for equipment 100 amp or less or marked for 14AWG-1AWG shall only be used for only 60C conductors or conductors with a higher temperature rating provided the 60C ampacity column is used. 110.14 (C) opens with a statement saying conductor sizes shall be selected and coordinated so as not to exceed the lowest temperature rating of any termination, conductor, or device. I was honestly wondering if this section of the UL comment should not have said "However, most equipment, where ampacities of 100 or less are involved, is marked for use with 75C rated conductors at 60C ampacities". If the intent of what UL has is in fact to say that they are using 75C ampacities, that means the entire circuit from the equipment to the branch circuit overcurrent/short circuit device has to be 75C rated to be compliant. This adds significant costs in some situations to accommodate a piece of equipment which costs a fraction of the cost difference to go to 75C.

The use of wiring with 75°C insulation is necessary when conductor ampacities higher than 100 are required.
This too seems to line up with NEC 110.14. My question is why would you make a mark of deliniation at 100 amps unless to signify something is different? In one case they say less than 100 amps is typically 75C and above 100 amps is 75C. Something just seems off here and that's what makes me think the intent was to parallel what the code says: you can use higher rated conductors as long as you follow the 60C ampacities.

When the use of wiring with insulation rated higher than 75°C (or 75°C) is required because of terminal or wiring compartment temperatures, the equipment must be marked to specify the minimum temperature rating (90°C) and the minimum conductor size of the wires unless the conductor size is to be based on the 75°C wire ampacity.
I can't even begin to understand what or why they are saying this. Before going to college when I worked as an electrician (somewhere in the early and mid 2000's) I had to install a few heat lamps for commercial food applications. I had to use some crazy wire that was rated for an extreme amount of temperature, and because it was installed within inches of a heat lamp that glows red to keep food hot we were only allowed to load the conductors to less than half of what the conductors were rated for. I am not sure why that was, but I recall being told since they were already subjected to extreme heat they could not handle the thermal rise of the fixtures.

To summarize, why would UL REQUIRE that conductors be sized based on larger ampacities, in a piece of equipment that will have high temperatures? It seems the opposite of intuitive. It makes sense to require the higher temperature insulation rating, but not to suggest or require you to use the higher ampacities of the 75C column. I am being told by the equipment manufacturer that the listing requires the use of 75C column. I do not see that in the statement UL provided, but I see something that seemed a bit off and wanted to know if there is a way to check errata (like with NFPA they publish corrections). Or potentially touch base with someone regarding the listing so I can understand it better. I was hoping someone here may have had to deal with something similar and might be able to short cut my path.
 
@Jraef I agree with your statement, with the one exception. As an installer or someone who designs the electrical system, it is my job to coordinate circuits and their connections. So if someone said they had a piece of equipment "Listed" for a particular application and things don't line up I do have to question it. A previous example: a well known VFD manufacturer provided me a cut sheet for an enclosed VFD which was listed for use with #10 THWN. The entire assembly was UL 508 listed. The cut sheet warned that ambient temperatures inside the enclosure would reach 110-115F. They suggested not to install the enclosure in such a way as to prevent the surfaces from being able to dissipate heat as a result. You will never guess what the AHJ pointed out during permit. If the conductors are run from the field they fall under NEC rules, since the conductors are subjected to a higher ambient in the enclosure (which was only a chase nipple away from the panel that fed it) the conductors had to be de-rated. For THWN it means we can use the 75C column to derate, but correction factor for that ambient was I think .80 or .82? In any case the conductor had to be the next size to accommodate and then no longer fit the listing requirements. There are ways around that with reducing crimp connectors, which is what the AHJ allowed us to do, but my point is a UL listing is not a pass on the rest of the installation. And in this case the listing allowed ambient temperatures that meant de-rating was required, but their terminals were not listed for larger wires. Kind of doesn't make sense, but we are all human and sometimes mistakes are made. My real question here is if there is truly a mistake or if I just can't see the forest for the trees.
 
