A Confusing Question HELP!!

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k d

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The maximum circuit ampacity rating of ten non-jacketed MC cables bundled together longer than 24 inches, each cable containing two - 12 AWG THHN copper current carrying conductors, supplied from breakers having 75 degree C. terminations for lighting loads shall NOT exceed:

A) 15 Amperes
B) 20 Amperes
C) 25 Amperes
D) 30 Amperes
 
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vsullivan

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Re: A Confusing Question HELP!!

Start with 330.80 which states, in part, "The ampacity of Type MC cable shall be determined in accordance with 310.15 or 310.60 for 14 AWG and larger conductors...". Then, go to 310-15 (B) (2) Exception 5, which states, "Adjustment factors shall not apply to Type AC cable or to Type MC cable without an overall outer jacket under the following conditions: (a) Each cable has not more than three current-carrying conductors. (b) The conductors are 12 AWG copper. (c) Not more than 20 current-carrying conductors are bundled, stacked, or supported on "bridle rings." Finally, look at 240.4 (D), which states,"Unless specifically permitted in 240.4(E) through (G), the overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper..."
 
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