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October 9, 2008 A Penton Media Publication Vol. VI No. 19


CONTENTS
250.52 Grounding Electrodes

What's Wrong Here?

Code Q&A

Code Quiz

Canadian Electrical Code Moves to Three-Year Revision Cycle

Learn Everything You Need To Know About Arc Flash


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    Top 2008 Code Changes















    250.52 Grounding Electrodes
    The requirements for a concrete-encased electrode now include vertical electrodes as well as what to do when multiple isolated concrete-encased electrodes are present.

    (A) Electrodes Permitted for Grounding.
    (3) Concrete-Encased Grounding Electrode    . A concrete-encased electrode is an electrode that is encased by at least 2 inches of concrete, located horizontally near the bottom or vertically within a concrete foundation or footing that is in direct contact with the earth consisting of one of the following:

    • Twenty feet of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars bonded together by the usual steel tie wires not less than ½ inch in diameter, or
    • Twenty feet of bare copper conductor not smaller than 4 AWG
    If a moisture/vapor barrier is installed under a concrete footer, then the steel rebar is not considered a concrete-encased electrode.

    Where multiple concrete-encased electrodes are present at a building or structure, only one is required to serve as the grounding electrode system.

    The grounding electrode conductor to a concrete-encased grounding electrode isn't required to be larger than 4 AWG copper [250.66(B)].

    The concrete-encased grounding electrode is also called a "Ufer Ground," named after Herb Ufer, the person who determined its usefulness as a grounding electrode in the 1960s. This type of grounding electrode generally offers the lowest ground resistance for the cost.

    The requirements for concrete-encased electrodes have been expanded to allow structural steel rebar in vertical foundations to be suitable as a grounding electrode, as long as it meets all of the requirements for horizontal structural steel rebar electrodes. In addition, the 2008 NEC clarified that in a building or structure where multiple isolated concrete-encased electrodes are present, such as for spot footings, only one of these "present" electrodes will be required to be used. The purpose of the NEC [90.1] is the "practical safeguarding of persons and property," and requiring all of the concrete-encased electrodes to be bonded together served no safeguarding purpose.

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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: Do you use protection?
    Code Q&A
    By Mike Holt
     Q. Our utility requires a nonfused disconnect upstream of the meter and service disconnect for certain services. Is this legal?

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


    Code Quiz
    By Steven Owen
     Q. When grounding the frames of metal-enclosed power switchgear, which of the following methods listed here is the only one that is permitted by the 2008 NEC?

      1. A 6 AWG equipment bonding jumper from a nearby effectively grounded steel column.
      2. A 6 AWG grounding electrode conductor connected to a driven ground rod adjacent to the equipment.
      3. GFPE protection (30mA trip setting).
      4. A properly sized equipment-grounding conductor.

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

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    Code News Update
    Canadian Electrical Code Moves to Three-Year Revision Cycle
    According to a news brief in the July/August 2008 issue of Electrical Line magazine, a Canadian business trade publication, the 21st edition of the Canadian Electrical Code, Part I (CEC) in early 2009 will signal the beginning of its move from a four-year to three-year cycle. One benefit of this change may be a closer correlation between the CEC and the NEC. The new three-year cycle will also allow the Canadian Standards Association (CSA) -- publisher of the CEC -- to more quickly accept new safety requirements and product technologies available to the electrical market.

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    Shows and Events

    Learn Everything You Need To Know About Arc Flash

    In two informative and interest-filled days, you'll learn about:
    • Original Ralph Lee Paper Assumptions and Resulting Calculations
    • Requirements for Development of an Arc Flash Analysis
    • Conducting an Arc Flash Site Analysis
    • Differences Between NFPA 70E and IEEE 1584
    • Arc Flash Hazard Prevention by Design
    • Software Tools and Arc Flash
    • Calculating Arc Flash Energy Levels
    • Low Voltage Shock Damage to Human Body
    • Advancements in Personal Protective Equipment
    • Case Studies of Arc Flash Hazard Mitigation
    Whether you're an electrician, contractor, engineer, designer, or plant/facility maintenance person, you can't afford to miss this event. Symposium is scheduled to take place October 14-15 in Boston.

    For more information and to register online, go to http://ecmuniversity.com/arc-flash-conferences/.

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