Code Question of the Day with Charlie Trout

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The National Electrical Code is the bedrock of the electrical construction business.

Do you know all the ins and outs of the Code? NECA and Electrical Contractor magazine are pleased to present their daily online feature, “Code Question of the Day.”

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Code Question Of The Day

Friday, October 01, 2010

Subject: Terminating Neutrals on Neutral Bus.

Hi, my question is regarding the neutral bus in a breaker panel. I've heard that 2 neutral conductors of the same gauge can be terminated under one screw as opposed to separating each one. I've also heard that they cannot be doubled up. I could not find an answer either way in the codebook. I frequently run into existing panels that may have additional breaker space free, but have no room for additional grounding conductors or grounded conductors. It's these times I'd like to know for sure whether to double up conductors or not and if opposing phases or like phases need to be considered.

Thanks for all the great info.
I look forward to the column each day!

Michael Janiszewski



Hey Michael, NEC 408.41 requires that each grounded conductor must terminate within the panelboard in an individual terminal that is not also used for another conductor. There is an exception for grounded conductors of circuits with parallel conductors but only if the terminal is identified for connection of more than one conductor. NEC 408.40 prohibits equipment grounding conductors from being connected to a terminal bar provided for grounded or neutral conductors unless the bar is identified for the purpose.


Section: 408..40, 408.41
Source: Charlie Trout

ABOUT CQD: NECA’s Code Question of the Day (CQD) is Charlie Trout’s flagship National Electrical Code® forum for NECA and the industry. The CQD continues to generate a lively dialogue and relative Code-based and practical responses to an ever-increasing and interactive audience.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, is a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training.

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