What it is and what it does
The Siemens 5SY7220-7 is a 2-pole miniature circuit breaker from the SENTRON series, rated 20 A at AC with a C-curve tripping characteristic — meaning it holds through brief inrush (motor starts, capacitor banks) and trips fast on hard shorts. It carries a 15 kA breaking capacity per EN 60898 and 25 kA per IEC 60947-2, so it handles fault currents up to that level without welding contacts or cascading upstream.
Panel fit and mounting
Snaps onto DIN rail via the quick-assembly system, any mounting position. Width is 36 mm (2 modular units), depth 76 mm, height 90 mm. Installation depth 70 mm leaves room behind the gland plate. IP20 with connected conductors — fine inside a closed panel, not for wet locations.
Temperature derating and environment
Rated 20 A at 35 °C; derates to 18.78 A at 40 °C, 16.08 A at 60 °C. Ambient range -40 to 75 °C, with humidity limits: 95% up to 55 °C, 55% up to 70 °C, 35% at 75 °C. Halogen-free and silicon-free construction — no outgassing concerns in sealed enclosures or near sensitive optics.