© Xiaomin Wang | Dreamstime.com
Motors In Industrial Plant Maintenance And Repair

NEC: Motors — Part 9

Sept. 6, 2022
A disconnect location depends on whether it is for the controller or the motor.

Art. 430, Part IX requires a disconnecting means (disconnect) for separating motors and controllers from the circuit [430.101]. It also spells out requirements for meeting this requirement.

Where do you put the disconnect? The answer depends upon whether the disconnect is for the controller or the motor.

If it’s for the controller, it must be within sight of the controller location. However, there are three exceptions:

  1. The disconnect for motor circuits more than 1,000V also must be lockable. The controller must include a warning label stating where its disconnect is.
  2. You can use a single disconnect for a group of coordinated controllers (e.g., they drive several parts of a single machine).
  3. Disconnects for valve actuator motor assemblies don’t need to be in sight if you meet a couple of conditions stated in Exception No. 3.

If it’s a separate motor disconnect, it must be in sight of the motor and machinery location [430.102(B)(1)]. You can use a controller disconnect as the motor disconnect if said disconnect is in sight of the motor and machinery location [430.102(B)(2)]. However, there are a couple of exceptions in which you don’t need to comply with these requirements if you have a lockable controller disconnect:

  1. If the location is impractical or increases risk to people or property.
  2. It’s an industrial installation with written safety procedures and the conditions of maintenance and supervision ensure only qualified people service the equipment.

The disconnect must open all ungrounded conductors [430.103], have no independent pole(s), and plainly indicate whether it is in the on or off position [430.104]. At least one disconnect for a motor system must be readily accessible [430.107].

You must use one of the seven disconnect types specified in 430.109(A), unless otherwise permitted in 430.109(B) through (G) under the conditions specified. For example, you can use a motor circuit switch or a molded case circuit breaker [430.109(A)]. However, you are installing a 1/8 horsepower stationary motor, so in this case you can use the branch circuit overcurrent device [430.109(B)].

A disconnect for motor circuits at or under 1,000V (nominal) must be rated at 115% of the motor’s full-load current rating [430.110(A)]. However, for a torque motor, that changes to 115% of the motor’s nameplate current [430.110(B)]. What if you have more load than one motor? You’ll find rules for combination loads in 430.110(C).

A switch or circuit breaker can serve as both controller and disconnect, if it meets two conditions:

  1. It complies with the requirements of 430.111(A). For example, it opens all ungrounded conductors to the motor.
  2. It’s one of the types specified in 430.111(B)(1), (2), or (3). For example, an air brake switch.

Every motor and controller must include a disconnect [430.102(A) and (B)]. Each motor must be served by a single disconnect [430.112], but there’s an exception for group of motors under specific circumstances. You will also need more than one disconnect if there’s more than one source of electrical power to a motor [430.113].

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!