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July 11, 2006 A Prism Business Media Publication Vol. IV No. 13



CONTENTS
210.20 Overcurrent Protection

What's Wrong Here?

Code Q&A

Code Quiz

State of Washington Adopts Emergency Rule for Selective Coordination


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    Top 50 NEC Rules
    210.20 Overcurrent Protection
    By Mike Holt
    Size branch-circuit overcurrent protection devices no less than 125% of the continuous loads plus 100% of the noncontinuous loads they serve. See 210.19(A)(1) for branch-circuit conductor sizing requirements. Where the assembly and the overcurrrent protection devices are both listed for 100% continuous load operation, you can size the branch-circuit protection device at 100% of the continuous load. However, note that equipment suitable for 100% continuous loading is rarely available in ratings under 400A.

    Protect branch-circuit conductors against overcurrent in accordance with 240.4. Protect branch-circuit equipment in accordance with 240.3.

    Editor's note: This information was extracted from Mike Holt's textbook, Understanding the National Electrical Code


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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: Something is missing in this installation.

    Code Q&A
    By Mike Holt
    Q. Can Table 310.15(B)(6) be used to size service conductors for a duplex?

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

    Code Quiz
    By Steven Owen
    Q. When installing electric heat-tracing cables and heating panels in industrial installations (where ground fault alarm indication is provided and the operation cannot tolerate a ground fault condition that would normally open the circuit overcurrent device), which of the following choices best meets the requirements outlined in Art. 422 for protection of these components?
    A) Ground fault protection for equipment is not required for the heating cables and the heating panels where qualified persons service the installation and continued operation is necessary for safe operation of the equipment or process. However, the heating wires or cables must have a grounded conductive covering.
    B) GFCI protection is required for the heating cables only, and the cables must have a grounded conductor covering.
    C) GFCI protection is required for the heating cables and heating panels.
    D) Ground fault protection for equipment is required for the heating cables and the heating panels, and the cables must have a grounded conductor covering.

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


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    Code News Update
    State of Washington Adopts Emergency Rule for Selective Coordination
    In a rule-making order filed on May 31, 2006, the chief electrical inspector of the State of Washington issued an emergency ruling that exempts existing buildings undergoing modification or renovation from the 2005 NEC requirements for selective coordination of emergency and legally required standby power systems. More specifically, the requirements for selective coordination described in 700.27 and 701.18 are not required in existing buildings or structures. However, the portion of the emergency or legally required standby system for any new building or structure not located within the existing building or structure must still comply with the requirements of 700.27 and 701.18.

    The reasons behind this emergency ruling were noted in the rule-making order, which noted in part: "It was recently brought to the department's attention that upgrading existing buildings to a coordinated system is placing a significant economic burden on building owners and businesses. Also, due to the increased regulatory requirements associated with the coordinated systems, facilities such as hospitals and schools will have to be placed out-of-service for extended periods of time."

    The ruling goes on to say, "The emergency rule will provide building owners and businesses financial relief from having to upgrade the existing emergency systems without comprising public safety."


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