Siemens 5SY8150-7 SENTRON MCB — 50 A C-Curve, 25 kA Breaking Capacity
The UL 1077 / CSA C22.2 No. 235 rating drops to 5 kA, so if the panel carries a UL label, verify the available fault current at the point of installation stays within that limit. The quick-assembly fastening system means it clips in and out without tools — useful when you're populating a multi-row panel and need to swap a failed unit without disturbing adjacent wiring.
Thermal Derating and Environmental Fit
Rated 50 A at 45 °C ambient, the 5SY8150-7 derates to 48.75 A at 50 °C and 47.45 A at 55 °C. The breaker is rated for ambient operation from -40 °C to 75 °C, with humidity influence capped at 95% up to 55 °C, then dropping to 35% at 75 °C. That's a wide environmental envelope; it handles outdoor shelters and unheated warehouses without condensation issues.
Fault Current Ratings Across Standards
Three breaking capacity ratings cover the common certification paths: 25 kA at 440 V AC per IEC 60947-2 (the main industrial standard), 15 kA at DC per the same standard, and 5 kA per UL 1077 / CSA C22.2 No. 235. The DC rating matters for control circuits or battery-backed distribution where the fault profile differs from AC.