UL 1446 2020-11 PDF

Full title and description

St UL 1446 2020-11 — Standard for Systems of Insulating Materials — General. Provides requirements, test procedures and administrative rules for evaluating electrical insulation systems (EIS) used in motors, transformers, solenoids and similar electrotechnical devices, including thermal classification, chemical compatibility and system-level aging tests.

Abstract

UL 1446 establishes a framework and test program for assessing the combined performance of insulating materials when assembled as an electrical insulation system. The Standard defines EIS categories and thermal classes, identifies relevant specimen types and environmental stresses (thermal aging, moisture, mechanical stress, cold shock), and references established test methods (IEEE, IEC, ASTM) for determining temperature index/thermal class and the expected life of an insulation system. It is used to demonstrate system-level compatibility and to support product certification decisions.

General information

• Status: Active / Current recognition and application by UL Solutions and testing bodies.
• Publication date: November 2020 (2020-11) — published as St UL 1446 2020-11.
• Publisher: Underwriters Laboratories (UL) / UL Solutions.
• ICS / categories: Electrical engineering — Insulation systems / insulating materials (ICS 29.080.30; related 29.035 series).
• Edition / version: 2020 release (document reference 2020-11). Significant reorganizations and broader voltage scope were introduced in this revision.
• Number of pages: Document length varies by publisher/format (electronic/PDF distribution); see publisher distribution for exact page count.

Scope

UL 1446 covers the evaluation and recognition of Systems of Insulating Materials (EIS) used in electrical apparatus. The Standard applies to combinations of electrical insulating materials and their interaction when subjected to thermal aging and other stresses; it establishes procedures for assigning a thermal-class rating (temperature index / relative temperature index), for assessing chemical compatibility of add-on materials, and for system adoption or full system thermal-aging evaluation. The Standard is intended to support product safety and reliability assessments and to be used in conjunction with relevant end-product standards.

Key topics and requirements

• Definitions and classification of Electrical Insulation Systems (EIS) and Electrical Insulating Materials (EIM).
• Thermal classification procedures — determination of temperature index (TI) and relative temperature index (RTI) through full thermal-aging tests and comparative methods.
• Referenced test procedures and specimen types (e.g., IEEE 117, IEC 61857 series, ASTM D3145 Helical Coil tests, ASTM D2519 specimen preparation, ASTM/IEEE/IEC methods for electrical and mechanical retention checks).
• Chemical compatibility tests (sealed-tube and other procedures) for nonelectrical add-on materials.
• Environmental and mechanical stresses included in system evaluations: thermal aging cycles (high/medium/low), moisture exposure, vibration/mechanical stress, cold shock and end-of-life electrical stress tests.
• Administrative rules for system adoption (using an already-recognized EIS), system-specific testing, and marking/listing for EIS recognized by UL.
• Expanded application guidance — supports evaluation for devices operating well above traditional low-voltage limits (clarified in the 2020 revision).

Typical use and users

Used by motor, transformer and solenoid manufacturers; insulation material suppliers; test laboratories and certification bodies; design engineers validating thermal and chemical compatibility of insulation systems; and quality/compliance teams that must demonstrate system-level insulation reliability to regulators or market access bodies. UL Solutions and third-party labs perform testing and certification per UL 1446 for product acceptance.

Related standards

UL 1446 references and is used alongside multiple international test standards and methods, including IEEE 117 (random-wound systems), IEC 61857 (thermal endurance test methods), ASTM D3145 (Helical Coil tests), ASTM D2519 (specimen preparation) and various IEC/IEEE test procedures for electrical aging and partial-discharge evaluation. It also aligns conceptually with IEC insulation and thermal-endurance standards used for thermal-class assignment.

Keywords

electrical insulation system, EIS, insulating materials, thermal classification, temperature index (TI), relative temperature index (RTI), thermal aging, chemical compatibility, UL 1446, electrical safety, IEC 61857, IEEE 117, ASTM D3145.

FAQ

Q: What is this standard?

A: UL 1446 is the Standard for Systems of Insulating Materials — General; it sets out procedures and administrative rules for evaluating combinations of insulating materials as a complete insulation system for electrical equipment and assigning thermal-class ratings.

Q: What does it cover?

A: It covers definitions, specimen preparation, system-level thermal aging tests, chemical compatibility tests, environmental and mechanical stress procedures, and rules for system adoption and recognition. It references established IEEE, IEC and ASTM test methods for the technical procedures.

Q: Who typically uses it?

A: Motor, transformer and generator manufacturers, insulation material suppliers, independent testing laboratories and certification bodies, and design and compliance engineers who must demonstrate the thermal endurance and compatibility of insulation systems.

Q: Is it current or superseded?

A: The 2020-11 release (St UL 1446 2020-11) is the referenced version in this product page and is in active use; check UL Solutions or your national standards distributor for any amendments or later editions beyond 2020-11 before relying on it for compliance decisions.

Q: Is it part of a series?

A: UL 1446 functions as a general, system-level standard and references specific test standards (IEEE, IEC, ASTM) rather than forming a multi-part UL series; it is commonly used in conjunction with end-product safety standards and with international thermal-endurance standards.

Q: What are the key keywords?

A: electrical insulation system, EIS, thermal classification, temperature index, chemical compatibility, thermal aging, UL 1446, IEC 61857, IEEE 117, ASTM D3145.