The Siemens 3RV1421-0HA15 is a SIRIUS circuit breaker for transformer protection, rated 0.8 A continuous. It provides phase failure detection and Trip Class 10. Breaking capacity is a flat 100 kA across the board — at 240 V, 400 V, 500 V, and 690 V AC — so it handles high-fault-current panels without cascading upstream breakers.
Sizing and application context
At 0.8 A continuous, this breaker is sized for small control transformers. The 7.25 W power loss in hot operating state means it dissipates heat. Maximum operating frequency is 15 operations per hour in AC-3 duty, so it's not intended for frequent switching — it's a protection device, not a contactor. The auxiliary switch is transverse design and field-addable (product extension auxiliary switch is Yes). Terminals accept solid 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²), stranded 2x (1 to 2.5 mm²) and 2x (2.5 to 6 mm²). AWG for main contacts: 2x (14 to 10).