Siemens 5SJ6304-7 — 3-pole C-curve MCB at 4 A, 6 kA
Rated 4 A at 400 V AC, this breaker protects a single-phase or three-phase load drawing up to roughly 2.8 kW (assuming a 0.9 power factor). The 6 kA breaking capacity is the same across the 5SJ6 range up to 63 A — no derating to worry about at this current level. For DC circuits, the maximum rated voltage is 60 V, so it works on 24 V or 48 V control buses but not on higher DC rails. The insulation voltage is 440 V AC, and the overvoltage category is 3, which covers fixed-installation distribution boards. The mechanical service life is 20 000 switching cycles typical — adequate for a panel that sees occasional manual isolation, not for daily load switching.
The 5SJ6304-7 snaps onto a 35 mm DIN rail and occupies 3 width units (roughly 52.5 mm). Installation depth is 70 mm, which fits standard shallow enclosures. The mounting position is unrestricted — horizontal, vertical, or flat — so it works in tight layouts. Protection class is IP20 with connected conductors, meaning the front terminals are finger-safe once wired.