Question In the process of pulling THHN conductors through raceway we encountered some scuffing and scraping of the outer nylon conductor covering at the final fitting. The engineer says we ruined the conductor and wants it replaced. Does damage to the nylon covering constitute damage to the conductor insulation? Answer A Type THHN wire is comprised of three basic parts, the conductor, PVC insulation, and a nylon jacket. Each part has a specific use. Damage to the nylon jacket only, does not constitute damage to the insulation. The nylon jacket does provide mechanical protection to the insulation during and after installation and also provides gasoline and oil resistance for the wire. The question concerning replacement of the damaged wire can only be answered by visually examining the wire to understand the extent of the damage; and if the PVC insulation is damaged, or if the conductor is exposed to gas and oil, then replacing the wire may be necessary. UL certifies (Lists) THHN conductors under the product category Thermoplastic- Insulated Conductors (ZLGR), located on page 491 of the 2013 UL White Book and can also be found in UL’s Online Certification Directory at ul/database and enter ZLGR at the category code search field. THHN conductors that are certified (Listed) under (ZLGR) are evaluated for compliance with the Standard for Safety for Thermoplastic-Insulated Wires and Cables, UL 83. UL 83 requires THHN conductors to be provided with a nylon jacket extruded tightly over the insulation with a minimum thickness of 4 mils for 14-10 AWG conductors and thicker for larger conductors.
Posted on: Wed, 07 Jan 2015 05:11:27 +0000
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