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UL 857 Ed. 14-2025

Busways - Published Date: September 10, 2025

1.1 This Standard applies to service-entrance, feeder, and branch-circuit busways and associated fittings rated at 1000 V or less, 6000 A or less, and intended for use in accordance with the Canadian Electrical Code, Part I (CE Code, Part I), NFPA 70®, National Electrical Code® (NEC®), and the Mexican Standard for Electrical Installations (Utility), NOM-001-SEDE. These requirements do not apply to metal enclosed bus intended for connecting switchgear assemblies for use in prefabricated electric distribution systems.  NFPA 70®, National Electrical Code®, and NEC® are registered trademarks of the National Fire Protection Association, Quincy, MA.  1.2 For the purpose of these requirements, a busway is considered to be a grounded metal enclosure containing factory-mounted conductors that are usually copper or aluminum bars, rods, or tubes.  1.3 Requirements stated throughout this Standard for fittings apply to tap boxes, feed boxes, plug-in devices, and similar fittings, but do not apply to busway elbows, tees, and crosses.

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