The Siemens 5SY3215-7 is a 2-pole miniature circuit breaker from the SENTRON 5SY3 series, rated 1.6 A with a C-curve tripping characteristic. That C-curve means it holds through mild inrush (5–10× rated current) and trips fast on a hard short — standard for general-purpose branch circuits feeding motor starters, contactor coils, or control transformers in a panel. The 400 V AC rating (overvoltage category III) covers the typical 400/230 V three-phase distribution bus. Breaking capacity sits at 4.5 kA per EN 60898 and 6 kA per IEC 60947-2; for UL 1077 / CSA C22.2 No. 235 installations it's rated 5 kA at AC. That's enough for most secondary distribution panels where the upstream transformer limits fault current below 6 kA. On the DC side it handles up to 72 V with a 15 kA interrupting rating per IEC 60947-2 — useful for control bus protection in the same enclosure. Mounting is snap-on DIN rail (quick assembly system), any position, and the 36 mm width (2 width units) takes two slots in a standard 18 mm/module rail. Terminal range accepts 0.75 to 35 mm² solid or stranded — big enough for a 6 mm² feed from the busbar and a 2.5 mm² downstream tap without pigtails. Combined terminals top and bottom mean you can land a busbar fork on the same clamp as the outgoing wire.
Sealable terminals allow the panel builder to lock the cover screws after commissioning, preventing casual tampering. Humidity tolerance is specified up to 95% at 55 °C, derating to 35% at 75 °C.