What this MCB does and where it fits
The Siemens SENTRON 5SL4120-7CC is a 1-pole miniature circuit breaker with C-curve tripping, rated 20 A at 30 °C and 400 V AC. Its 10 kA breaking capacity per EN 60898 means it safely interrupts short-circuit faults up to that level in residential and infrastructure branch circuits. The single modular width (18 mm) snaps onto standard DIN rail, and the C-curve (magnetic trip between 5 and 10 times In) handles moderate inrush from lighting, small motor loads, and control transformers without nuisance trips.
Temperature derating and real-world current
The 20 A rating holds at 30 °C ambient. At 40 °C the breaker must be derated to 18.48 A; at 50 °C to 16.82 A; at 55 °C to 15.92 A. For a cold-storage or freezer panel where ambient stays near -40 °C, the breaker runs cold and stays cold — no derating penalty, and the C-curve magnetic trip remains crisp. The wide operating range (-40 °C to 75 °C) covers both sub-zero and hot machine-cabinet environments.
Panel integration and physical fit
The breaker occupies one 18 mm modular width unit on DIN rail, with a total depth of 76 mm and an installation depth of 70 mm behind the panel. Mounting position is unrestricted. Rated IP20 with connected conductors — suitable for enclosed distribution boards. The sealable design allows lockout-tagout compliance. Halogen-free and silicon-free construction meets clean-room and food-processing material restrictions.