The Siemens SENTRON 5SY6120-6CC is a 1-pole miniature circuit breaker (MCB) with a B tripping characteristic, rated 20 A at 35 °C and breaking 6 kA per EN 60898. Rated for 440 V AC single- or multi-phase, and 72 V DC maximum — the DC rating is low, so this is an AC-only choice for DC circuits above that.
Temperature derating — the real ampacity
The 20 A rating holds at 35 °C ambient. Above that, the 5SY6120-6CC derates linearly: 18.38 A at 40 °C, 17.5 A at 45 °C, 16.58 A at 50 °C, and 15.62 A at 55 °C. The surrounding temperature influence spec also caps humidity: 95 % up to 55 °C, dropping to 55 % at 70 °C and 35 % at 75 °C.
Snap-on quick assembly system, mountable in any position. Sealable, halogen-free, silicon-free — relevant for food, pharma, or clean-room builds where outgassing or tamper evidence matters.