215.2 -- Minimum Rating and Size
Faces of the Code
A Place of Their
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Top 2005 Code Changes
215.2 -- Minimum
Rating and Size
By Mike Holt
A new sentence requires the feeder grounded (neutral)
conductor to be sized so that it has adequate fault-current capacity in
the event a short circuit occurs between an ungrounded conductor and
grounded (neutral) conductor. See 215.3 for the sizing requirements of
the feeder overcurrent protection device for continuous and
What the Code says:
(A) Feeders Not More Than 600V
(1) General. The minimum feeder-circuit
conductor size, before the application of any adjustment or correction
factors, must be no less than 125 percent of the continuous loads, plus
100 percent of the noncontinuous load based on the terminal temperature
rating ampacities as listed in Table 310.16 [110.14(C)].
(Text new to the Code is underlined.)
Behind the change: Load calculations often result in a
grounded (neutral) conductor that is very small in comparison to the
ungrounded conductors. Should a fault occur from an ungrounded
to a grounded (neutral) conductor, the grounded (neutral) conductor
could be damaged before the overcurrent protection device opens if it
isn't sized to carry the available fault current.
What the Code says:
(neutral) conductor must not be sized smaller than specified in 250.122
for the equipment grounding (bonding) conductor, based on the rating of
the feeder protection device. (Text new to the Code is
Behind the change: Circuit conductors must have sufficient
ampacity, after ampacity adjustment, to carry the load, and they must
protected against overcurrent in accordance with their ampacity [215.3
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my hands. As I opened other j-boxes, I discovered that someone had
wired the entire basement in #18 wire lamp cord, and due to the
condition, it was brittle and crumbling apart. It was a miracle that
place didn't burn to the ground, considering the fact that nothing was
on a GFCI and it was on a breaker known for its slow tripping nature.
When I asked the owner who had wired the basement, he reluctantly
admitted that he had. When I asked him why he chose this wire, he said,
"That's what they use on lamps, and that's all we were going to plug
into the receptacles."
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What's Wrong Here?
By Joe Tedesco
How does this
installation violate the NEC?
Hint: This installation proves that bad things happen in
By Mike Holt
Q. Can service drop conductors be supported by
See the answer.
By Steven Owen
The load on the service grounded "neutral" conductor in
a newly designed commercial office building (208/120V 3-phase, 4-wire
system) is 475A. The loads being served are nonlinear. The ungrounded
service entrance conductors were sized based a calculated load of 775A
that took into account numerous 3-phase loads, such as air conditioning
and heating, that have no neutral load. What is the demand load, if
on the grounded "neutral" conductor of this system?
- 775A, neutral has to be the same size as phase
- 392.5A, 70% demand on portion exceeding 200A
- 475A, no reduction permitted when serving nonlinear loads
- 406.25A, 75% demand on portion exceeding 200A
Visit EC&M's Web
for the answer and explanation.
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Faces of the Code
Member, Code-Making Panel 15
By the time he graduated from Clemson's electrical
engineering program and the Coast Guard's officer candidate school, Jim
Duncan had had enough of dry land. In the hopes of spending months at
sea and traveling to the North and South Poles, he packed up his things
in Baltimore and asked to be stationed on an icebreaker in the Pacific.
Instead, he received a desk assignment in Seattle at the Coast Guard's
facilities design and construction command -- far from the sea-faring
adventure he wanted.
But the disappointment he felt at not getting to travel the world
soon replaced by the satisfaction he took from seeing people move into
the buildings he was designing. Four years after moving to Seattle, he
left the Coast Guard and joined Sparling, then a small electrical
engineering firm of only 20 employees. He designed electrical systems
for military buildings, commercial high rises, and TV stations, but it
was his work on health-care facilities -- a market he actively pursued
on his way to becoming CEO -- that would shape much of his career and
introduce him to Code-Making Panel 17 (and later Panel 15 when article
assignments were shifted).
Duncan joined CMP-17 in 1989 and became a principal in 1993, and he
continued to contribute to the health-care industry through a variety
other outlets. Aside from helping to write the IEEE White Book --
Recommended Practice for Electrical Systems in Health Care Facilities,
he undertook an initiative to change the way emergency generators are
sized for hospitals. The Code was changed to size them based on
the real rather than connected loads. "I'm very proud of that," he
"We're saving health care dollars while increasing emergency system
reliability because the generators are now tested close to their rated
More than 30 years after the Coast Guard temporarily denied him his
dreams of seeing the world, Duncan has since done it on his own,
traveling to places like New Zealand, India, and South Africa. Growing
Sparling to the $18 million-a-year company it is today, on the other
hand, took the contributions of many, including some from the
Code-making panels. "I really enjoy being able to pick up the phone and
call colleagues and friends to ask their opinion on a design issue," he
says of his fellow members. "They're an amazing resource."
A Place of Their Own
Art. 517 for health-care facilities had its own
dedicated Code-making panel until the 2005 Code cycle when it was
into Panel 15 along with carnivals, motion picture studios, and
theaters. With life safety on the line, should the requirements for
hospitals and critical care facilities have their own panel? Visit www.ecmweb.com to tell us.
Inspectors, if you thought you got a lot of calls before, wait a couple
weeks. CodeWatch readers say they call on their local inspector more
than anyone else for clarification when they don't understand a Code
rule, and with the 2005 NEC only a few weeks old, it's only a matter of
time before the questions start to pop up.
And for those of you with neighbors who still have the holiday
or are just too lazy to take down their lights, Joseph Greco, a
licensed electrician in New Jersey, recently sent us another
for getting the word out about Art. 590's limits on temporary holiday
lights that takes advantage of everyone's favorite favorite home
appliance: the TV. Visit EC&M's Web
site for his idea.
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