UL508A Safety Standards for Motor Combination Starters

UL508A Safety Standards for Motor Combination Starters

Named for their construction and combined functions, motor combination starters are the most common type of packaged motor controller. They are used in applications that require a single control, responsible for starting and stopping the motor. Therefore, they are not ideal for applications that necessitate motor acceleration and speed control. Combination starters are simple to choose, install and use, eliminating the need to install and wire separate components.

In order to determine the safety of combination starters, the Underwriters Laboratories (UL) have issued UL508A standards for industrial applications and motor control. The UL is a global safety science company with more than 100 years of experience innovating safety solutions for both public and industrial applications and is one of a handful of companies approved to complete safety-related testing for OSHA. The UL specifies tests and verifications that components must pass before they can be listed as suitable for their intended functions.

UL508A standards for industrial motor control include requirements for industrial control panels. These specifications encompass all electrical components included in the building of industrial control panels such as circuit breakers and fuses, disconnects, motor controllers, overload relays, switches, pushbuttons and pilot lights. A UL508A certification verifies the safety and appropriate installation of all control panel components, control panel enclosures and sub-panels upon which components are mounted. Additionally, Part IV of UL508A defines the component functions, construction, testing and performance requirements for all combination motor starters. Certified combination starters meet the requirements set by NEC Article 430 for the motor disconnecting means, short-circuit and ground-fault protection, motor controllers and motor overload (OL) protection.

While the UL508A certification is sufficient for most normal industrial applications (i.e., panels for elevators, pumps, cranes and motors), it doesn’t cover the equipment and machinery that the panel controls. Additionally, the certification is limited to low voltage applications (panels supplied by 600VAC or below). For control panels and other equipment that operates in hazardous Motor Controllocations or flammable environments, other certifications are necessary.

As you start looking for a control panel for your industrial needs, be sure to choose the products and services of a UL508A-certified company. When you choose a company that adheres to UL standards, you will know that both the product and installation procedures of that company meet comprehensive safety standards. Your vendor should be able to verify this certification before you purchase any goods or services.

The figure to the right shows for the four component functions that compose a complete motor branch circuit as defined by the NEC.


Kaman has a number of value-added and engineering services divisions that can provide you with the UL508-certified products that you need. Those divisions include Kaman Automation, Control & Energy and Intellimotion.

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Pete Stollberger

One Reply to “UL508A Safety Standards for Motor Combination Starters”

  1. Steve says:

    Pete thanks for sharing this info. I used to share electric motors safety standards with many people & this piece of content on combination starters is wonderful.

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