Are continuous loads rated at 100% permitted on 90 deg. C. equipment terminals.

[MattWilliams]

In Mike Holts Illustrated guide to Electrical Exam Prep (based on 2020) Shows the following question on page 172.

What size XHHW copper conductor can be used to interconnect 90 deg C rated power distribution blocks protected by a 400A overcurrent device serving a 320A continuous load?

The answer is 400 kcmill rated at 380A at 90 deg. C. I agree with the wire size given will be protected by the 400 A breaker. The concern I have with this is they did not provide an increase in wire size for the continuous load. This appears to be justified by the statement in figure 6-14, which states "A 320A continuous load at 100% is permitted on 90 deg. C. equipment terminals. Where is that in the code book?

I understand equipment that is listed as a continuous load may be used at 100% instead of 125% ( 210.19(A)1(a) Exception 2 but where do we get the permission to use 90 degree rated equipment for less than 125% of continuous load?

 

[david luchini]

I understand equipment that is listed as a continuous load may be used at 100% instead of 125% ( 210.19(A)1(a) Exception 2 but where do we get the permission to use 90 degree rated equipment for less than 125% of continuous load?

The exception that you note covers this. Note that the exception refers to 110.14(C)(2).

 

[MattWilliams]

I just received the reference for 215.2(A)1(a) exception 2. Unfortunately, I didn't see this response until after I sent another e-mail. Please disregard the 2nd e-mail. That summarizes what I was looking for. It's all about exception 2.

Thanks Again Dave,
You have been a big help

 

[Rock86]

How many utilize this exception? Is it actually cost effective to this?