The words “listed” and “labeled” are repeated often in the National Electrical Code (NEC), and refer to devices or appliances that are designed and manufactured in accordance with the requirements of a “listing agency,” also called a Nationally Recognized Testing Laboratory or NRTL.

    There are approximately fifteen certified listing agencies and, while they all follow the same standards when testing products, Underwriters Laboratory is the best known. When a product obtains UL approval, it is published in a list of ones that meet UL standards—which is what “listed” means.

    Once the product has been listed, the manufacturer is allowed to put a label on it with the logo of the listing agency, like the UL mark shown above, and specify the use for which it was manufactured, which makes it “listed and labeled.” The product shown above is labeled as a “current tap,” a technical name for a plug-in multiple outlet power strip. Other examples would be “domestic range” or “heat pump.”

    Because of the sterling reputation of nationally recognized listing agencies, any appliance or device that is listed and labeled will usually be quickly approved by the Authority Having Jurisdiction (AHJ), which is another name for the local building department. This is why manufacturers obtain listing and labeling for their electrical products.

    An important fact to remember is that the NEC code requires that a listed and labeled product be installed according the instructions in the product packaging, and the product is only approved for the use specified by the manufacturer (per NEC 110.3(B)). This means that the instructions on the box or in the enclosed installation manual effectively become part of the code.

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

• Which house appliances need a dedicated electrical circuit?

• Can a short circuit cause a high electric bill?

• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

• What causes copper wires to turn green or black in an electric panel?  

• What are the most common electrical defects found in a home inspection? 

• What is the life expectancy of electrical wiring in a house? 

• What is an "open junction box"? 

• How dangerous is old electrical wiring? 

• What is a ground wire? 

• I heard that aluminum wiring is bad. How do you check for aluminum wiring?  

• What is "knob and tube" wiring?  

• What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.