Code Change Summary: A new informational note added to 400.1 addresses power supply cords.

In the 2017 NEC^®, a long-standing misinterpretation of the code was put to rest. Before the code change, some thought that power supply cords used as part of a listed power supply unit were exempt from the requirements in Article 400.

A new informational note was added to the scope of Article 400 to make it clear that cord sets and power supply cords that are constructed using flexible cord or cable listed in Article 400 are in fact subject to the rules in Article 400.

NEC Table 400.4 shows all of the different flexible cord and cable types covered in Article 400. Most electronic power supplies have a flexible cord that plugs into a receptacle. Some manufacturers of electronic power-supplies use flexible cords of a type listed in Table 400.4 when they construct their power supply units.

For example, Type SPT-2 is a flexible cord commonly used for power supply units and it also happens to be listed in NEC^® Table 400.4. Just because an electronic power supply may be listed by a nationally recognized testing lab doesn’t mean that the flexible cord it comes with is exempt from the uses permitted and uses not permitted in NEC^® sections 400.10 and 400.12.

Below is a preview of Article 400. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC^® edition of NFPA 70.