Code Quiz of Day

Selection of Overload Device for Continuous-Duty Motor

Jan. 30, 2015

Part III of Article 430 focuses on motor and branch-circuit overload protection requirements.

When an overload device sized in accordance with 430.32(A)(1) and (B)(1) is not sufficient to start the motor, higher size sensing elements shall be permitted if the trip current does not exceed ____% of the motor nameplate full-load current rating, when the motor is marked with a service factor of 1.12.

a) 100
b) 110
c) 125
d) 130

See answer and applicable Code reference

The correct answer is: d) 130

Article 430 covers the requirements for motors, motor circuits and controllers. Part III of this Article focuses on motor and branch-circuit overload protection requirements. As noted in Sec. 430.32(C), motors marked with a service factor 1.15 or greater can use a sensing element with a trip current rating of up to 140% of the motor nameplate full-load current rating. The same holds true for motors with a marked temperature rise 40°C or less. All other motors are limited to 130%.

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.