December 8, 2005 A PRIMEDIA Property Vol. III No. 23

Article 800 -- Communications Circuits, Part IV. Grounding Methods,
800.100 Cable and Primary Protector Grounding

The Case of the Mysterious Switch

What's Wrong Here?

Code Q&A

Code Quiz

Seattle Adopts 2005 NEC

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    Top 2005 Code Changes
    Article 800 -- Communications Circuits, Part IV. Grounding Methods 800.100
    Cable and Primary Protector Grounding

    By Mike Holt

    New FPN alerts the Code user that limiting the length of the grounding conductor for the primary protector should reduce voltages that may develop between the building's power and communications systems during a lightning event. (Note: Code text has been paraphrased.)

    What the Code says:
    (A) Grounding Conductor. The grounding conductor must be:

    (4) Length. The grounding conductor must be as short as practicable. In one- and two-family dwellings, the grounding conductor cannot exceed 20 ft.

    FPN: Limiting the length of the grounding conductors reduce differences in potential between the building's power and communications systems during lightning events.

    Exception: Where it isn't practicable to limit the grounding conductor to 20 ft for one- and two-family dwellings, a separate ground rod not less than 5 ft long [800.100(B)(2)(2)] with fittings suitable for the application [800.100(C)] must be installed. The additional ground rod must be bonded to the power grounding electrode system with a minimum 6 AWG conductor [800.100(D)].

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    Nightmare Installations
    The Case of the Mysterious Switch
    A customer contacted us for a seemingly simple trouble call. Having some difficulty after replacing his electric water heater, he told us he had switched the breaker off, checked to make sure the power was off, and then removed the old heater. After installing the new heater, he turned the breaker back on -- but now there was no voltage present.

    My helper and I decided to drive out to the house and check things out. The breaker was good, but when we rang it out we discovered there was no continuity from the panel to the new heater. There were no junction boxes in the path! So what happened?

    A trip into the attic revealed that the home run traveled down a wall by the kitchen sink. The hot water heater was on the floor below. A signal from the toner found the culprit. For some reason, there was a 2-pole switch by the sink. Why, we don't know. The owner never knew what that switch was for -- until now (when someone in the house inadvertently turned it off).

    Greg Joachim
    Kihei, Maui, Hawaii

    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

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

    Hint: Knot this time — or anytime for that matter.

    Code Q&A

    By Mike Holt

    Q. How far away must a 120/208V, 3-phase panelboard be located from a janitorial closet sink?

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

    Code Quiz

    By Steven Owen

    Q. When grounding a large bridge crane in an industrial facility, such as a paper mill or steel mill (or any other location), which of the following statements is correct?

    A) The trolley frame and bridge frame are considered to be electrically grounded through the bridge and trolley wheels and its respective track.
    B) The trolley frame and bridge frame are not considered to be electrically grounded through the bridge and trolley wheels and its respective track.
    C) All moving parts, including the trolley and bridge frame that have a metal-to-metal bearing surface are considered to be effectively grounded.
    D) An equipment grounding conductor shall be installed along the entire length of the crane rails, bridge, and trolley. This conductor may be placed anywhere on the metal frame of the crane assembly.

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

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    Code News Update
    Seattle Adopts 2005 NEC
    Effective Oct. 22, 2005, the city of Seattle has adopted the 2005 edition of the National Electrical Code, according to the November issue of electroindustry. The 2005 Seattle Electrical Code consists of the 2005 National Electrical Code, the Washington State Electrical Code (WAC 96-46B), and Seattle amendments.

    Approved in September by the Seattle City Council, the 2005 Seattle Electrical Code was developed by the Electrical Code Review Committee throughout meetings during the spring and early summer.

    According to the article, a few significant amendments to the 2005 edition include:
    • A new requirement for two sets of plans with applications for equipment rated 400A or more; and for services, feeders, and power supplies for emergency, standby and fire pump systems.

    • An amendment that adds utility raceways that are metallically connected to other service equipment to the list of equipment required to be bonded.

    • A provision allowing MC cable for branch circuits, with prior approval of the city.

    • A requirement for a standby power source kept independent of other wiring and equipment, and separate from the same raceway, cable box, or cabinet with wiring for low-rise shaft pressurization systems, or elevators that are used as accessible means of egress.

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