6-49a Log #CP604 NEC-P06
Final Action:
Accept
(310.15(B)(7))
________________________________________________________________
TCC Action: The Correlating Committee directs that the panel clarify
their action on this proposal.
The Correlating Committee also directs the panel to revise the
Informational Note as it contains permissive language, i.e. the word
?may?. This action will be considered as a public comment.
Submitter:
Code-Making Panel 6,
Recommendation:
Delete Table 310.15(B)(7) and replace 310.15(B)(7) with
the following:
(7) 120/240 Volt, Single-Phase Dwelling Services and Feeders.
For service and feeder conductors of 120/240-volt, single-phase, individual dwelling unit
one-family, two-family, and multifamily service ratings from 100 through 400
amperes, an adjustment factor of 0.83 of the service ampere rating shall be
permitted to be used to determine the size of the ungrounded conductors. The
grounded conductor shall be permitted to be smaller than the ungrounded
conductors, provided that the requirements of 215.2, 220.61, and 230.42 are
met.
Informational No. 1: The conductor ampacity may require other correction or
adjustment factors applicable to the conductor installation.
Informational No. 2: See example DXXX in Annex D.
Substantiation:
It was determined that during the 1956 Proceedings of the
Sixteenth NFPA Annual Meeting that 84 percent was used to establish the
aluminum residential service conductor size. However, if the panel used 84
percent in the changed language, it would have resulted in larger sizes for some
of the conductors, compared to the sizes in the 2011 NEC. Since the panel had
no technical substantiation to justify these changes, 83 percent was used to
maintain consistency with the sizes in the 2011 Table 310.15(B)(7).
In order to address the various proposals submitted suggesting changes to
310.15(B)(7), the panel analyzed the existing language and determined that the
conductor sizes in Table 310.15(B)(7) are equivalent to those that would be
used if a 0.83 multiplier was applied to each service ampere rating. The
resulting conductor size will be the same as existing text in Table 310.15(B)(7),
if the same conductor types and installation conditions are applied.
The informational note was added to make it clear that adjustment and
correction factors apply depending on conditions of use. This action no longer
requires the definition of a ?main power feeder? in 310.15(B)(7).
Panel Meeting Action: Accept
Number Eligible to Vote: 10
Ballot Results:
Affirmative: 9 Negative: 1
