80 A MCCB with 121 kA interrupting capacity — selectivity headroom for distribution
The Siemens 3VA1180-4EF32-0KC0 is a SENTRON molded case circuit breaker (MCCB) rated for 80 A continuous current at 40 °C, with a thermal-magnetic TM240 release. It carries a 121 kA breaking capacity at 240 V — that's the fault current it can safely interrupt without welding contacts or cascading upstream. At 415 V it still holds 75.6 kA, and at 690 V it's 11.9 kA. That kind of headroom means this breaker can sit close to a large transformer or generator bus and still coordinate with downstream feeders. Three poles, line protection version — no ground-fault module, no communication board, no undervoltage release. The only auxiliary is the shunt trip (STL) plus two HQ auxiliary switches (3VA9688-0BL33 integrated). It's a straightforward distribution breaker sized for a 80 A feeder in a panel that needs high fault-interrupt capability. The TM240 thermal-magnetic trip unit gives fixed thermal and magnetic settings — no electronic adjustability, which simplifies replacement but locks the curve.
Thermal derating and panel integration
The 80 A rating holds flat from 40 °C to 50 °C — no derating needed in a typical 40 °C panel. Above that it drops: 76.8 A at 55 °C, 75.2 A at 60 °C, 73.6 A at 65 °C, 72 A at 70 °C. If your enclosure runs hot (sunlit rooftop, next to a drive cabinet), size the load at the 70 °C figure. The breaker itself is 130 mm tall, 76.2 mm wide, 70 mm deep — standard SENTRON 3VA footprint. IP40 on the front, so it's protected against tool entry but not washdown; keep it inside a sealed enclosure in wet areas. Mechanical endurance is rated at 15 000 operations — that's the no-load cycle life. For a distribution breaker that cycles a few times a year, it's fine. For frequent switching (like a welding line or a compressor that cycles daily), consider a contactor upstream and leave the MCCB as backup protection only.