What this MCCB is and what it protects
The Siemens 3VA1120-6EF36-0AG0 is a 3-pole molded case circuit breaker (MCCB) from the SENTRON line, rated for 20 A continuous current and fitted with a TM240 thermal-magnetic overcurrent release — meaning the thermal trip element is fixed at 20 A and the magnetic short-circuit pickup is adjustable via the TM240 dial, covering the typical range for motor branch or feeder protection in distribution panels. Its interrupting capacity hits 220 kA at 240 V AC, 154 kA at 415 V, 121 kA at 440 V, and still holds 17 kA at 690 V — numbers that put it squarely in the high-fault-current class for industrial switchgear where upstream transformer capacity or parallel-feed sources drive available fault current well above 100 kA.
Thermal derating and panel fit
The breaker carries its full 20 A rating straight through to 50 °C ambient; above that it derates linearly to 18 A at 70 °C — a curve that matters when the MCCB shares a crowded enclosure with other heat sources, so verify the actual cabinet ambient if you are loading all three poles near the limit. Dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — the standard 3VA frame footprint, so it drops into a panel cut-out or DIN-rail adapter designed for the SENTRON 3VA family without re-drilling.