December 22, 2005 A Prism Business Media Property Vol. III No. 24



CONTENTS
Article 820 -- Community Antenna Television and Radio Distribution Systems
Part VI. Listing Requirements
820.182 CATV Raceways

The Mysterious Blinking Christmas Tree

What's Wrong Here?

Code Q&A

Code Quiz


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    Top 2005 Code Changes
    Article 820 -- Community Antenna Television and Radio Distribution Systems
    Part VI. Listing Requirements
    820.182 CATV Raceways

    By Mike Holt

    New subsections added to recognize the use of raceways designed for coaxial cables. (Note: Code text has been paraphrased.)

    What the Code says:
    (A) Plenum Coaxial Raceways. Plenum-rated raceways for coaxial cables must be listed as being suitable for use in ducts, plenums, or other environmental air spaces.
    (Text new to the Code is underlined.)

    Behind the change: Where used in ducts, plenums, or other environmental air spaces, listed plenum communications raceway can only contain Type CATVP cable [820.179(A)].

    What the Code says:
    (B) Riser Coaxial Raceway. Riser rated raceways for coaxial cables must be listed as being suitable to be run vertically through more than one floor.

    Behind the change: Listed riser-rated coaxial raceways run vertically and penetrating more than one floor can only contain CATVR and CATVP cables [820.179(B)].


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    Nightmare Installations
    The Mysterious Blinking Christmas Tree
    I received a residential trouble call from a new customer whose Christmas tree lights would just come on and go off by themselves. The lights were plugged into a receptacle at the bottom of their spiral staircase.

    After finding no problems in the receptacle wiring of the branch circuit serving the tree (the lights were off at this time), I decided to check other receptacles in the area for power. Finding no problems, I went back to the tree, and the lights were now on. However, they quickly went off. I thought that plugging the tester into the receptacles might have helped make the circuit so I did it one receptacle at a time. Finally, after checking the receptacles in the master bathroom the tree lights were working again. But they soon went out! Naturally, I thought the wiring problem was somewhere in the bathroom and proceeded to take out the switches and receptacles one at a time.

    After checking all the connections, I finally found a motion sensor in the master bathroom walk-in closet that controlled a light fixture (which was located partially under the staircase). The load side of the sensor was not only wired to serve the light in the closet but it also fed the receptacle where the tree was plugged in. Every time someone would walk to the closet, the tree lights would come on for a limited time, and then automatically turn off. Since this was such a large house nobody could relate the two occurrences.

    M. Vince Brewer
    Frisco Electric, Inc.




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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: Too much of a good thing.

    Code Q&A

    By Mike Holt

    Q. What are the NEC grounding requirements for a satellite dish?

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


    Code Quiz

    By Steven Owen

    Q. What is the minimum circuit ampacity and minimum size conductor required for the feeder conductors supplying the following group of electric arc welders?

    • one each -- 80A rated, non-motor generator, 100% duty cycle.
    • one each -- 70A rated, motor generator, 90% duty cycle.
    • one each -- 60A rated, non-motor generator, 70 % duty cycle.
    • one each -- 50A rated, non-motor generator, 80% duty cycle.
    • four each -- 40A rated, motor generator, 60% duty cycle.
    • four each -- 25A rated, non-motor generator, 40% duty cycle.
    Terminals at the feeder overcurrent device and in the welder disconnects are rated 75°C. The feeder consists of one conductor per phase, which is specified as THHN insulated, dry location.

    A) 350 kcmil THHN
    B) 400 kcmil THHN
    C) 500 kcmil THHN
    D) 600 kcmil THHN

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


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