Mike Dolt Enterprises
Mike Dolt Enterprises
User: Guyute, Location: Ft Collins, CO
Asked on: Wednesday, April 13, 2011 at 8:50 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:10 am EDT
Question: If you size the equipment bonding jumper from 250.66 at the main disconnect. At what point do you start using 250.122 to size the EBJ. I have a ct can>400a disco>ATS>400a em disco and MCC respectively.
According to NEC 250.122(C), the equipment bonding jumper (EBJ) must be sized in accordance with 250.66, except as permitted in 250.122(C)(1), (C)(2), and (C)(3).250.122(C)(1)
If the equipment grounding conductor (EGC) is sized in accordance with 250.122(B) (i.e., the same size as the line conductors) and the EBJ is connected to the EGC, the EBJ must be sized in accordance with 250.122(B).
250.122(C)(2)
If the EGC is sized in accordance with 250.102(C)(1) (i.e., based on the rating of the circuit supplying the equipment) and the EBJ is connected to the EGC, the EBJ must be sized in accordance with 250.102(C)(1).
250.122(C)(3)
If the EBJ is connected to the grounded service conductor at the service entrance, the EBJ must be sized in accordance with 250.24(C).In your case, the equipment bonding jumper is connected to the main disconnect at the service entrance. Therefore, the EBJ must be sized in accordance with
250.24(C), which requires the EBJ to be sized based on the rating of the service-entrance conductors.Since the rating of the main disconnect is greater than 400 amperes, 250.66 would require an EBJ sized at 300 kcmil copper or 350 kcmil aluminum. Flag for review