Both UL 489 and UL 1077 are UL certification standards for circuit breakers. How to judge which standard is applicable to UL certification for circuit breakers is a matter of great concern to circuit breaker manufacturers. Next, Ankey Jie introduces the difference between UL 489 and UL 1077 certification for circuit breakers.
What are UL 489 and UL 1077?
UL 489 Circuit Breaker
UL 489 circuit breakers "are intended to be installed in circuit breaker enclosures or as part of other equipment, such as service entry equipment and switchboards." They are often required for panel design according to the National Electrical Code.
UL 1077 Auxiliary Protector
UL 1077 defines an auxiliary protector as a device used as overcurrent, overvoltage, or undervoltage protection in appliances or other electrical equipment that already provides or does not require branch overvoltage protection.
Important Note: Although the term circuit breaker is used to describe UL 489 and UL 1077 devices, UL 1077 devices are not considered circuit breakers by UL. They are defined as complementary protectors.
UL Standards Comparison-UL 489 vs. UL 1077
under UL service, low-voltage air circuit breakers, molded case circuit breakers and miniature circuit breakers are evaluated and "listed" as UL 489 and can be used as independent products.
In contrast, "approved" equipment under UL 1077 (supplementary protectors used in electrical equipment) is only evaluated for use as a component in a "listed" product.
UL 1077 supplemental protectors are "approved" components compared to "listed" circuit breakers. This means investigating their factory installation in "listed" products (such as UL 508a panels).
Both UL 489 and UL 1077 equipment must pass a series of calibration, overload, endurance and short circuit tests.
Structural differences
the main physical difference between UL 489 miniature circuit breakers and UL 1077 secondary protectors is the required pole spacing.
UL 489-1 inch air, 2 inches surface.
UL 1077-3/8 inch in air, 1/2 inch above surface.
When to use UL UL 489 and when to use UL 1077
the general rule is that a UL 489 circuit breaker can protect multiple devices at the same time, such as the entire control panel; while the UL 1077 auxiliary protector protects a device, except for those that supply power to the motor or transformer and those that exit the device. These will be classified as branch circuits, or can be used for egress or feeder utilization devices. In cases where UL 489 (branch) protection is not required or provided by other equipment, an auxiliary protector can be used. Circuit protectors listed in UL 489 can be used as final overcurrent devices dedicated to protecting branch circuits and outlets. It does not require the connection of additional spare overcurrent devices. Finally, UL 489 circuit breakers can be used instead of UL 1077 supplemental protection devices.
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