Technical Article

UL Listed Devices For Industrial Automation

July 14, 2022 by Shawn Dietrich

UL Listed devices are certified as safe within North America, specifically, the US. Learn about the importance of UL Certification and the key role it plays in industrial automation.

UL Listed devices are deemed safe in North America

Figure 1. Devices such as switches, breakers, contactors, and controllers are UL Listed, which means they have been tested and deemed safe to sell in North America, specifically, in the US. Image provided by


Underwriters Laboratories (UL) Certification

A UL Listed or Certified instrument is a device or product that has been submitted to the UL to be tested under certain conditions which determine if the product is safe to sell in North America. The UL is a third-party laboratory that specializes in testing products to ensure they are safe for consumers. They perform tests ranging from but not limited to EMC, air quality, reliability and durability, safety, and wireless. Having your product UL Certified shows your customers that your product is safe to use within North America, and specifically, the United States of America. 

Just about every country has its own version of third-party testing companies which are nationally recognized. Canada uses the Canadian Standards Association (CSA) Listed but will accept UL Listed components. Europe uses Conformité Européenne (CE) Listed products with some countries accepting the UL European (UL EU) Mark. Any product that is listed with a nationally recognized laboratory will have an official mark that shows it has been fully tested and complies with the country's safety standards.


Is UL Listing Required?

Even though being UL Listed is not required, OSHA 1910.399 states that any electrical equipment to be installed must be accepted, certified, listed, or labeled by a nationally recognized testing laboratory. This means your device or equipment can be sold in America but not installed unless it meets the above criteria. Other countries have similar phrasing within their safety standards, such as the Electrical Safety Authority (ESA) in Ontario, Canada. 

These requirements are slightly vague, so you might find your local electrical building code to be more specific and require all devices to be UL or CSA Listed in order to be deemed safe for installation. Some facilities will have internal policies that dictate all electrical devices must be listed with specific testing laboratories. For equipment builders, this means they need to research the location and companies of their machine's final installation position to determine if the components need to be UL/CSA, or for Europe, CE Listed. 

There are some exceptions for devices that cannot be tested for various reasons; in this event you should consult OSHA and your electrical safety inspector. Ultimately, the final decision comes down to the electrical safety inspector to determine if your equipment is safe for installation.

For some situations, including many government and school applications (like a technical education lab setting) UL is strictly required and may be included as a requirement in a bid process. If a manufacturer chooses to sell products to this market, the UL Listed Mark will be necessary.


UL Listed products ensure worker safety
Figure 2. UL Listed products help to ensure worker safety, whether it’s electrical or safety equipment. Image used courtesy of Canva


UL Listed Products

Typically, UL Listed components are complete products that service the electrical industry such as electrical cabinets, computers, and electronics. These UL Listed products are entire packaged assemblies available to consumers and companies, such as your laptop power supply or a DIN mount miniature circuit breaker. Additionally, products that deal directly with safety also benefit from the UL or CSA Listed mark, such as life jackets, fall arrest harnesses, and safety shoes. Many companies require that any electrical component or safety product used within the facility be UL or CSA Listed. This ensures the safety of all the workers in the facility.

For companies such as integrators who do not directly manufacture end products, adherence to UL guidelines is often a characteristic that will differentiate competitors. For example, an electrical panel-building integrator will comply with UL 508A for Industrial Control Panels. This ensures that any assembly built by the shop will comply with UL guidelines, appropriate for installation in any location. 


UL Recognized Products

In the industrial automation sector, many electrical components are almost always found as part of a larger assembly and may not be a standalone piece of equipment. This could include a semiconductor power converter chip or a circuit board that exists inside that larger power supply assembly. Some common items in a control cabinet may even be UL Recognized, such as a wire crimp.

While these required UL Recognized marks are not as difficult to get as a UL Listed certification, there are extra installation measures for UL Recognized products to ensure they are not exposed to chemicals or liquids. 


UL Testing

Having a product UL Listed costs the manufacturer a significant amount and that cost is typically passed on to the customer. This increased cost can sometimes drive customers to purchase unlisted components at a reduced cost. Additionally, for some manufacturers, it is unrealistic to have every component off the assembly line be UL tested. For these reasons, UL grants facilities the option to test their own products and apply the UL stamp. This process requires the manufacturer to undergo quality and testing audits to ensure they are performing the tests as directed by UL. Being able to perform the UL testing within the same facility as the manufacturing saves time and money.    


Reconditioned Electrical Equipment

As equipment ages, components need to be replaced, and if this equipment was UL compliant, then the components within the equipment will be UL Listed and should be replaced with UL Listed components. In the event that the equipment was reconditioned, the UL mark may not be valid anymore. Recently the National Electrical Manufacturers Association (NEMA) released a policy on reconditioned electrical equipment. The policy covers what kinds of equipment can be reconditioned and which kinds cannot. By following this policy maintenance, staff can determine if the component or equipment can be rebuilt or reconditioned safely with the UL compliant mark still valid.