Code Q&A: Allowable Ampacity for Flexible Cords

Aug. 19, 2015

NEC rules on the ampacity requirements for flexible cords?

Q. What are the ampacity requirements for flexible cords?

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Find the Answer

A. Table 400.5(A)(1) lists the allowable ampacity for copper conductors in flexible cords and flexible cables and Table 400.5(A)(2) lists the allowable ampacity for copper conductors in flexible cords and flexible cables with not more than three current-carrying conductors at an ambient temperature of 86ºF [400.5(A)]. Where the number of current-carrying conductors in a cable or raceway exceeds three, the allowable ampacity of each conductor must be adjusted in accordance with the following multipliers:

Table 400.5(A)(3)(A)(3) Adjustment Factor
Number of Current Carrying Conductors	Multiplier
4 to 6	0.80
7 to 9	0.70
10 to 20	0.50

If the ambient temperature is other than 86°F, the flexible cord or flexible cable ampacity, as listed in Table 400.5(A)(1) or 400.5(A)(2), must be adjusted by using the ambient temperature correction factors listed in Table 310.15(B)(2)(a) (see Figure).

Temperature ratings for flexible cords and flexible cables aren’t contained in the NEC, but UL listing standards state that flexible cords and flexible cables are rated for 60°C unless marked otherwise.

See 400.13 for overcurrent protection requirements for flexible cords and flexible cables.

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.