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August 28, 2006 A Prism Business Media Publication Vol. IV No. 16

CONTENTS
Introducing the EC&M
E-Tradeshow

250.2 Definitions

What's Wrong Here?

Code Q&A

Code Quiz

State of Washington Revises Electrical Rules


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    Introducing the EC&M
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    Top 50 NEC Rules



















    250.2 Definitions
    By Mike Holt
     Why is grounding so difficult to understand? One reason is because many do not understand the definition of many important terms. So let's review a few important definitions contained in Articles 100 and 250.

    Bonding [100]. The permanent joining of metal parts together to form an electrically conductive path that has the capacity to conduct safely any fault current likely to be imposed on it.

    Author's comment: Bonding is accomplished by the use of conductors, metallic raceways, connectors, couplings, metallic-sheathed cables with fittings, and other devices recognized for this purpose [250.118].

    Bonding jumper [100]. A conductor properly sized in accordance with Article 250 that ensures electrical conductivity between metal parts of the electrical installation.

    Effective ground-fault current path [250.2]. An intentionally constructed, permanent, low-impedance conductive path designed to carry fault current from the point of a ground fault on a wiring system to the electrical supply source. The effective ground-fault current path is intended to help remove dangerous voltage from a ground fault by opening the circuit overcurrent protective device.

    Equipment grounding conductor [100]. The low-impedance fault-current path used to bond metal parts of electrical equipment, raceways, and enclosures to the effective ground-fault current path at service equipment or the source of a separately derived system.

    Author's comment: The purpose of the equipment grounding (bonding) conductor is to provide the low-impedance fault-current path to the electrical supply source to facilitate the operation of circuit overcurrent protection devices in order to remove dangerous ground-fault voltage on conductive parts [250.4(A)(3)]. Fault current returns to the power supply (source), not the earth! Refer to 250.118 for acceptable types of equipment grounding conductors.

    Click here to read the rest of this article.

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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: Is this meter coming or going?
    Code Q&A
    By Mike Holt
     Q. Can "line" and "load" conductors be installed in the same raceway?

    Visit EC&M's Web site to see the answer.
    Code Quiz
    By Steven Owen
     Q. When installing a new service for a separate building constructed on the top floor of a parking garage, it has been determined that the service conductors will have to be installed in rigid metal conduit (RMC) starting in the vault below grade of the first floor level of the parking garage. The structural engineer and the general contractor will not permit the service raceway to be encased within the concrete of the structure. What are some options available to the electrical contractor to make this installation possible, while maintaining compliance with the 2005 NEC?

    A) Install the RMC (containing service conductors), exposed from the vault to the first floor and up to the separate building on the top floor. Protection shall be provided where subject to potential severe physical damage.
    B) Encase the RMC in concrete, not less than 2 inches thick, in a separate chase provided specifically for this conduit.
    C) Encase the RMC with brick, not less than 2 inches thick, in a separate brick chase provided specifically for this conduit.
    D) If possible, install the service disconnect (for the separate building on the top floor) on the first floor in compliance with 230.70. From the first floor service disconnect location, install RMC, which will now contain feeder conductors to the separate building on the top floor. The conduit and feeder conductors will terminate in a disconnecting means that is installed per 225.32. This would permit the RMC to be exposed.

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

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    Code News Update
    State of Washington
    Revises Electrical Rules
    According to the August 2006 issue of Electroindustry, the State of Washington announced an early implementation of the 2006 edition of the Washington Electrical Rules. The story goes on to say, "Citing a relatively few number of revisions to the previous rules and little action required by legislation, the Electrical Section of the Department of Labor & Industries was able to move the schedule forward." The state revises its electrical rules annually.

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