MCCB for line protection — 20 A continuous, 121 kA interrupting
The Siemens SENTRON 3VA1120-4EF36-0AE0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection — meaning it guards feeder circuits against overload and short-circuit, not motor or generator duty. Its TM240 thermal-magnetic release is fixed at 20 A and holds that rating from 40 °C through 55 °C; at 60 °C it derates to 19 A, and stays at 19 A up to 70 °C. Short-circuit breaking capacity reaches 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. That 121 kA figure at 240 V is the highest in the 3VA1 family — this breaker clears a fault fast enough to protect downstream gear even on high-capacity transformers. Rated insulation voltage is 800 V, and the breaker dissipates 12 W maximum under full load — useful to know for enclosure thermal budgeting.
Panel fit — 76.2 mm wide, 70 mm deep, 130 mm tall
The 3VA1120-4EF36-0AE0 occupies a 76.2 mm wide footprint on the DIN rail or mounting plate, with a depth of 70 mm and height of 130 mm. That 70 mm depth is shallow enough to clear most standard gland plates and backpanel wiring troughs without protruding into the wiring channel. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The 12 W power loss is conducted through the base and terminals — no fan required in a ventilated enclosure at 20 A continuous.