What about 310.15(A)(2)

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be used.
Exception: Where different ampacities apply to portions of a circuit, the
higher ampacity shall be permitted to be used if the total portion(s) of
the circuit with lower ampacity does not exceed the lesser of 3.0 m
(10 ft) or 10 percent of the total circuit.
Informational Note: See 110.14(C) for
conductor temperature
limitations due to termination provisions.
Click to expand...
 
@Dennis Alwon I can see the line of reasoning, but unfortunately I am not an expert in thermal dynamics. The bulk of my understanding is from the apprenticeship program as a young electrician, and continuing education now in the world of engineering. The requirements of 110.14 apply to temperature limitations of terminations, while 310.15 applies to ampacity. By definition ampacity applies to the current a conductor can carry without exceeding its temperature limitations. This doesn't consider the amperage a terminal can handle without exceeding its temperature limitations.

When I was taught the concept of 110.14(C) I was told to picture the conductor as a heat sink for the terminals. If a terminal is rated 60C it can only handle the thermal rise of a load as listed in the 60C column. That isn't to say the conductor cannot handle more. If the conductor is loaded to the 75C column the terminal does not get to sink adequate thermal energy to the conductor, because of the temperature rise associated with the higher load. As a result (years down the road) you may see carbon tracking on the device the terminal is attached to (circuit breaker, contactor, etc), and you may see the same occur on the conductor (sometimes nearest the terminal since the terminal will slightly overheat, and sometimes at other places where ambients reach temperatures above anticipated, etc). For this reason the ENTIRE circuit needed to be treated as 60C if ANYTHING was 60C because thermal energy can propagate, with time, through the majority of the circuit.

I believe the 2020 NEC does a great job of clearing this up. They completely changed the section you mentioned. 310.15(A) now reads:


Ampacities for conductors rated 0 volts to 2000 volts shall be as specified in the Ampacity Table 310.16 through Table 310.21, as
modified by 310.15(A) through (F) and 310.12. Under engineering supervision, ampacities of sizes not shown in ampacity tables for
conductors meeting the general wiring requirements shall be permitted to be determined by interpolation of the adjacent conductors
based on the conductor’s area.
The temperature correction and adjustment factors shall be permitted to be applied to the ampacity for the temperature rating of the
conductor, if the corrected and adjusted ampacity does not exceed the ampacity for the temperature rating of the termination in
accordance with the provisions of 110.14(C).
Informational Note No. 1: Table 310.16 through Table 310.19 are application tables for use in determining conductor sizes on loads
calculated in accordance with Part II, Part III, Part IV, or Part V of Article 220. Ampacities result from consideration of one or more of the
following:
(1) Temperature compatibility with connected equipment, especially the connection points.
(2) Coordination with circuit and system overcurrent protection.
(3) Compliance with the requirements of product listings or certifications. See 110.3(B).
(4) Preservation of the safety benefits of established industry practices and standardized procedures.
 
@chrisplusian

Actual the wording is the same they just changed the section number

310.14(A)(2) Selection of Ampacity.

Where more than one ampacity applies for a given circuit length, the lowest value shall be used.
Exception:
Where different ampacities apply to portions of a circuit, the higher ampacity shall be permitted to be used if the total portion(s) of the circuit with lower ampacity does not exceed the lesser of 3.0 m (10 ft) or 10 percent of the total circuit.
Click to expand...
 
@Dennis Alwon
I see it now. You are right it hasn't changed, just a new location. I am still under the impression (based on 310.14(A)(2) this section considers the wire and not the terminal considerations. The informational note of 310.14(A)(2) seems to point that direction too, but I am not closed to the idea that I am missing something.
 
chrisplusian said:
@Dennis Alwon
I see it now. You are right it hasn't changed, just a new location. I am still under the impression (based on 310.14(A)(2) this section considers the wire and not the terminal considerations. The informational note of 310.14(A)(2) seems to point that direction too, but I am not closed to the idea that I am missing something.
Click to expand...
310.14(C) in the 2017 and it appears the same in the 2020

(C) Temperature Limitations. 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. Conductors
with temperature ratings higher than specified for terminations
shall be permitted to be used for ampacity adjustment,
correction, or both.
Click to expand...
 
Status
Not open for further replies.
Top