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Old 06-01-2015, 07:38 PM   #1
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SER cable touching insulation 1 side - derate?


Hello,

I am going to be installing a subpanel in my attached garage in the near future. Currently the wall is 2x4 stud wall with insulation stalled. I plan on scabbing on 2x3s to allow me to flush mount the panel and have a void in which to run my Romex through without having to fight insulation.

Where my service entrance cable enters from it will be in contact with 1 face of the insulation, but not enveloped in it. I know the NEC allows 10 feet/10% (whichever is shorter) to be in insulation without derating the ampacity, but for it to be considered "in insulation" does it need to be enveloped or just touching insulation? Thanks.
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Old 06-01-2015, 08:04 PM   #2
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Dont know where you got the 10'/10% from, but derating not necessary.
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Old 06-01-2015, 08:27 PM   #3
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I don't have direct access to the NEC, but this is what spurred my question:

Quote:
For interior branch circuits and feeders, Section 338.10(B)(4)(a) limits SE cable run through insulation to be limited to its ampacity in the 60°C column of Table 310.15(B)(16). Note that Section 310.15(A)(2) Exception allows up to 10 feet or 10% (whichever is less) to run through insulation without limiting the SE cable to 60°C.
From:
http://iaeimagazine.org/magazine/201...able-310-15b7/
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Old 06-02-2015, 12:37 PM   #4
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310.15 Ampacities for Conductors Rated 0–2000 Volts

(A) General.

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be used.

Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted
to be used beyond the point of transition, a distance equal to
3.0 m (10 ft) or 10 percent of the circuit length figured at the
higher ampacity, whichever is less.
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