The Siemens 3RV1321-0BC10 is a SIRIUS circuit breaker designed for starter combinations — meaning it's sized to protect a motor branch circuit, not just a general distribution feeder. Its continuous current rating is 0.2 A, so it's for small motors or control transformers, not main power feeds. Finger-safe touch protection (IP20 on the front) keeps panel builders out of trouble during commissioning.
Mounting position is any orientation. Zero clearance needed at the sides or rear — 0 mm backwards, 0 mm at the side — so you can pack it tight in a panel without derating. Dimensions: 45 mm wide, 97 mm high, 96 mm deep. That 96 mm depth is the can-body length behind the panel; factor it into enclosure depth when the door closes.
The 0.2 A continuous rating is the key selector — this is not a general-purpose branch breaker. It's sized for a fractional-horsepower motor or a small control transformer primary. Operating frequency max is 15 operations per hour in AC-3 duty — fine for infrequent start/stop, not for a rapid-cycling application. Power dissipation is 5.5 W hot (1.8 W per pole), which matters for thermal management in a sealed enclosure. Terminal capacity: accepts 2x (1 to 2.5 mm²) solid or stranded, or 2x (2.5 to 6 mm²) — covers standard motor leads up to about 10 AWG. Shock rated at 25g for 11 ms, so it survives in a machine-mounted panel near a press or conveyor drive.