What it is and what it does
The Siemens 3VA1120-5ED42-0AA0 is a SENTRON molded case circuit breaker (MCCB) — a 4-pole, 20 A line-protection device with a TM210 thermal-magnetic overcurrent release. It is designed to sit in a main distribution panel or sub-feed, protecting cables and downstream switchgear against overload and short-circuit faults.
Interrupting capacity — the headline number
This MCCB delivers 187 kA breaking capacity at 240 V AC. At 415 V it still clears 121 kA, and at 440 V it holds 75.6 kA. Those are high-interrupting ratings for a 20 A frame — meaning it handles fault currents strong enough to weld a standard breaker shut. At 500 V and 690 V the rating drops to 17 kA, which still covers most industrial 480 V and 600 V class installations.
Thermal rating and derating
Rated 20 A continuous at 40 °C. The TM210 holds that full 20 A all the way up to 55 °C. At 60 °C it derates to 19 A, and stays at 19 A through 70 °C. That is a tight thermal curve — the breaker sheds only 1 A over a 30 °C rise. Means the panel builder can load it close to nameplate without chasing derate tables for every extra degree.
Physical fit and environment
Mounts on a DIN rail or panel-mount base. Width is 101.6 mm (4 in), depth is 70 mm, height is 130 mm. The front face carries IP40 protection — splash-resistant from the front, but not sealed against hose-down. Inside a typical IP54 or IP65 enclosure it is fine. Operating temperature range is -25 °C to 70 °C.