Metal Roof Innovations Central

What is UL Listed?

Posted by Kimberly Reichert on Feb 21, 2019 8:33:31 AM

UL, an abbreviation for Underwriters Laboratories, is a testing and approving organization. Founded in 1894, UL performs safety testing on numerous electrical, mechanical, and chemical consumer and commercial products. Its roots began in electrical and fire safety, but UL now serves other industries and tests hazardous substances, water quality, food safety, and more.

S-5! ®UL Listed (Formerly Underwriters Laboratories) UL, an abbreviation for Underwriters Laboratories, is a testing and approving organization. You seem to see it everywhere – that red, black, or white circle with the capital “U” and “L” letters inside. It shows up on various products in our homes and workplaces. You rightly assume that it is important: When something has the UL stamp, it means it has been properly designed and engineered for its specific use. A UL listed mark on a product demonstrates it has been vigorously tested to meet safety specifications determined from the potential and probable hazards of the product. It means the product can be depended on to perform its purpose when needed the most.



When Was UL Founded?

UL is a safety organization. It was established in 1894 by William Henry Merrill as the Underwriters’ Electrical Bureau – which was a bureau of the National Board of Fire Underwriters. Throughout the 20th century, it was commonly known as Underwriters Laboratories.

S-5!® The Birth of

1893 Timeline Source:

Merrill was an electrical engineer in Boston who was often sent by underwriters to determine risk in fire insurance assessments. He increasingly saw the importance of testing building materials in order to determine the level of risk. Merrill soon began developing standards, testing, and building equipment. Seeing the need and importance for this type of testing, Merrill founded Underwriters Laboratories.

S-5!® UL Founded in 1894-

1894 Timeline Source:

S-5!® 1895 - William Henry Merrill and UL First

1895 Time Source:

S-5!® UL Labels

1906 Timeline Source:

The UL Listed Mark

UL stands for Underwriters Laboratories. The UL label was first introduced in 1906 to demonstrate that the product had passed testing. The company has transitioned to simply using the shortened UL as its name.

S-5!® UL and Renewable

1980 Timeline Source:

Why is a UL Listing So Important?

Underwriters Laboratories is a not-for-profit organization and gains no monetary benefit from product evaluation. This means that a UL mark is an indication of authentic product operation and safety. On the same note, if a UL product is tested again and fails testing, the UL listing is removed. UL also performs periodic inspections of the products they have previously Listed. Inspectors will visit the plant where the product is manufactured to make sure that the products being sold are actually the ones on the market.  

"UL Listed" versus "UL Recognized": What’s the difference?

These two labels may sound similar, but they are very different. "UL Listed" means a product has been tested by UL “to nationally recognized Safety Standards and has been found to be free from reasonably foreseeable risk of fire, electric shock and related hazards in a Division 2 environment”. "UL Recognized" is defined as “testing and evaluation of component products that are incomplete or restricted in performance capabilities.” UL Listed is harder to achieve because it follows industry and national standards.

UL Recognized is easier to attain because manufacturers can choose specific components for testing in specific assemblies – and not the complete fully-assembled product, category, or brand they manufacture. This has led to companies stretching the truth when it comes to their UL Listings. To say something is UL “Listed” when it is simply “Recognized”, makes for great advertising, albeit false, because it makes their products look just as safe as competitive products that legitimately carry a UL Listing. 

Such advertising claims rely on the consumer seeing the magic “UL” symbol and thinking that “all is good,” but not paying much attention to the different listing qualifications. It is deceptive advertising in that respect. UL strives to protect the consumer and specifically distinguishes between “UL Listed” and “UL Recognized” for this very reason.

S-5!® UL PV Photovoltaic

2008 Timeline Source:

Word De-Construction

Word of the Week: UL Listed


PRONUNCIATION: /juː /  |  /ɛl/  |  \ˈlist  |  əd/

PART OF SPEECH: Noun  |  U is the 21st letter of the alphabet  |  L is the 12th letter of the alphabet

SENTENCE: // Did you know that in many cases, the PVKIT™ 2.0 represents a savings of $6-$12 per unit and is sufficient to pay for the entire S-5-PV Direct Attachment solutions and clamp setup!

SYNONYMS AND RELATED WORDS: Underwriters Laboratories, UL, UL Listed, UL Certification Mark, William Henry Merrill, Electrical Bureau of the National Board of Fire Underwriters, UL Recognized

WHAT S-5! PRODUCTS ARE UL LISTED?: UL Standard 2703 - Mounting Systems, Mounting Devices, Clamping Devices and Ground Lugs for Use with Photovoltaic Modules and Panels

Models: S-5! PV KIT with roof clamp types S-5-U Mini, S-5- S Mini, S-5-T Mini, S-5-Z Mini, S-5-N Mini, S-5-E Mini, and S-5-N, S-5-U, S-5-S, S-5-T, S-5-Z, S-5-E, S-5-V, S-5-H90.

All of the above S-5! products are used to secure PV modules to metal roofing.

S-5!® Certificate of UL Listed Compliance-PV


UL protects the consumer. S-5! has the aforementioned products UL Listed under UL 2703. It is a bar standard for mounting systems before they can be installed. This safety standard for PV mounting systems fall into three major categories: Mechanical Loading; Grounding/Bonding; Fire Classification

Mechanical Loading

For S-5!, we are concerned with Mechanical Loading and assembly tests with modules and mounting systems. The tests are conducted with positive load, negative load, and parallel loading. In the case of S-5!, the connection between the module, PV MidGrab, PV EdgeGrab, Mounting disk, and PVKIT assembly to the clamp is investigated.


Specifically, the consumer should be aware that UL 2703 bonding/grounding listed racking systems are fully compliant with National Electrical Code (NEC) bonding/grounding requirements. The NEC in Article 250.4(A)(4) requires that any, "Normally non-current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path". 

The long and short of all of this is that, the S-5! clamp can be considered ‘”likely to become energized”. This is why it is included in the testing of UL 2703.

Fire Classification

Modules and mounting systems are tested in assembly with roofing to establish a Fire Classification A, B, or C. This is done to determine whether or not adding PV to a roofing system will adversely affect the fire classification of the roof. An important note is that roof attachments are not within the scope of UL 2703 – UL 2703 is intended for the rack up, not the rack down.  

In the end, the specific S-5! products that are UL Listed meet the national safety standard for their intended use.

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Tags: metal roof clamps, solar mounting, PV

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