310.15 -- Conductor Ampacity
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Top 2005 Code Changes
310.15 -- Conductor
By Mike Holt
Text was added to clarify how each current-carrying
conductor of a parallel conductor set is to be treated when applying
ampacity adjustment factors of Table 310.15(B)(2)(a). (Note:
text has been
What the Code says:
Table. The allowable conductor ampacities listed in Table 310.16 are
based on conditions where the ambient temperature isn't over 86°F
and no more than three current-carrying conductors are bundled
(2) Ampacity Adjustment
(a) Conductor Bundle. Where the number of current-carrying
conductors in a raceway or cable exceeds three, or where single
conductors or multiconductor cables are stacked or bundled in lengths
exceeding 24 in., the allowable ampacity of each conductor, as listed
Table 310.16, must be adjusted in accordance with the adjustment
contained in Table 310.15(B)(2)(a). Each current-carrying conductor
of a paralleled set of conductors must be counted as a current-carrying
conductor. (Text new to the Code is underlined.)
Behind the change: The change was intended to resolve the
misconception presented by the language in 310.4 that paralleled
conductors are counted as a single conductor when applying the
provisions of 310.15(B)(2)(a).
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wasn't a problem, but the installer had fed the line side into the top
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that probably saved the tenant's life was that he had to stand on a
wooden chair on the damp basement floor to reach the fuse box.
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What's Wrong Here?
By Joe Tedesco
How does this
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Hint: The key word is "access."
By Mike Holt
Q. What's the maximum number of circuit breakers
permitted to be installed in a panel?
See the answer.
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Anyone interested in serving can download the application form at NFPA's Web
What's Your Code?
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