Clarifying Certifications for Manual Transfer Switch Equipment


When comparing NRTL Listings of different products, it is important to know what the appropriate UL standards are and how they apply to your specific application. You may not always be purchasing what you think you are. The most common UL Listings on emergency power connection equipment are as follows:

UL 1008 Transfer Switch Equipment

UL 1008 is specifically designed for transfer switch equipment. Products with a UL 1008 certification means the whole assembly is certified and has undergone rigorous testing to ensure performance, safety, and reliability. Non-Automatic transfer switches that are Listed under the UL 1008 standard are evaluated in accordance with Articles 517-Health Care Facilities, 702-Optional Standby Systems of the National Electrical Code (ANSI/NFPA 70) and the National Fire Protection Association Standard for Health Care Facilities (ANSI/NFPA 99). The inspection process is also easier when emergency power transfer switch equipment is UL 1008 Listed.

UL 1773 Termination Boxes

This standard is intended for applications that are hard-wired via terminals (usually permanent) and does not contain switching equipment or controls.

UL 98 Enclosed Dead-Front Switches

The UL 98 standard applies to double throw or knife edge switches (air switches), and does not allow the incorporation of circuit breakers. These devices are not Listed for the purpose of transfer switches and may not meet your project’s specifications.

UL 508/508A Industrial Control Equipment

This standard does not apply to transfer switch equipment. Instead it covers industrial control devices such as relays, contactors, motor starters, and programmable controllers.

UL 50 Enclosures for Electrical Equipment

A UL 50 Listing only certifies that the actual box is UL Listed for a specific environmental condition (Type 1, Type 3R, etc.). This does mean that the whole assembly (enclosure plus components) has undergone testing for the intended application.

With an ever-growing demand for safety, it is important to know the difference between the different UL certifications. More and more municipalities are requiring their manual transfer switches to be UL 1008 Listed to ensure safety and reduce liability. In order to uphold our commitment to provide our customers with safe, high-quality standby power equipment, our StormSwitch Manual Transfer Switches and TempTap Generator Docking Stations are UL 1008 Listed to ensure safe performance during times of need.

Photo Courtesy of David Goehring

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