MattWilliams
Member
- Location
- Minnesota
- Occupation
- Instructor
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?
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?
