Line protection MCCB — 20 A, 121 kA interrupting capacity
The Siemens SENTRON 3VA1120-4EF32-0AB0 is a 3-pole molded case circuit breaker rated for line protection duty, carrying a continuous current Iu of 20 A and a rated insulation voltage Ui of 800 V. Its TM240 thermal-magnetic release provides fixed overload and short-circuit protection without an auxiliary release or undervoltage release fitted. The interrupting capacity reaches 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V — figures that govern its fault-clearing capability at the panel's available fault current. Rated current holds at 20 A up to 50 °C ambient, then derates linearly to 18 A at 70 °C. That means a panel running at 55 °C can only load this breaker to 19.2 A continuous; at 65 °C, 18.4 A. The operating temperature range spans -25 °C to 70 °C, with storage from -40 °C to 80 °C. Two HP auxiliary switches are built in, but there is no trip indicator, no communication function, no phase failure detection, and no ground fault monitoring — this is a straightforward thermal-magnetic breaker for basic feeder or branch protection in a distribution panel.
Panel fit and mounting
The 3VA1120-4EF32-0AB0 measures 76.2 mm wide, 130 mm high, and 70 mm deep. It mounts on a DIN rail or screws directly into the enclosure backplate. Front protection is IP40 — suitable for dry indoor panels; not rated for washdown or outdoor exposure. The 3-pole footprint matches standard SENTRON 3VA cutouts, so a panel laid out for a 3VA1110 frame accepts this breaker without rewiring.