Breaking capacity and thermal derating — what they mean for panel fit
The Siemens 3VM1180-4ED12-0AA0 is a SENTRON molded case circuit breaker (MCCB) in a single-pole form factor, rated 80 A at 40 °C. Its 76 kA breaking capacity at 240 V AC handles high-fault utility feeds common in North American 240/120 V split-phase panels; at 415 V AC the rating drops to 9 kA, which still clears most industrial fault levels in 400 V three-phase systems. The TM210 thermal-magnetic release provides LI (long-time and instantaneous) protection — the thermal element tracks overloads, the magnetic element trips on short-circuit. The adjustable instantaneous pickup maxes out at 800 A, per the datasheet.
Thermal derating curve — continuous current across ambient temperature
The breaker holds its full 80 A rating from 40 °C through 50 °C. Above that, the continuous current derates linearly: 78 A at 55 °C, 77 A at 60 °C, 75 A at 65 °C, and 74 A at 70 °C. If the panel ambient runs above 50 °C, the load current must be reduced accordingly — the 74 A ceiling at 70 °C is the hard limit, not a recommendation. Maximum power loss is 6 W.
Panel integration — footprint and environment
The breaker occupies a 25.4 mm wide (1 in) DIN-rail slot, 130 mm tall and 70 mm deep. Front-face protection is IP40 — suitable for enclosed panel mounting where tools or fingers cannot contact live parts. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. No auxiliary contacts are fitted as standard (zero CO contacts), and no motor drive or communication module is included on this variant.