The Siemens 5SY4550-5 is a SENTRON 5SY4 miniature circuit breaker rated 50 A at 230 V AC, 2-pole (1P+N) with tripping characteristic A. The 50 A rating means it protects a circuit drawing up to that continuous current — sized for a feeder or submain, not a final subcircuit. Mounts on a standard 36 mm DIN rail (2 width units) with a 90 mm height and 76 mm depth behind the panel — the 70 mm installation depth means it clears most gland plates and backplane wiring without extra standoffs.
Approvals include compliance with EN 60898 (domestic/light commercial) and IEC 60947-2 (industrial), plus UL 1077 and CSA C22.2 No. 235 with a 5 kA interrupting rating at AC.
Ambient temperature range -40 to +70 °C covers most indoor and outdoor enclosures; derate humidity per the curve: 95% RH up to 55 °C, then 55% up to 70 °C. The sealable feature (padlockable toggle) lets you lock the breaker in OFF position for lockout/tagout without an external hasp. Touch protection is built in (IP20 with conductors connected), meaning the busbar and terminal screws are shielded from accidental contact when the panel door is open.