Code Change Summary: Revised code section now recognizes additional insulated conductor types.

During the 2017 NEC^® code cycle, insulated conductor types XHHN, XHWN, and XHWN-2 were added to Table 310.104(A) which provides a breakdown of conductor applications and insulation types. These new conductors can be summarized with the following wire designations from the UL Wire and Cable Marking and Application Guide:

• X = Cross-linked polymer insulation
• H = 75°C
• HH = 90°C
• N = Nylon jacket
• W = Moisture resistant

The only problem with adding the new wire types to the 2017 NEC^® was the fact that they should have also been added to Section 310.10. This section provides mandatory language on what types of conductors can be used in specific locations. It doesn’t really matter if Table 310.104(A) recognizes a wire type if Section 310.10 doesn’t allow it for use in dry, damp or wet locations.

In the 2020 NEC^®, these new wire types are now permitted to be used in specific locations shown in the code language below.

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 2020 NEC^® edition of NFPA 70.