Blue Sea 4125 AC A-Series Circuit Breaker Lockout Slide

The Blue Sea 4125 AC A-Series Circuit Breaker Lockout Slide is a mechanical safety device designed to prevent dual AC power sources from operating simultaneously on a single electrical panel. This lockout slide ensures that only one double-pole AC circuit breaker can be activated at any given time, eliminating the critical risk of shore power and generator or inverter output being energized in parallel—a dangerous condition that can damage equipment and create fire hazards.

Engineered for universal compatibility, the Blue Sea 4125 lockout slide fits all World or A-Series and Rocker-style double-pole circuit breakers without requiring panel modification. The device mounts directly to existing circuit breaker mounting screw holes, and includes all necessary hardware. Its mechanical design enforces true single-source operation—when one breaker is engaged, the slide physically prevents the second breaker from closing. This passive safety approach requires no pilot circuit, electrical monitoring, or maintenance, making it reliable in marine, RV, off-grid power, and backup generation applications where power source isolation is non-negotiable.

The 4125 is specified by marine systems installers, RV electrical specialists, and backup power operators who demand failsafe source isolation. It addresses a fundamental electrical safety requirement where accidental dual-source energization can cascade into catastrophic failures—destroyed inverters, generator backfeed damage to shore power infrastructure, or arc events. At 2 by 1 by 7 inches and weighing just 0.1 pounds, the lockout slide adds negligible footprint while delivering absolute functional assurance that power sources cannot conflict.