Tech Talk 101: Understanding the UL 891 Switchboard Standard


Two engineers working on a switchboard


UL 891 is one of the most common standards that govern switchboard design, manufacturing and testing. Learn what this standard consists of and why it’s worth paying attention to if you’re outfitting your facility with low-voltage switchboards.

Want to learn more about switchboards and how they compare to switchgear? Check  out our e-book, The Complete Guide to Switchgear.

What is UL 891?

UL 891 is a standard developed by UL Solutions (previously Underwriter Laboratories), a global safety certification company. This standard specifically addresses requirements for low-voltage switchboards (those rated for 600V or less) intended for use in accordance with the National Electrical Code, Canadian Electrical Code and/or ANSI/NFPA 70.

What does UL 891 cover?

UL 891 involves a host of criteria switchboards must meet related to areas such as safety, materials, performance and design. (Note that the following is just an overview of what UL 891 requires. Manufacturers must purchase and review the current standard from UL Solutions for exact specifications.)


There’s plenty of room for manufacturers to create their own unique switchboard designs, but they should all adhere to some basic principles included in UL 891. For example, this standard specifies best practices for:

  • Switchboard enclosures
  • Spacing of components
  • Ease of access
  • Component-to-component compatibility
  • Compatibility with the electrical system


UL 891 specifies safety measures that all switchboards should include, such as emergency disconnects and protections against faults and arc flashes. Circuit breakers and fuses should swiftly detect and isolate electrical faults before they have a chance to cause damage or lead to an electrical fire. The standard also specifies how manufacturers must label components and document clear operating and maintenance procedures that protect personnel’s safety.


The materials used in switchboard construction must support its safe and efficient operation. This means sticking to materials that offer: 

  • Low flammability to minimize the risk of fire hazards
  • Electrical insulation with high dielectric strength to prevent short circuits and electrical shocks
  • Mechanical strength to withstand normal operating conditions
  • Resistance to environmental factors such as heat and moisture


UL 891 includes performance standards that switchboards must meet to ensure safe, seamless operation and long-term durability. These standards typically specify how various components of the switchboard should operate at normal conditions and during temporary surges or faults. Switchboards undergo rigorous testing to ensure they meet these performance standards.

How does a switchboard achieve UL 891 certification?

A UL 891 switchboard (one that is “UL Listed”) has undergone several steps:

  • Product development that complies with UL 891 standards
  • Rigorous testing to evaluate the system’s performance and safety under various conditions, such as overloads, short circuits and environmental factors
  • Possible factory inspection from UL to verify that the manufacturing facilities, processes and quality control procedures comply with UL standards and regulations

If a switchboard meets all UL requirements, UL Solutions issues a certification mark or label indicating compliance with the 891 standard. This mark assures consumers, regulators and authorities that the switchboard has undergone testing and meets relevant safety and performance criteria.

Once certified, the manufacturer must maintain compliance with UL standards through regular audits, inspections, and quality control measures.

What’s the Difference Between “UL Listed” and “UL Recognized”?

You may see some different designations related to UL compliance, especially since UL currently has overlapping labeling systems in place with eventual plans to transition to a more unified enhanced certification mark

Two designations you may encounter when it comes to electrical gear are “UL Recognized” and “UL Listed.”

  • UL Recognized applies to components or subcomponents that are intended for use within a larger product.
  • UL Listed means a product (not just a component) is fully compliant with a certain UL standard and ready for the end user.


How do you purchase a UL 891 switchboard?

Ensuring a switchboard is UL 891 Listed is key to maintaining the safety and performance of your electrical system. Work with a partner who has undergone the certification process to ensure their products meet all aspects of the UL 891 standard.

(Note that UL Solutions specifies manufacturers are not allowed to promote that they are working on achieving UL certification. They can only reference the UL standard when they have officially achieved it.) 

PCX FLX-Power™ integrated switchboards are UL Listed and are tested in an ISO 9001:2015 manufacturing environment. Combining prefabrication and customizability, our switchboards deliver on design, safety, materials and performance—all while meeting an individual customer’s specific needs.

Learn more in our guide.

Want to learn more about electrical solutions and the standards that influence their design and manufacturing? From low-voltage switchboards to high-voltage switchgear, we cover it all in The Complete Guide to Switchgear. Download your copy!



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