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More Than One Neutral Under a Terminal

Mike,
I am an Oklahoma housing inspector and I find that often find panels wired with two neutral conductors under the same terminal. I find this type wiring everywhere and believe it is wrong based on figure 408.15 of your book page 372 "Understanding the National Electric Code.

When I write them up as having multiple neutrals under the same lug and grounds and neutrals mixed, an electrician comes behind me and says that there is nothing wrong. Note: These panels are mains not sub panels.

Hi Fred,
You are correct; the 2002 NEC does not allow multiple neutrals under the same lug. In the previous code, it was not specifically mentioned, although it was a UL listing requirement and all wiring must be in accordance with listing instructions [110.3(B)].

110.14(A) states "Terminals for more than one conductor shall be so identified." When looking at the manufacturer's label inside the panel, you may see it lists 2 or 3 conductors per terminal for the equipment ground, but it does not list multiple conductors for the neutral. Section 408.21 in the 2002 NEC specifically states, "Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor."

The one neutral per terminal has been a UL requirement, but has not always been enforced by all electrical inspectors. Consequently, many electricians will not recognize this as an unacceptable practice until their local inspectors enforce it. This may take time to change in some areas- and even at that, it will take effect on new installations but not necessarily require existing installations to be updated. This is something that is under the control of the local inspection authority and 90.4 gives the AHJ a lot of discretion.

Your role as an inspector may well be to help educate the electricians. In order to do that, your need to take a tone of explaining why the multiple neutrals are a poor idea. Read and make sure you fully understand the theory explanation on page 372 of Understanding the NEC in regard to lost neutral connections.

Steve Arne
Technical Editorial Director
Mike Holt Enterprises
arne@mikeholt.com

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Understanding the NEC, Volume 1 Book — 2002

Understanding the NEC Volume 1 was written to provide insight into, and an understanding of, many of the technical rules of the NEC. This book, printed in four color, contains clear graphics, examples, and 1200+ summary questions. Based on the 2002 NEC.

Product Code: 02UND1
ISBN: 0-9710307-1-5
Pages: 430
Illustrations: 830

Table of Contents
Sample Pages
Sample Graphic

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