The Siemens 5SY4205-7 is a 2-pole SENTRON miniature circuit breaker with a C-curve trip characteristic, rated 10 kA breaking capacity per EN 60898-1 and 35 kA per IEC 60947-2 at 400 V AC. That dual rating means it covers both residential-distribution board specs (EN) and industrial panel fault-current requirements (IEC) — the 35 kA figure is the one that matters when you're feeding a motor control center or a cement plant distribution board with a high prospective short-circuit current. The C-curve trips at 5 to 10 times rated current, so it's sized for motor and transformer inrush without nuisance tripping on a cold start.
Dust, heat, and vibration
Rated for ambient temperatures from -40 °C to 75 °C, so it lives in a hot control room next to a kiln or a cold unheated substation without derating drama. Vibration resistance per IEC 60068-2-6: ±1 mm at 5 to 25 Hz and 50 m/s² at 25 to 150 Hz — that's enough to survive on a vibrating conveyor panel or a crusher-plant wall. IP20 with connected conductors means it's sealed against finger contact but not dust ingress; mount it inside an enclosure that eats the dust and runs.
Panel fit and wiring
Width is 36 mm (2 modular units), depth 76 mm, height 90 mm. Snaps onto DIN rail via the quick assembly system — no tools needed. Mounting position any, so you can lay it sideways in a shallow gland plate if needed. Combined terminals top and bottom accept supply from either end; neutral conductor switching is not built in (this is a 2-pole breaker switching both phases, not a switched-neutral device). Pollution degree 3, overvoltage category III — rated for the heat, not the office.
DC and multi-phase capability
Rated 15 kA at DC per IEC 60947-2, so it can also serve DC distribution in a solar combiner or a battery bank. Multi-phase operation at 440 V AC matches 480 V delta systems common in North American industrial panels. Single-phase operation also at 440 V AC. Frequency range 50/60 Hz — standard line frequency, no derating needed.