I just looked up in our electrical buyers guide under lugs and it appears that they offer "All" lugs rated for 90 degrees. If this is so and all terminals are rated for 90 degrees than why cant I use the wire ampacity from the 90 degree column for my feeders?
Thanks.
In a general sense, you should plan on terminations for 75C, and if using 90C wire, you can use the 90C column for your ampacity bundling adjustment and temperature correction calculations. Termination ampacity requirements apply before you include derate calculations. Wire ampacity applies after bundling and temperature derate corrections. This is the most common reason why you would use the 90C column of the NEC.
It is rare that you are able to use the 90C column of the NEC for terminations. Both sides need to be listed and labeled for 90C.
While it may be very true and very common, that lugs appear to be listed and labeled for 90C, if the lugs are on manufactured product (switches, panelboards, breakers, etc), then it is very rare (if ever) that you will see the entire manufactured assembly listed and labeled for anything higher than 75C. It is only when you use separately installed connectors on both sides, that you can take credit for the connectors' 90C rating. Split bolts, splice reducers, insultaps, insulation piercing connectors. And it is best if these are in separate enclosures from any manufactured product.
Here is a white paper that describes this in more detail:
http://static.schneider-electric.us/docs/Power Management/0110DB9901.pdf