Equipment vs Lug Temp Ratings

[Alwayslearningelec]

Been watching MH calculation videos. he mentions that lugs may very well be rated for 90 degree but the equipment may be 75 degree.

Is that true? is there a separate rating for the equipment? Where is that listed? Thanks

 

[Elect117]

UL White book.

Now UL Prospector

Product code AALZ.

They don't test equipment for ampacity (heat) above 75°C. This is a common mistake among engineers and contractors. More often an issue for engineers since they don't see product labels in the field that often. If you have the handbook or NFPA link, they explain it the best. IT is in section 110.14(C).

For example, you will most likely never find a panelboard rated 90°C. The rating is printed on the label sticker. It is not always easy to find and the print is small. So people hardly read it. Most are rated 75°C, though I imagine the old ones rated less 100A, and not labeled with a temperature would need to be assumed as 60°C.

Breakers are another thing that are rarely rated for more than 75°C. I think recently there was something made for solar that had a 90°C rating but I am not sure.

The most common use for using the 90°C wire is for derating or where you have a long run on cable tray and you splice from like 10 parallel sets at the gear to 6 parallel sets and then back to 10.

 

[ron]

I have not seen equipment listed/rated at 90deg (although the lugs in isolation might be), so the assembly gets is feeders sized at 75 deg (or 60 deg depending on the application)

 

[infinity]

I have not seen equipment listed/rated at 90deg (although the lugs in isolation might be), so the assembly gets is feeders sized at 75 deg (or 60 deg depending on the application)

Yes 75° C is de rigueur for modern equipment. Unless you're dealing with a test question 75° C is probably applicable 99.9% of the time.

 

[jim dungar]

Yes 75° C is de rigueur for modern equipment. Unless you're dealing with a test question 75° C is probably applicable 99.9% of the time.

And has been for more than 40 years now.

 

[Alwayslearningelec]

Thanks. have a feeling in time equipment may begin to get tested/rating at 90 degree,

 

[Elect117]

UL Product IQ *** not prospector. sorry.

 

[jim dungar]

Thanks. have a feeling in time equipment may begin to get tested/rating at 90 degree,

Not likely. We have had 90°C wiring , like THHN, for 50 years, which is almost longer than 60°C insulation was the standard.

 

[don_resqcapt19]

The equipment manufacturers often use lugs purchased from other manufacturers and those lugs often have a 90℃ or even 105℃ rating, but the equipment rating would be 75℃.

 

[Alwayslearningelec]

I don't get the concept of equipment rating. What does that exactly mean? I understand lugs being rated for certain temp but say the enclosure of panelboard or whatever they would mean by "equipment" when referring to a panel.

 

[Elect117]

I don't get the concept of equipment rating. What does that exactly mean? I understand lugs being rated for certain temp but say the enclosure of panelboard or whatever they would mean by "equipment" when referring to a panel.

How do you rate the busbar in a panelboard? How would you rate the enclosure that busbar is in? How thin can the enclosure be? What material can that enclosure be made out of?

All of that would need to be tested so that when someone wants to install a panelboard they know that the enclosure is suitable for the busbar and the connections being made within it.

Lets say they say their panelboard is rated for 200A. How do they test that it can handle that? They need to set limits to the temperature and environment and then test it won't melt or fail.

 

[don_resqcapt19]

I don't get the concept of equipment rating. What does that exactly mean? I understand lugs being rated for certain temp but say the enclosure of panelboard or whatever they would mean by "equipment" when referring to a panel.

It is the equipment that the lugs are physically connected to. For example thermal magnetic breakers could easily trip below their nameplate rating of you connected 90 degree conductors running at the 90 degree ampacity to the breaker lugs even though the lugs themselves are rated for 90C.

It would not be the enclosure itself, however that does contribute to the heat at a breaker, and is the real reason you need a breaker to be sized at 125% of the continuous load, given that the breaker testing standard requires a breaker to carry its rated load forever with a single breaker in a 40 degree C ambient.

 

[Carultch]

I don't get the concept of equipment rating. What does that exactly mean? I understand lugs being rated for certain temp but say the enclosure of panelboard or whatever they would mean by "equipment" when referring to a panel.

It's not necessarily that any piece of material in the equipment necessarily reaches a temperature of 75C. The wire ampacity table is based on the conductor carrying its full load in (usually) 30C air, and staying within safe margins of the temperature rating (60C, 75C, or 90C), so it doesn't damage the insulation. The 110.14(C) termination rules use the framework of the conductor ampacity table, but with other factors being tested, than just exceeding a temperature.

From what I understand about the testing, they connect the equipment with 75C sized wiring to its test source/load, provide a background temperature of (usually) 40C, and test that it can safely operate at those conditions. For instance, 300A equipment, would be tested at its full rating with 350 kcmil Cu wiring and 500 kcmil AL wiring, to confirm that neither causes problems for the equipment. This confirms a 75C termination rating. For a 90C termination rating, they'd need to test it with 300 kcmil Cu and 400 kcmil AL wiring, and have it pass the same tests.

It's very common that the lug itself is rated for 90C, but the equipment is limited to 75C, or much less common, 60C. It's a special case that you get to take credit for the lug's 90C rating. Such as if it's part of 90C rated equipment, or if it's separately-installed in an empty enclosure.