The Siemens 5SY8402-8 is a 4-pole miniature circuit breaker from the SENTRON 5SY8 series, rated 2 A at 400 V AC with a D tripping characteristic.
Breaking capacity — what the ratings actually mean for your panel
For DC circuits it's rated 15 kA per the same standard, and under UL 1077 / CSA C22.2 No. 235 it's listed at 5 kA. The UL figure is lower because that standard tests at a different fault profile; if your panel requires UL listing, the 5 kA is the number to coordinate with the upstream SCCR. The 70 kA IEC rating gives you headroom on most industrial distribution boards without needing a current-limiting upstream breaker.
Mounting and wiring — drops into a standard 4-MU DIN-rail slot
72 mm wide (4 width units), 90 mm tall, 76 mm deep with a 70 mm installation depth. Accepts solid or stranded conductors from 0.75 mm² up to 35 mm² at the screw terminals; torque to 2.5–3.5 N·m. IP20 with conductors connected, so it's panel-internal only — no washdown exposure. Terminal comb available top and bottom for daisy-chaining phases. Mounting position any, ambient -25 to +55 °C, storage -40 to +75 °C.