April 22, 2005 A PRIMEDIA Property Vol. III No. 8




CONTENTS
310.15 -- Conductor Ampacity

The Basement Boogeyman

What's Wrong Here?

Code Q&A

Code Quiz

Getting Around


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    Top 2005 Code Changes
    310.15 -- Conductor Ampacity
    By Mike Holt
     Text was added to clarify that the reduced size feeder conductors permitted in Table 310.15(B)(6) only apply for individual dwelling units of one-family, two-family, and multifamily dwellings. (Note: Code text has been paraphrased.)

    What the Code says:
    (B) Tables.
    (6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family and multifamily dwellings, Table 310.15(B)(6) can be used to size 3-wire, single-phase, 120/240V service or feeder conductors that serve as the main power feeder to a dwelling unit.     (Text new to the Code is underlined.)

    Behind the change: The definitions in Article 100 for one-, two-, and multifamily dwelling units limited this application to a one-family dwelling in a separate building.

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    Nightmare Installations
    The Basement Boogeyman
    Years ago when I was a chief engineer for an electric utility, we found a residential customer on the system who had a 2,400 -- 120/240V, oil-filled, pole-top transformer in their basement. It rested on the basement floor -- completely unguarded -- with the energized primary terminals exposed and no barrier to keep the residents from coming into contact with them. The secondary from the transformer went to his meter, which was also in the basement. When we checked into the records, we found that the transformer had been in service at this residence since the '30s (we found it in the '90s). Families had been living in the house for 60 years, yet miraculously no one was ever injured. Of course, the problem was corrected on the same day we discovered it.
    Richard Barker
    Marietta, Ga.
    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
     How does this installation violate the NEC?

    Hint: First concentrate on what's not in the picture and then on what shouldn't be in the picture.

     Code Q&A
    By Mike Holt
     Q. Does the Code limit the total ampere rating of all circuit breakers in a panel? For example, could the total ampere rating of all circuit breakers in a 100A panel exceed 100A?
    See the answer.
    Code Quiz
    By Steven Owen
     Consider the following situation: Three black 12 AWG THHN conductors pass directly through a box, uncut and unspliced. Three red 12 AWG THHN conductors are looped in the box. The loop measures 12 inches for each conductor. Six white (grounded) conductors are also looped with 12-inch loops. As would be expected, a green 12 AWG equipment grounding conductor originates at the panelboard and is installed with the branch-circuit conductors, cut into two pieces (each measuring 6 inches) within the box. An equipment bonding jumper is also pigtailed within the box (to the equipment grounding conductors), bonding the equipment grounding conductors to the box, but it doesn't leave the box. What's the minimum cubic inch capacity for the box?

    1. 29.25 cu. in.
    2. 31.50 cu. in.
    3. 33.75 cu. in.
    4. 49.50 cu. in.

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

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    Speak Out
    Getting Around
    We've heard that some contractors think the NEC is "too safe" and that if they want to remain competitive on some projects they have to look for ways to "get around" certain requirements. How often do you see others take this course of action on jobsites? Visit EC&M's Web site to tell us.

    Nearly one in five CodeWatch readers are still using the 1999 Code, but that's not what concerns one reader who requested we not reveal his name. The unidentified 30-year veteran of the electrical field is tired of the inconsistent application of the NEC he witnesses in his jurisdiction. "Many view the NEC as a 'pick-and-choose' type of electrical code," he wrote. Visit EC&M's Web site to read his comments.

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