5SY4 Miniature Circuit Breakers Siemens 5SY4 Miniature Circuit Breakers provide safe short-circuit and overload protection for industrial applications. Siemens 5SY Miniature Circuit Breakers are available in 1-, 2-, 3-, 4-, 1+N, and 3+N-pole versions and are designed for rated currents from 0.3A to 80A at rated switching capacities of 6kA, 10kA, and 15kA. 5SY4 protects circuits of air-conditioning and ventilation systems, control cabinets, and controllers from the consequences of short-circuit and overload events.