What it is and what it does
The Siemens 5SY8325-7 is a 3-pole miniature circuit breaker from the SENTRON family, designed for branch-circuit protection in industrial control panels and distribution boards. Its C characteristic (tripping between 5 and 10 times rated current) suits it for motor-starting and moderate inrush loads where a B curve would nuisance-trip. Rated 400 V AC with a breaking capacity of 30 kA per IEC 60947-2, it handles high-fault-current scenarios common in industrial mains. For DC circuits it's rated 60 V with 15 kA interrupting capacity, and under UL 1077 it carries a 5 kA rating — that's the number to use for North American supplemental protection listings. The 3-module-width body (54 mm wide, 76 mm deep, 90 mm tall) snaps onto DIN rail via the quick-assembly system. Installation depth is 70 mm.
What the ratings mean for your panel
Pollution degree 3 and overvoltage category III mean this breaker is rated for the harsh environment inside an industrial enclosure — conductive dust, condensation, and transient surges from upstream distribution. It's not a residential-grade device. The IP20 rating (with connected conductors) is standard for panel-mounted breakers; the finger-safe terminals are covered once wires are landed. Sealable terminals let you lock out adjustment after commissioning — useful for machines that must meet lockout/tagout procedures. Halogen-free and silicon-free construction matters if this breaker lives in a clean room or near sensitive electronics — outgassing from a fire won't corrode contacts or optics. Rated for 10 000 mechanical operating cycles — that's the life of the mechanism, not the electrical endurance under fault. For a panel that sees frequent switching (like a machine tool with daily power-down), that's a solid service life.
Compliance and documentation
Listed to IEC / EN 60947-2 and UL 1077 / CSA C22.2 No.235. The UL 1077 listing is supplemental protection — not a branch-circuit rated breaker under UL 489, so verify your local code's requirement before specifying it as the sole overcurrent device on a feeder. Vibration resistance tested to IEC 60068-2-6: ±1 mm at 5 to 25 Hz, 50 m/s² at 25 to 150 Hz. That covers most industrial machinery vibration profiles — pumps, compressors, conveyors. Temperature influence data shows derating above 55 °C: max 95% humidity at 55 °C, dropping to 55% at 70 °C and 35% at 75 °C. If your panel ambient runs hot, factor that into the load calculation.