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5-290 Log #1511 NEC-P05 Final Action: Reject
(250.122(B))
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TCC Action: The Technical Correlating Committee directs that the panel
clarify the panel action to Reject this proposal while also providing revised
text.
This action will be considered by the panel as a public comment.
Submitter: Charles E. Beck, Affiliated Engineers NW, Inc.
Recommendation: Revise text to read as follows:
(B) Increased in Size. Where ungrounded conductors are increased in size
from the minimum size that has sufficient ampacity for the intended
installation, grounding conductors, where installed, shall be increased in size
proportionally according to the circular mil area of the ungrounded conductors.
Substantiation: NOTE: This is the first of two similar proposals that I am
submitting. Each is intended to resolve the same concern, but the two
accomplish this resolution in different ways. The following substantiation
paragraph is identical for both.
This proposal would correct an error in the use of the English language. The
phrase “increased in size” is incomplete, without there being some reference
point from which to determine whether the size had been increased. The phrase
begs the question, “Increased from what?” Absent an answer to that question,
the paragraph is unenforceable.
An absurd example would be if a mechanical engineer decides to use a larger
pump than had appeared on the preliminary plans. As a result, the electrical
engineer’s final plans must show #10 wire, instead of the #12 shown in the
preliminary plans. Is that an “increase in size”? Certainly not, because the #12
does not have sufficient ampacity for the new, larger motor. A more practical
example would be if a project’s ambient temperature forces the use of a larger
wire, because of the correction factors of Table 310.16. Use of the smaller size
wire would not have been legal, because its ampacity, under the conditions of
use, was insufficient. Use of the next size larger wire was required, in order to
obtain the minimum ampacity for the application. Is that an “increase in size”?
It should not be, but the present wording of 250.122(B) does not make a clear
distinction on this point.
The wording of this article needs to clearly establish whether it is intended to
mean “an increase in size from a size that could have been legally used in this
application,” as opposed to “an increase in size from the value shown in the
ampacity tables, before the application of any adjustment or correction factors.”
Panel Meeting Action: Reject
Revise text to read as follows:
(B) Increased in Size. Where ungrounded conductors are increased in size from
the minimum size that has sufficient ampacity for the intended installation,
grounding conductors, where installed, shall be increased in size proportionally
according to the circular mil area of the ungrounded conductors.
Panel Statement: The recommended text does not improve the understanding
of the provision of Section 250.122(B). The panel concludes there are
numerous reasons for increasing the size of the ungrounded conductors in
addition to ampacity adjustment and correction factors such as considerations
for voltage drop, overcurrent device performance, and other engineering
factors. The NEC is a minimum requirement and this section is addressing any
increase over the minimum required by code.
Number Eligible to Vote: 16
Ballot Results: Affirmative: 15 Negative: 1
Explanation of Negative:
BRENDER, D.: This proposal has merit and should have been accepted in
principle. Establishing the threshold from which conductors are increased
would add clarity to the existing rule. The reported Panel vote of Reject is
inconsistent with the panel action as a revised Panel action is reported.
