20 ELECTRICALCONTRACTOR | OCT. 14 | WWW.ECMAG.COM
argue with the inspector. I have never
seen this before. Does the NEC require
those holes be covered?
No, the NEC does not mandate closing
holes for support that are not used. However, the general rule in Section 110. 12(A)
requires unused openings to be closed.
This is directed toward unused openings
for cables or conduits. The requirement
clearly states holes intended for the operation of the equipment, those intended for
mounting purposes, or those permitted as
part of a listed design are not required to
be closed. A panelboard cabinet or switch
enclosure may have holes designed for
mounting that are not used. The NEC
does not require them to be closed. While
it may be easier to appease the inspector
when you believe he or she is incorrect,
it is always advisable to engage in discussion. Ask them to help you understand by
showing you the applicable requirement
in the NEC.
In an older, 21-story commercial
building, we are replacing very old
panelboards as part of a complete
renovation of the tenant floors. The
panelboards are of different ratings but
all fed with feeder-tap conductors. The
feeders are fed from circuit breakers in
the gear room and are rated 200 through
600 amperes (A). The length of each
set of taps is, in almost all cases, less
than 10 feet, with none over 20 feet.
The drawings require the correct size
ungrounded conductors in accordance
with the 10- and 25-foot feeder-tap
rules in Section 240.21. The problem
is that the equipment grounding
conductors (EGCs) are sized based on the
overcurrent protective device (OCPD)
that the feeder taps terminate in and
not on the size of the OCPD protecting
the feeder. We brought this up to the
general contractor and received a letter
from an electrical engineer stating that
he did some calculations and the EGCs
as required were fine. We disagree. What
should we do?
You are correct. Section 250.122(G)
requires an EGC run with feeder-tap
conductors to be sized not smaller
than that required for the rating of the
feeder OCPD. This requirement does
not include permissive text to allow an
engineering evaluation to determine
minimum size. The OCPD in which
the feeder taps terminate provides
overload protection for the tap conductors only, and the OCPD protecting the
feeder protects the tap conductors in a
short-circuit or ground-fault situation.
The EGC installed with the feeder taps
must be sized to handle the fault current supplied through the feeder OCPD
and provide a low impedance path to
facilitate the operation of the OCPD.
The engineer must discuss this with the
electrical inspector. Section 90. 4 allows
the inspector to waive specific require-
ments where equivalent objectives are
achieved for safety. This would have to
be in writing from the inspector and is
very unlikely for several reasons. There
are just too many variables including, but
not limited to, the value of available fault
current used, the type of circuit breakers
protecting the feeders, and the mainte-
nance and history of the circuit breakers.
The future of the installation and pos-
sible replacement of the feeder OCPDs
must also be considered.
Splice in a panelboard?
The same argument comes up on many
jobs when a pull ends up a little short and
the conductors will not reach the neutral
bus or circuit breaker. Is it permissible to
splice in a panelboard?
The answer to your question begins with
the definition of “panelboard” in Article
100. A panelboard is typically made up
of bus and OCPDs; it is designed to be
installed in a cabinet or cutout box and is
only accessible from the front. The splices
you mention are not made in the panelboard. They are in the cabinet or cutout
box. Section 312.8 permits splices in
enclosures that contain OCPDs, provided
the maximum conductor fill provided is
DOLLARD is the safety coordinator for IBEW Local No. 98 in Philadelphia and works closely
with contractors to ensure job-site safety and compliance with all installation codes and standards.
He is a member of the NEC Correlating Committee, NEC CMP- 10, NEC CMP- 13, NFPA 70E,
NFPA 90A/B and the UL Electrical Council. He can be reached at firstname.lastname@example.org.
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