National Electrical Installation Standards

Standards as High as Your Own

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Thursday, May 26, 2022

Question:

Hello Code Question.

Recently, a 200 amp service upgrade has taken place at a residence. The grounding electrode conductors are too short to reach the neutral bar but will make it to a listed and labeled auxiliary ground bar. The ground bar has been installed per the panel manufacturer’s installation instructions using the supplied hardware. The electrical contractor has connected a properly sized bonding jumper, in this case, #4 CU, from the neutral bar to the properly installed auxiliary ground bar. The green main bonding jumper screw is still in place. This creates a redundant main bonding jumper. Given this situation, is it permissible to connect Grounding Electrode Conductors to the auxiliary ground bar? Should the green screw remain in place, or should it be removed?

Al Daniels

A

Answer:

Hi Al,

Thanks for the question. Based on the question, we believe you mean equipment grounding conductors (EGC), and based on your information it would be better to use the green screw as the main bonding jumper (MBJ) because that is how the equipment is listed. The wire-type MBJ is not necessary if the screw-type MBJ is installed and connects the neutral bus of the equipment to the metal panelboard enclosure. Follow the installation instructions and diagram on the equipment. See also Section 250.24(A)(4) for these types of connections.

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