Code Change Summary: Listing requirements were added to Article 440 for factory-assembled air-conditioning and refrigerating equipment and for field-installed electric heaters within those enclosures.

SME commentary: In the 2026 NEC^®, Section 440.2 now provides the following listing requirements for equipment covered by Article 440:

440.2(A) Factory-assembled electric motor-driven air-conditioning and refrigerating equipment shall be listed.

440.2(B) Electric heaters field installed within the enclosure of listed electric motor-driven air-conditioning equipment shall be identified as a listed field installable accessory as part of the listed equipment.

At the first draft stage, this proposal was rejected by Code-Making Panel 11 (CMP-11), which reasoned that listing requirements for HVAC equipment were better suited for mechanical codes such as the International Mechanical Code (IMC). However, during the second draft meetings, CMP-11 reconsidered and accepted the proposal after strong substantiation was presented showing that the NEC^® could not rely solely on external codes for this requirement. Many jurisdictions adopt the NEC^® without adopting a mechanical code at all. Additionally, in larger municipalities, inspectors often remain within their trade. An electrical inspector who only inspects electrical installations may have blinders on for other model codes and might not be aware of the code language in the IMC requiring product listing. Without a listing requirement within the NEC^® itself, unlisted air-conditioning and refrigerating equipment could be installed legally in some areas, leaving 110.3(B) difficult to enforce.

This new section also strengthens safety oversight for field-installed electric heat kits, which are sometimes the largest electrical load in a building. Misapplication of non-listed heater assemblies can lead to fires, particularly when third-party heater kits not evaluated with the original listed equipment are installed inside HVAC enclosures. The new requirement ensures that any field-installed heater is listed specifically as part of the equipment’s evaluated assembly.

The reasoning behind the suggested change also intended to address the growing use of flammable refrigerants required as a result of the EPA’s Significant New Alternatives Policy (SNAP) program. Modern refrigerants such as those classified under ASHRAE 34 introduce ignition hazards that are mitigated during product listing evaluations. Standards like UL 60335-2-40 (for air-conditioning equipment) and UL 60335-2-89 (for refrigerating equipment) take these additional hazards into consideration during the product testing and certification process to ensure compatibility and safety. Requiring that both the base equipment and any field-installed heat strips be listed ensures that all electrical components are evaluated together under the applicable product standard.

By placing the requirement directly in Article 440, the NEC^® now provides clear direction to installers, inspectors, and designers, removing ambiguity about where listing is required and how it applies to field-installed accessories.

This revision improves code clarity and aligns with 110.3(B) by making listing an explicit requirement for HVAC systems and any field-installed electric heaters within those systems. The result is greater uniformity across jurisdictions, enhanced fire safety, and consistent enforcement regardless of whether a mechanical code is adopted.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2026 NEC^® edition of NFPA 70.

2023 Code Language:

The code section did not exist

2026 Code Language:

N 440.2 Listing Requirements.

N (A) Listing Required. Factory-assembled electric motor-driven air-conditioning and refrigerating equipment shall be listed.

N (B) Field Installed Electric Heaters. Electric heaters field installed within the enclosure of listed electric motor-driven air-conditioning equipment shall be identified as a listed field installable accessory as part of the listed equipment.