Siemens 5SL4401-7 — 4-pole C-curve miniature circuit breaker, 1 A, 10 kA
Its breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, meaning it can safely interrupt fault currents up to 10,000 A under standard conditions — enough headroom for most residential and light commercial distribution boards without upstream fusing coordination headaches.
At 1 A, this MCB is sized for low-current circuits: control transformers, signal supplies, or lighting sub-circuits pulling under 1 A continuous. Rated operational voltage is 400 V AC for multi-phase operation, with a maximum of 440 V AC. Ambient temperature derating is already accounted for in the spec: at 40 °C the rated current drops to 0.95 A, at 45 °C to 0.92 A, and at 55 °C to 0.86 A. The MCB is rated for operation in up to 95% humidity at 55 °C.
Snap-on DIN rail mounting (any position) — standard 35 mm rail. Sealable with a lockable cover for tamper-proof isolation (sealable: yes). Halogen-free and silicon-free construction, so no corrosive off-gassing in sealed enclosures.