Some questions concerning wire temperature ratings. Briefly, 100 amp service, and due to on going remodeling and ever changing plans, a service disconnect was placed within five feet of the meter, and the new load center several feet away, using EMT raceway.
Table 310.15(B)(6) indicates #4 copper for 100 amp residential, which was used between the disconnect and the load center. However, after reading Section 110 and referencing table 310.16, the wire ampacity is limited to the temperature rating of the equipment. The wire is #4 copper THWN-2/THHN 90degree Centigrade, and the equipment is conductor rated at 75 degree Centigrade. Per the table, this limits the ampacity to 85 amps at 75 degrees Cent.
Q- Is the #4 undersized based on the equipment temperature rating? Should I have used #3 copper? Does this make a difference in residential wiring as it is not exposed to industrial heat conditions? Also, I replaced all the aluminum wiring with copper, and all new cooper use only swithes & outlets. The branch wiring is all 90 degree C-again any problems with this? What temp. rating is normally used in residential wiring?
BTW, all the wire sold here, both Southwire and Cerro, no matter the gauge are all rated 90 degreesC, yet all of the equipment and breakers I see are rated 75 degreesC. I was told all “new” wire is rated 90 degreesC, or maybe that's all that is sold at the "improvement" stores.