Schneider Electric 9999-F4 Electrical Interlock

Schneider Electric's 9999-F4 Electrical Interlock is an external interlock kit in the Square D/Schneider Electric Class 9999 family, engineered to mount on a disconnect switch or circuit breaker and interrupt the separate control circuit whenever the main disconnect is opened. By breaking the control power as the handle moves to OFF, it helps prevent unintended re-energization and supports basic lockout/tagout practices in industrial switchgear. The interlock works with typical Class 9999 assemblies to coordinate the actuator and control circuit, enabling safer sequencing in panels and safety switches. Common applications include motor control centers, safety-switch installations, and control panels in manufacturing environments where the control circuit must be isolated before or during main switch operation. Within the broad Class 9999 lineup, interlock configurations span SPDT and DPDT designs, with examples such as 9999TC11 (SPDT) and 9999TC21 (2PDT) used on fused disconnects, and SPDT arrangements found in related kits for specific Square D enclosures like 8538/8738SE; these references illustrate the range of compatible interlock configurations that Schneider Electric supports for protective equipment. The 9999-F4 provides a compact, externally mounted solution intended to fit Schneider Electric’s disconnect and breaker families, helping installers meet safety standards while maintaining reliable interlock action across compatible switchgear.