A change to 338.10 of the 2002 NEC

July 8, 2004

A change to 338.10 of the 2002 NEC is meant to clarify that when Type SE service-entrance cable is used for interior wiring

Mike Holt

A change to 338.10 of the 2002 NEC is meant to clarify that when Type SE service-entrance cable is used for interior wiring it needs to comply with the installation requirements of Parts I and II for NM cable, but not the 60°C conductor ampacity limitations of 334.80. This change simply reverts the text back to the requirements contained in the 1996 NEC. It’s important to note that Type USE cable can't be used for interior wiring because it isn't listed for this application.

Now consider the following example calculation:

Sec. 424.3(B) requires the branch-circuit conductor for electric space heating equipment to have an ampacity of not less than 125% of the total heating load. A 10kW heater with a 3A blower motor must be wired with a conductor that has an ampacity of at least 56A (10,000W ÷ 240V + 3A). Therefore, it's acceptable to use 4 AWG NM cable or 6 AWG SE cable.

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.