What it is and what it does
The Siemens 5SY6220-6 is a SENTRON miniature circuit breaker, 2-pole, rated 20 A at AC with a B tripping characteristic. It's built to protect branch circuits in industrial control panels, distribution boards, and machinery — the B curve means it trips between 3 and 5 times rated current, so it's a good fit for resistive or lightly inductive loads where you want fast clearing on a short circuit but don't need the inrush headroom of a C or D curve. It carries dual breaking-capacity ratings: 6 kA per EN 60898 for domestic-type installations, and 15 kA per IEC 60947-2 for industrial duty. That 15 kA figure is the one that matters in a panel with a high-fault transformer upstream — it tells you the breaker can clear a bolted fault without welding its contacts.
What the ratings mean for fit
The 20 A rating is at 35 °C ambient. At 40 °C it derates to 18.78 A, at 50 °C to 17.48 A — so if your panel runs hot, you need to account for that. The breaker is rated for overvoltage category III and pollution degree 3, which is typical for fixed-installation industrial panels. IP20 with connected conductors means it's not sealed against dust ingress, but the sealable option (yes) lets you lock the handle position for safety lockout/tagout.