February 13, 2006 A Prism Business Media Publication Vol. IV No. 3



CONTENTS
Trick, but No Treat

What's Wrong Here?

Code Q&A

Code Quiz

Rhode Island Adopts Electrical Code

Understanding and Applying the 2005 NEC


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    Nightmare Installations
    Trick, but No Treat
    While working a Halloween show a number of years ago, I ran into an interesting situation. In what is typical of entertainment power in a theater, the house electrician tied in the raw power tails of the temporary 200A-per-leg 3-phase light dimmer panel to the ancient house disconnect panel. Everything seemed to be working fine until about one hour before the show was to open. It was at this point I smelled the "uh, oh" sort of electrical smell we all dread.

    At first, I did not see any smoke, and everything was still working. However, my nose soon led me straight to the old
    3-phase house disconnect panel. The panel looked like a Smoky Joe BBQ with small tufts of smoke curling out of it. Power at the dimmer rack was immediately shut down, and the disconnect knife was thrown killing the feed. After 5 minutes or so of cooling down, the panel door was opened. What was found was very disturbing.

    Sometime in the past, someone upgraded the undersized neutral wire going into the old panel. In doing so, he pulled an additional parallel neutral wire into the show disconnect panel. Unfortunately, this new wire would not fit in with the current bus bar arrangement. So instead of replacing the entire panel or wiring the job correctly, some enterprising electrician used a piece of wood rather than the proper high-temperature material to hold the new makeshift neutral bus bar in place. The piece of wood was literally turned into charcoal under the heavy temporary show load.

    A temporary fix was performed, and the show went on as planned. But I always wonder what would have happened if the neutral bus bar had broken loose from its "charcoal base" and hit one of the hot legs.

    Bob Ursdevenicz
    Omaha, Neb.



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    Code Challenge
    What's Wrong Here?
    By Joe Tedesco

    Think you know how this installation violates the NEC? Visit EC&M's Web site to see the answer.

    Hint: The case of the undressed current transformers.


    Code Q&A
    By Mike Holt
    Q. What size wire and breaker is required for an air-conditioner whose nameplate specifies the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A? The terminals on the equipment are rated 75°C.

    Visit EC&M's Web site to see the answer.


    Code Quiz
    By Steven Owen
    Q. What is the maximum number of overcurrent devices permitted in a lighting and appliance branch-circuit panelboard? What is the maximum number of overcurrent devices permitted in a power distribution unit (PDU) of an information technology system?
    A) 36 / 42
    B) 42 / 42
    C) 54 / 42
    D) 54 / 54

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


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    Code News Update
    Rhode Island Adopts Electrical Code
    The Rhode Island Legislative Regulation Committee recently approved adoption of the Rhode Island State Electrical Code (SBC-5-2005). The state code is based on the 2005 National Electrical Code and features five amendments, which all address administrative and enforcement provisions -- four in Article 90 and one in Article 110. The Rhode Island State Electrical Code has an effective date of January 1, 2006.


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    Visit www.NECcode.com and stay current with important industry issues.


    Shows and Events
    Understanding and
    Applying the 2005 NEC

    The Electric West Exposition & Conference, March 1-3, 2006 at the Las Vegas Convention Center, will be offering over 50 conference courses and professional advancement courses on a wide variety of electrical topics. Session NEC01, Understanding and Applying the 2005 NEC, will be taught by noted NEC expert and EC&M Code consultant Mike Holt of Mike Holt Enterprises, Inc. This course will help you understand the concepts necessary to design, install, inspect, measure, and troubleshoot electrical systems, as well clear up confusing and seemingly conflicting or controversial NEC rules. CEU credits are available upon successful completion of this course. For more information and to register visit www.electricshow.com.

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