80 A MCCB with 121 kA interrupting capacity — what that means for your panel
The Siemens 3VA1080-4ED42-0JH0 is a 4-pole SENTRON molded case circuit breaker rated 80 A continuous at 40 °C, with a maximum breaking capacity of 121 kA at 240 VAC — that's the short-circuit current it can safely interrupt without welding contacts or rupturing the case. At 415 V the rating drops to 75.6 kA, and at 690 V it holds at 11.9 kA, so the available fault current at your service voltage is the deciding factor for fit. This is a line-protection design, meaning it's configured for feeder and main breaker duty rather than motor branch-circuit protection. The 800 V rated insulation voltage gives headroom for 480 V and 600 V class systems. The breaker ships with a shunt trip release (STL) and a 2-auxiliary-switch plus 1-trip-alarm-switch HQ configuration. That means remote tripping and status feedback are built in — no separate accessory module needed for basic signalling. The shunt trip lets a safety PLC or E-stop circuit drop the breaker remotely; the auxiliary contacts report open/closed position to the control system.
Thermal derating and panel integration
Rated current holds at 80 A from 40 °C through 50 °C ambient, then derates to 78 A at 55 °C, 77 A at 60 °C, 75 A at 65 °C, and 74 A at 70 °C (–). If your enclosure runs warm — say a packed panel with drives or transformers — you lose 6 A by the time you hit 70 °C. The 19.2 W maximum power loss is the heat the breaker dumps into the enclosure at full load; factor that into your thermal budget. Dimensions are 101.6 mm wide, 130 mm high, 70 mm deep — standard SENTRON 3VA footprint, so it drops into existing panel cutouts and busbar systems without rework.