What it is and what it does
The Siemens 5SN6020-7CN is a SENTRON-series 1P+N miniature circuit breaker rated 20 A at AC with a C-curve trip characteristic and 6 kA breaking capacity per EN 60898. It switches both phase and neutral, with the neutral pole switching but not protecting — the overcurrent trip is on the phase side only. That 6 kA rating is the short-circuit capacity at 250 V AC, which covers most residential and light commercial distribution boards where the prospective fault current stays under that level. The C-curve means it trips between 5 and 10 times rated current, so it handles motor inrush and transformer energization without nuisance trips while still clearing hard faults fast.
Where it fits and how it mounts
This MCB occupies one modular width unit (18 mm) on a standard DIN rail, with a depth of 76 mm and an installation depth of 70 mm. It mounts in any position, which helps when you're packing a tight enclosure. The IP20 rating applies with conductors connected — fine inside a distribution board but not for wet locations. Pollution degree 2 and overvoltage category III are standard for fixed-installation residential and infrastructure panels.
Thermal derating and environmental limits
The 20 A rating holds at 30 °C ambient. At 40 °C it derates to 18.8 A, and at 45 °C to 18.2 A — so if your panel runs hot, size the upstream protection accordingly. The operating range spans -40 °C to 75 °C, which covers unheated utility rooms and outdoor enclosures in most climates. It's halogen-free and silicon-free, which matters for clean-room or corrosive-environment installs where outgassing can't be tolerated.