C-curve trip and 0.5 A rating
The Siemens 5SJ4205-7HG42 is a 2-pole miniature circuit breaker from the SENTRON 5SJ4 series, with a C-curve trip characteristic and a rated current of 0.5 A at AC. At DC, the maximum rated voltage is 60 V, so it can serve DC control circuits or small solar combiner boxes within that limit. The breaker accepts both AC and DC voltage types, giving flexibility across mixed-supply panels.
The 36 mm width corresponds to 2 modular units (each 18 mm), so it occupies two slots in a distribution board. Protection class is IP20 with connected conductors, and IP40 in the handle range — adequate for enclosed distribution panels where the front handle is exposed but terminals are behind a cover.
Thermal derating and ambient range
Rated 0.5 A at 30 °C, 40 °C, and 45 °C, then derates to 0.48 A at 45 °C, 0.46 A at 50 °C, 0.44 A at 55 °C, and 0.42 A at 60 °C.