Author(s): Derek Vigstol. Published on February 8, 2021.

In Compliance | NEC

Understanding the what, when, and why about NEC listing requirements


Does electrical equipment need to be listed? This is a question that stakeholders have approached NFPA with recently, and it’s one that comes up on a regular basis. In today’s world, where communication is dominated by social media and online forum discussions, people are having an increasingly difficult time determining what is required to be listed and what is not.

Specifically, the most common bit of misinformation floating around online is that everything must be listed to be installed. There have also been statements made about how listed equipment can be used in all sorts of ways, based on the assumption that a listed product is a safe product.

At the heart of these misconceptions exists an important question: What does it really mean for something to be “listed”?

Article 100 of NFPA 70®National Electrical Code® (NEC®), defines listing as “equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose.”

In other words, this equipment has been evaluated by a third-party agency that the AHJ trusts, and has been stamped as being able to safely do what the product is supposed to do. This third-party then publishes a list that includes the product in question, and the AHJ can use this information to help decide whether to approve an installation.

This is beneficial in several ways when it comes to electrical installations. Listing lets the AHJ know that the product meets the applicable industry consensus product standard, or that the evaluation body has physically taken the product, or a representative sample, and tested it to make sure it is safe to use as advertised. This is what makes section 110.3(B) so important. This section requires that listed equipment be installed and used in accordance with the instructions provided with the listing. One example of where this comes into play is in wiring method fittings. A fitting, such as a coupling or connector, gets a listing from a third-party organization because it performs as advertised with the wiring method system it is designed for. Using this fitting with a different wiring method type might physically work, but the fittings have not been evaluated to work with the other wiring method—meaning it may or may not operate safely. There is no way to know without testing it, and the AHJ can no longer use the listing to judge compliance.

Being listed to an industry consensus product standard also allows the NEC to require that only products that have met these standards be installed, if a product is required to be listed. In addition to the benefit for judging compliance, this allows standardization of products across manufacturers. Using the example of wiring methods, if a particular method and its associated fittings are required to be listed, then we know those components will work together, regardless if the fittings are from a different manufacturer as the wiring method.

This can also be a safety measure, and appliances are a great example. Section 422.6 requires that any appliance with a supply of 50V or more be listed if it is to be installed in a jurisdiction covered by the NEC. This keeps these appliances built to basic standards that incorporate certain safety requirements such as the type of conductor insulation that can be used, and ensuring there are important grounding and bonding connections in place. This becomes increasingly important considering that many appliance installations are not necessarily inspected by an AHJ—homeowners, for example, are unlikely to pull a permit and schedule an inspection when they replace a range. Having the appliance listed helps ensure that it will at least be built to a given standard.

Although the NEC doesn’t require that all electrical equipment be listed, it is important that we understand the importance for why certain equipment is required to be listed. Additionally, it is important that we understand the impact a listing has on how equipment can be installed and used. If the equipment is intended to be listed, the NEC will specifically state a listing requirement. Understanding the what, when, and why about NEC listing requirements helps us comply with important requirements for safety and keeps our world protected from electrical hazards. 

Derek Vigstol is an NFPA technical lead, Electrical Tech Services. NFPA members and AHJs can use the Technical Questions tab to post queries on NFPA 70 at