What this 3VA1120-5EF32-0KC0 is and what it does
The Siemens 3VA1120-5EF32-0KC0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. Its 187 kA interrupting capacity at 240 V means it can safely clear a fault of that magnitude without upstream devices needing to trip — critical for high-fault-current service entrances or transformer secondaries where the available short-circuit current is substantial. The 20 A continuous rating holds across 40 °C to 55 °C ambient, derating to 19 A at 60 °C and above, so in a warm enclosure you lose 1 A of headroom. Three poles, 800 V rated insulation voltage, and a shunt trip release (STL) built in — the shunt trip lets a remote signal (emergency stop, fire alarm, undervoltage relay) open the breaker electrically. Two HQ auxiliary switches provide status feedback to a PLC or indication lamp. The 12 W maximum power loss is the heat it dumps into the enclosure; factor that into your thermal budget if the panel is tightly packed.
Mounting and panel fit
The 3VA1120-5EF32-0KC0 measures 76.2 mm wide, 130 mm tall, and 70 mm deep. It mounts on a DIN rail or can be screw-fixed to a backplate. The 3-pole width is standard for a 20 A MCCB — it occupies one 3-module position on a 60 mm DIN rail. Leave clearance above and below for the arc-chute exhaust and for wiring the line and load terminals.