What is in this article?:
- What's Wrong Here?
- Find the Answer
Hint: As the main bonding jumper (the green screw) in this load side subpanel shows, the ends don't always justify the means.
Find the Answer
Robert O'Brien, project manager, Riggs Distler & Co., Inc. of Sharon Hill, Pa., pointed out that if this is a subpanel, then the green bonding screw in the neutral bar violates 250.24(A)(1), which notes that the service must be grounded at an accessible location up to the bus where the neutral is connected. This subpanel is located well past that point. Also, 250.24(A)(5) prohibits the grounding of the grounded conductor on the load side of the service disconnect, except as otherwise allowed in this Article. The subpanel is located on the load side of the service disconnect. However, if this were a separately derived system and this were the ground connection to the secondary grounded conductor, then the separate equipment grounding terminal bar would be a violation.
James Williams, president, Ace Electric of Shelby, Kings Mountain, N.C., noted other violations. The equipment grounding conductor and the grounded conductor (neutral) must be separate from each other in a subpanel. Use of the green screw violates the requirements of 408.20. Verification of 300.4(F) must also be ensured for the insulated bushing for the chase nipple.
John McEldowney, regional electrical inspection supervisor, New Jersey Department of Transportation, Trenton, N.J., noted the neutral terminal bars, located on each side of the enclosure, should be electrically bonded. His concern arose when he saw more than two green equipment grounding conductors terminated under several of the terminal screws, which is a violation of 110.3(B).