110.14.c

[wasasparky]

Can we assume standard breakers, panels and transformers can be wired as 75C connections?

Found some info on transformers, use 90C lugs, but probably not what the overall "rating" is?

 

[celtic]

Can we assume standard breakers, panels and transformers can be wired as 75C connections?

Found some info on transformers, use 90C lugs, but probably not what the overall "rating" is?

I would say it is "safe to assume" a 75?C rating - but it always best to "know" what you are dealing with...

Most terminations are normally designed for 60?C or 75?C maximum temperatures, although some are now being designed for 90?C. Therefore, the higher-rated ampacities for conductors of 90?C, 110?C, and so on, cannot be used unless the terminals at which the conductors terminate have comparable ratings.

Copied from 2002 NECH , commentary following 310.10.
​

...and that's not to say you shouldn't assume it's a 60?C termination.

 

[templdl]

The lugs may be rated 90degC but they most likely have been supplied by the transformer manufacturer which them means that the transformer is UL listed with the lugs. Then it becomes a matter of what temperature rise the luds on the transformers have been tested at. It's best to look at the manufacturer's instructions which should clarify how the cable should be applied which most likely is 75degC.

 

[jim dungar]

I know of no UL listed device (splicing items not included) that is suitable for use with conductors sized using the 90C column. Many devices might require 90C conductors but they must be sized using the 75C column.

It is way too common of a myth that changing a lug (which are almost always listed at 90C) changes the rating of the termination (which it doesn't).