Submitter: Wayne Foster, Lynn Electric Inc.
Recommendation: Add new text to read as follows:
Exception No. 6: derating factors shall not apply to cables run in bored holes,
or cut notches in joists or interior walls in dwellings under the following
(1) Where these cables are run in bored holes in a wall, floor, or ceiling
space, and where the ambient temperature will not exceed 30?C in normal use
(2) Where the ambient temperature will not exceed 30?C in normal use and
(3) Where these cables are not larger than No. 12 Cu or No. 10 AL
(4) This exception shall not apply where more than two NM cables
containing two or more current carrying conductors are bundled together and
pass through wood framing that is to be fire- or draft stopped using thermal
insulation or sealing foam, a required in 334.80.
Substantiation: Where there are cables run in bored holes in joists with
spacing between each joist, the maximum load on these cables, will most likely
never be used because of the load profiles in dwelling units. The temperature
rise of these cables is minimal, under these conditions. By limiting this
exception to 15 and 20 ampere circuits, the range, dryer, electric furnace, etc.
are excluded and the likelihood of more than one or two heavily load circuits
The code now requires multiple holes to be bored in floor joists to
accommodate the runs and building regulations limit the amount of these holes
that can be safely bored into floor joist. This places an undue burden on the
electrician to find exit routing from panelboads. This proposal will provide
some relief from the stringent requirements.
And that the dwelling unit load is so diverse and that those circuits are almost
totally for convenience: therefore the need for derating is not required as
circuits will be used minimally and in small groups. The heaviest loaded
circuits would likely be one or two small appliance branch circuits, a bathroom
receptacle circuit, and a laundry circuit. Those circuits, mixed in with the other
circuits would not require derating.
Panel Meeting Action: Reject
Panel Statement: Testing data has shown that the submitters substantiation is
not accurate.Number Eligible to Vote: 11
Ballot Results: Affirmative: 11