The Siemens 3RV1421-0BA15 is a SIRIUS circuit breaker specifically designed for transformer protection. It carries a continuous current rating of 0.2 A and a Trip Class of CLASS 10, meaning it will trip within 10 seconds at 7.2× the rated current — a standard thermal-magnetic curve matched to inrush characteristics of small control transformers.
The interrupting rating holds at 100 kA across the full AC voltage range: 240 V, 400 V, 500 V, and 690 V. That is a flat high-fault curve — no derating as voltage climbs, which simplifies panel SCCR calculations when this breaker feeds a transformer primary. The auxiliary switch contacts are rated at 1 A at 24 V, 0.5 A at 230 V, and 0.15 A at 60 V — these are the make/break capacities for the signal circuit, not the main power path.
The 45 mm width (three module spaces) and 96 mm depth fit standard distribution panels. Mounting position is any orientation; no derating required for side-by-side placement — backwards and side clearances are both 0 mm. Solid conductor capacity is 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²); stranded accepts 2x (1... 2.5 mm²) and 2x (2.5... 6 mm²). AWG equivalents for main contacts are 2x (14... 10).
Substance prohibitance date of 01.05.2012 aligns with RoHS compliance scope. Phase failure detection is included; ground fault detection is not built in — that would require an external RCD or a separate 3RV ground-fault variant.