The Siemens 3VA1120-5GF42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 20 A continuous current with a TM240 thermal-magnetic overcurrent release. It's a 4-pole unit configured for line protection — that's the main feeder or branch circuit, not a motor-protective function. The interrupting ratings climb to 187 kA at 240 V AC and still deliver 121 kA at 415 V, so it handles high-fault utility feeds without cascading upstream breakers.
Mounts on a DIN rail or panel-mount with the standard 4-pole width of 101.6 mm and a depth of 70 mm. The front face carries an IP40 rating — fine for a dry indoor panel, but not for washdown zones. The 12 W maximum power loss at full load means the enclosure's thermal budget needs to account for that heat, especially if you're stacking several breakers in a row.
Rated insulation voltage is 800 V AC, and the maximum DC operational voltage is 600 V — so it's usable on DC circuits up to that level, but the interrupting ratings listed are for AC. The adjustable short-circuit release (li) goes up to 320 A, giving some selectivity tuning for downstream feeders. The N-conductor is protected at 100%, meaning the neutral pole is fully rated, not just a switched neutral.