January 24, 2005 A PRIMEDIA Property Vol. III No. 2

215.2 -- Minimum Rating and Size

Do-It-Yourself Disaster

What's Wrong Here?

Code Q&A

Code Quiz

Faces of the Code

A Place of Their Own

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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 noncontinuous loads.

    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 conductor 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:
    The feeder grounded (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 underlined.)

    Behind the change: Circuit conductors must have sufficient ampacity, after ampacity adjustment, to carry the load, and they must be protected against overcurrent in accordance with their ampacity [215.3 and 240.4].

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    Nightmare Installations
    Do-It-Yourself Disaster
    One day I was sent to a house to troubleshoot some receptacles in the basement that weren't working. Upon opening the first one, I was amazed to see what looked like wire lamp cords crumbling in 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 overload condition, it was brittle and crumbling apart. It was a miracle that the 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."
    Mark Grimes
    Wichita, Kan.

    Send your 200-word story to us and it may appear in a future issue of CodeWatch. Authors of stories chosen will receive $25.

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    Code Challenge
    What's Wrong Here?
    By Joe Tedesco
    How does this installation violate the NEC?

    Hint: This installation proves that bad things happen in threes.

    Code Q&A
    By Mike Holt
    Q. Can service drop conductors be supported by trees?
    See the answer.

    Code Quiz
    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 any, on the grounded "neutral" conductor of this system?

    1. 775A, neutral has to be the same size as phase conductors
    2. 392.5A, 70% demand on portion exceeding 200A
    3. 475A, no reduction permitted when serving nonlinear loads
    4. 406.25A, 75% demand on portion exceeding 200A

    Visit EC&M's Web site for the answer and explanation.

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    Faces of the Code
    Jim Duncan
    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 was 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 of 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 says. "We're saving health care dollars while increasing emergency system reliability because the generators are now tested close to their rated capability."

    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."

    Speak Out
    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 folded 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 spirit or are just too lazy to take down their lights, Joseph Greco, a licensed electrician in New Jersey, recently sent us another suggestion 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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