Theatre Design & Technology - Summer 2013 - 22

QUICK REFERENCE CARD: NEC TERMINOLOGY
TERM
DEFINITION
Mandatory Rules, Article 90.5(A): "...actions that are specifically required or prohibited and are characterized by the use of
the terms shall or shall not."
Permissive Rules, Article 90.5(B): "...actions that are allowed but not required are normally used to describe options or
alternative methods, and are characterized by the use of the terms shall be permitted or shall not
be required"
Authority Having Jurisdiction, Article 100.1(AHJ): "An organization, office, or individual responsible for enforcing the
requirements of a code or standard, or for approving equipment, materials, an installation or a
procedure."
Effective Ground-Fault Current Path, Article 250.4(A)(5): "Electrical equipment and wiring and other electrically conductive
material likely to become energized shall be installed in a manner that creates a low-impedance
circuit facilitating the operation of the overcurrent device... It shall be capable of safely carrying
the maximum ground-fault current likely to be imposed on it from any point on the wiring system
where a ground fault may occur to the electrical supply source. The earth shall not be considered
as an effective ground-fault current path."
Equipment, Article 100.1: "A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the
like used as a part of, or in connection with, an electrical installation."
Ground Fault, Article 100.1: "An unintentional, electrically conducting connection between an ungrounded conductor of an
electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic
raceways, metallic equipment, of earth.
Listed, Article 100.1:
"Equipment, materials, or services included in a list published by an organization that is
acceptable to the AHJ...and whose listing states that either the equipment, material, or service ...
has been tested and found suitable for a specified purpose."
Portable Equipment, Article 520.2: "Equipment fed with portable cords or cables intended to be moved from one place to
another."

lighting instrument is designed to facilitate the
operation of the overcurrent device.
Nearly everyone has heard about or been
taught the importance of grounding. Some of
the truths we have learned can unfortunately
lead to confusion. Let's look at three examples.
1. Electricity will take the path of least
resistance. This piece of common sense is
true but misleading, because it leaves out
the fact that electricity will take any path
available to it, not just the one smooth path
that has the least amount of resistance.
Giving electricity a path of least resistance
to ground alone will not necessarily protect

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you from injury.
2. Electricity would rather go to ground
if given the option. This is the statement
many of us were taught to explain why we
ground things. It is misleading, however,
because it implies that giving electricity
more options-the more paths to
ground-is better. The problem here is
that if electricity has multiple places to
go of unpredictable resistances, this may
keep the current low, which in turn will
not give the overcurrent device a reason to
operate.
3. It takes very little electricity to stop the

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heart so we limit it by giving it a path
to ground. This is true, but again there
is more to the story. Different sources
suggest different thresholds for ventricular
fibrillation and other injuries, but here
we will use the National Institute for
Occupational Safety and Health's (NIOSH)
2009 student manual, Electrical Safety
(Pub. 2009-113). It tells us that it may
take as little as 0.0752A to stop the heart.
A 1000W PAR can draw around 8A; so,
thinking that a path to ground from an
accidently energized frame of a lighting
instrument is, in and of itself, going to

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