More Than One Neutral Under
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
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.
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.
Technical Editorial Director
Mike Holt Enterprises
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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.