UL 1446

Standard for Systems of Insulating Materials - General

1.1 These requirements cover test procedures to be used in the evaluation of Class 120(E) or higher electrical insulation systems where the thermal factor is the dominating aging factor. These requirements also cover the investigation of the substitution of minor components of insulation in a previously evaluated insulation system and also the test procedures to be used in the evaluation of magnet wire coatings, magnet wires, and varnishes.

1.2 These requirements do not establish thermal ratings for/or alter established thermal ratings for individual components.

1.3 These requirements do not cover insulation systems exposed to radiation or operating in oils, refrigerants, soaps, or other media that potentially degrade insulating materials.

1.4 When any performance aspect of an end-product requirement is not covered by this standard, the applicable standard shall be used.

1.5 These requirements do not cover electrical insulation systems where transient overvoltages or partial discharge are present. Such electrical insulation systems shall be evaluated to the appropriate standard for the application. Such standards include, but are not limited to, IEEE C57.12.60, IEEE Standard Test Procedure for Thermal Evaluation of Insulation Systems for Dry-Type Power and Distribution Transformer, Including Open-Wound, Solid-Cast, and Resin-Encapsulated Transformers.


  • Edition Number: 6
  • Edition Date: 02/08/2007
  • Price Code: A
  • Type: ulstd
  • ANSI Approved: 03/21/2016
  • DOD Approved: