What it is and what it does
The Siemens 3VA1220-4GF42-0JC0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the main disconnect and fault interrupter on a feeder or large load. It's a 4-pole unit rated a solid 200 A continuous (no derating needed up to 50 °C ambient, then it steps down to 176 A at 70 °C). The interrupting capacity is where this breaker earns its keep: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, 17 kA at 500 V, and 11.9 kA at 690 V. That's serious fault-clearing headroom for industrial distribution — it'll ride through a bolted fault on a 400 V bus without the upstream breaker having to back it up. It ships with a shunt trip (STL) release and two HQ auxiliary switches built in, so you can remote-trip it and get status feedback without adding accessory modules. Rated insulation voltage is 800 V, and the maximum power loss at rated load is 42 W — relevant for enclosure heat calculations.
Panel fit and integration
Footprint is 140 mm wide by 158 mm tall by 70 mm deep — that's a standard MCCB cutout for a 4-pole frame. It mounts on a DIN rail or directly to a backplate via the screw terminals. The 70 mm depth means it clears most 200 mm deep enclosures with room for wiring gutters.