I was told that I could not plug one extension cord into another on a construction site. The NEC does not seem to prohibit this practice. Where do I find such information?

Question: Extension cord daisy chaining

I was told that I could not plug one extension cord into another on a construction site. The NEC does not seem to prohibit this practice. Where do I find such information?

Answer

UL Lists what every one knows as “extension cords” as cord sets under the product category Cord Sets and Power Supply Cords (ELBZ), located on page 65 in the 2006 UL White Book or online at www.ul.com/database and enter ELBZ at the Category Code search. Cord sets and power supply cords are evaluated for compliance with the Standard for Safety for Cord Sets and Power Supply Cords, UL 817.

Plugging one cord set into another is what many refer to as “daisy chaining.” Daisy chaining increases the likelihood of misuse, excessive voltage drop and overloading the extension cord and may create a fire or shock hazard, therefore, UL 817 requires that cord sets be provided with a tag label that identifies the dos and don’ts of using an extension cord to avoid dangerous hazards. One of the markings required on that tag states, “Do not plug one extension cord into another.” So that, if one extension cord is plugged into another it is a violation of NEC 110.3(B) because the cord set would not be installed in accordance with the Listing installation markings.

About UL
UL helps create a better world by applying science to solve safety, security and sustainability challenges. We empower trust by enabling the safe adoption of innovative new products and technologies. Everyone at UL shares a passion to make the world a safer place. All of our work, from independent research and standards development, to testing and certification, to providing analytical and digital solutions, helps improve global well-being. Businesses, industries, governments, regulatory authorities and the public put their trust in us so they can make smarter decisions. To learn more, visit UL.com.