UL 977

These requirements cover fused power-circuit devices to be employed in accordance with the National Electrical Code.

Fused power-circuit devices, as covered by these requirements, are considered to be either bolted pressure contact switches or high-pressure butt-type contact switches.

Bolted-pressure contact switches are devices in which the blade-jaw connections have an additional pressure or clamping action provided at both ends of the switch blades when the blades are in the fully closed position.

High-pressure butt-type contact switches are devices having butt-type contacts and a spring-charged mechanism.

These requirements do not apply to low-voltage AC power circuit protectors as covered by the Standard for Low Voltage AC Power Circuit Protectors Used in Enclosures, ANSI/IEEE C37.29, or to low-voltage AC integrally fused power circuit breakers as covered by the Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures, ANSI/IEEE C37.13.

Fused power-circuit devices may be manually or electrically operated and may incorporate electrical tripping means.