UL 489 2019-04 PDF

Full title and description

UL 489 — Molded-Case Circuit Breakers, 2019-04 edition. This standard (published by Underwriters Laboratories) covers requirements, construction, performance, and marking for molded-case circuit breakers (MCCBs) intended for the protection of circuits and equipment from overloads and short circuits, including integral trip units and accessories. It specifies tests and evaluation criteria for safety and performance of low-voltage MCCBs used in North American installations.

Abstract

This standard sets safety and performance requirements for molded-case circuit breakers rated up to specified voltage and current limits, including requirements for insulation, interrupting capacity, trip characteristics, temperature rise, dielectric strength, mechanical and electrical endurance, and marking. The 2019-04 edition consolidates test methods and construction requirements to ensure reliable operation of MCCBs in commercial and industrial electrical distribution systems.

General information

• Status: Active publication as of the 2019-04 dated edition (check with publisher for any later revisions or amendments)
• Publication date: April 2019 (designated 2019-04)
• Publisher: Underwriters Laboratories (UL)
• ICS / categories: 29.120 (Electrical equipment), electrical safety standards, product safety
• Edition / version: 2019-04 edition (revision of prior UL 489 editions)
• Number of pages: Varies by published file—typically 60–120 pages depending on format and annexes

Scope

UL 489 applies to molded-case circuit breakers intended for use in branch-circuit and service entrance ratings for electrical systems within the scope of low-voltage distribution. It covers various types of MCCBs, including thermal-magnetic and electronic trip units, and defines the ratings, construction, performance tests, and marking required to demonstrate safe interruption and protective performance under specified fault and overload conditions. The standard does not cover miniature circuit breakers, low-voltage power circuit breakers covered by other standards, or products outside the defined voltage/current ratings.

Key topics and requirements

• Construction requirements for molded-case circuit breakers, enclosures, terminals, and trip mechanisms
• Electrical ratings: rated voltage, rated current, interrupting rating (AIC/ICU), and short-circuit withstand
• Trip characteristics and trip unit types (thermal-magnetic, electronic adjustable trips), including calibration and tolerance
• Dielectric tests, impulse withstand and insulation coordination
• Temperature-rise tests for current-carrying parts and components
• Mechanical and electrical endurance (operating cycles) and reliability testing
• Short-circuit and fault-clearing performance, including test procedures for interrupting capacity
• Marking, labeling, and instruction requirements for safe installation and use
• Accessory and auxiliary device compatibility and testing (shunt trips, undervoltage releases, interlocks)
• Environmental and material requirements such as resistance to corrosion, flame retardance, and tracking

Typical use and users

UL 489 is used by manufacturers of molded-case circuit breakers to design and certify products for sale in markets that require UL compliance. It is also used by safety engineers, test laboratories, electrical inspectors, specifying engineers, procurement teams, and facility maintenance personnel to ensure selected MCCBs meet recognized safety and performance criteria for building and industrial electrical distribution systems.

Related standards

Commonly referenced and related documents include other UL standards and industry standards covering circuit breakers, accessories, and installation practices (for example standards that address low-voltage power circuit breakers, miniature circuit breakers, and coordination with national electrical codes and installation standards). Users often consult applicable national electrical codes and product-specific UL guides for complete compliance and installation requirements.

Keywords

UL 489, molded-case circuit breaker, MCCB, circuit protection, interrupting rating, trip unit, thermal-magnetic, electronic trip, electrical safety, low-voltage distribution

FAQ

Q: What is this standard?

A: UL 489 is the Underwriters Laboratories standard that establishes safety, construction, and performance requirements for molded-case circuit breakers used in low-voltage electrical distribution.

Q: What does it cover?

A: It covers design and construction, electrical and mechanical performance tests, interrupting capacity, trip characteristics, temperature-rise limits, marking, and accessory compatibility for molded-case circuit breakers within its defined voltage and current ratings.

Q: Who typically uses it?

A: Manufacturers, test laboratories, safety and design engineers, electrical inspectors, specifying consultants, and facilities maintenance and procurement professionals use UL 489 to design, test, specify, and verify MCCBs for safe operation.

Q: Is it current or superseded?

A: The document described is the 2019-04 edition. To confirm whether it remains current or has been superseded or amended, check with the publisher or the latest UL publication listings.

Q: Is it part of a series?

A: UL 489 is part of UL's family of product safety standards addressing circuit breakers and electrical protection devices; related UL and industry standards address other breaker types, accessories, and installation practices, forming a broader compliance framework.

Q: What are the key keywords?

A: Molded-case circuit breaker, MCCB, circuit protection, interrupting capacity, trip unit, electrical safety, UL 489.