UL 857 PDF

1 Scope

1 1.1 This Standard applies to service-entrance, feeder, and branch-circuit busways and associated fittings rated at 600 V or less, 6 000 A or less, and intended for use in accordance with the Canadian Electrical Code, Part I (CE Code, Part I), the National Electrical Code (NEC), NFPA 70, and the Mexican Standard for Electrical Installations (Utility), NOM-001-SEDE, (see Annex B, Reference Item No. 1). These requirements do not apply to metal enclosed bus intended for connecting switchgear assemblies for use in prefabricated electric distribution systems.

1 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 1.3 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information.

1 1.4 Unless otherwise indicated, all voltage and current values mentioned in this Standard are root-mean-square (rms).

Summary of Topics

This revision of ANSI/UL 857 dated April 9, 2021 is being issued to update the title page to reflect the most recent designation as a Reaffirmed American National Standard (ANS). No technical changes have been made.

As noted in the Commitment for Amendments statement located on the back side of the title page, UL, CSA, and ANCE are committed to updating this harmonized standard jointly. However, the revision pages dated April 9, 2021 will not be jointly issued by UL, CSA, and ANCE as these revision pages only address UL ANSI approval dates.