Who is UL and Why are Listings Necessary?

More commonly known by the abbreviation UL, Underwriters Laboratories tests and evaluates products to be certified and marked as either ‘UL Listed’ or ‘UL Recognized’, but what does it mean to have a UL stamp of approval and why does it matter to us? Today, we’re going to be taking a deep dive into the history of UL and gaining an understanding of the most used phrase in the NEC: “must be listed and approved”. Strap yourself in, because Here. We. Go. 

Typical UL listing on a product – Source: marks.ul.com

In The Beginning

Before the turn of the 20th century, William Henry Merrill, Jr. was sanctioned by the Boston Board of Fire Underwriters to assess the fire risk of the World Columbian Exchange, better known today as the World’s Fair. A graduate of MIT with a degree in electrical engineering, Merrill associated with different insurance underwriters during the course of the World’s Fair, at which he proposed his idea of an electrical testing laboratory. Two companies, The Chicago Underwriting Associates and The Western Insurance Union, took particular notice of Merrill’s idea and invested their support. With their financial succor, the Electrical Underwriters’ Bureau was founded.  

From the very beginning, William Merrill, Jr. had been focused on the safety of all. By standing on this merit, he attracted the attention of a well-known fire protection advocate and insurance agent Henry Clay Eddy. With the help of his newly named company president, founder and manager Merrill officially incorporated Underwriters Laboratories in Chicago in 1901.

From their first published safety standard, “Tin Clad Fire Doors”, to the most recent publication “Diversity and Inclusion Report”, UL has put forth the utmost energy to make the workplace not only more diverse and inclusive, but safer by providing testing on products to be used in every build. 

Why Does It Matter To Us?

If you were to open your code book to Annex A: Product Standards, you would find a comprehensive list of all the UL standards for the materials we use on a daily basis. Glancing through Chapter 3 in the NEC, we can go to any article on materials and the .6 of that article will say Listing Requirements, for example:

358.6 Listing Requirements. EMT, factory elbows, and associated fittings shall be listed.

It is up to the field technicians to know associated materials – examples would be that you cannot use a one-inch flex connector on a three-quarter-inch EMT, or an NM-B connector with FMC or LFNC raceways. That said, it is up to the manufacturer to design and have accessory products tested. The vigorous testing is not limited to only the installation materials such as cable assemblies, tubing and wireways, supports and straps, but also the fixtures, energy efficiency, environmental concerns, indoor air quality, performance and quality, reliability and durability, and safety.

UL issues the approval for products to be listed, and they can also assess and withdraw their stamp from a product. Many electricians are familiar with Federal Pacific panels and the fact that they are inherently unsafe, but what are the main issues with FedPac panels and breakers that ended with the removal of their UL listing?

UL listed control panel with both US and Canadian listings

Federal Pacific Scam

In 1949, the Federal Pacific Electric company patented their first circuit breaker, and in 1950 adopted the trademark Stab-Lok ®. Years later in 1979, FPE was sold and traded around from Reliance Electric, UV Industries, and finally landed with Exxon. In 1980, Exxon sued UV Industries for faking its UL endorsement. UL, in turn, then revoked FPE’s listing and safety approval. 

Although no recall was ever issued, the Consumer Product Safety Commission (CPSC) tested the FPE Stab-Lok ® circuit breakers and panels and found up to a 60 percent failure rate. Several companies have since started making UL-tested and approved replacement breakers in an attempt to make these panels, which are still being used in thousands of homes, a safer product for consumers that cannot afford a breaker panel change out. Some of these companies include American Circuit Breaker Corporation, Challenger Electric, Thomas and Betts, Connecticut Electric, and Unique Breakers Inc.

For more on the Federal Pacific story, check out this video we did awhile back

Yet Another Failure

Another case of rejected breaker panels and equipment concerned the company Zinsco or Zinsco-Sylvania. The main issue with their panels was that the busbars to which the breakers attach were made out of aluminum, which does not fare well when faced with overheating. This overheating causes the busbar to corrode and in some cases actually melt, which causes a weakened connection between the busbar and breaker. In turn, this causes arcing which produces more heat, and destructive failure can occur. 

While there are replacement breakers on the market today, it is recommended that an entire panel swap be done to ensure the aluminum busbars are taken out of the service completely. 

What Does All This Mean

In conclusion, the existence of a safety regulation authority is essential to ensuring consumers are having the best and most inherently safe products installed. Typically, field techs don’t perform such extensive tests on equipment as UL and similar companies perform. There are, however, some things to look for when performing maintenance or service calls, to determine the safety of these products. If the entirety of a molded case circuit breaker is loose or wobbly from the busbar, the chances are it is no longer making a good connection and arcing is likely occurring. Be sure the circuit is off, and remove the breaker from the busbar. Check the attachment point on the breaker and bus for a darkening or ‘burnt’ spot, or worse even melted contacts. Another thing to notice is a discoloration of the actual busbar. This would indicate overheating on a specific circuit or, in rare conditions, the entire busbar. 

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