What you're looking at — and what the Z-curve means for your panel
The 5SL4304-0RC is a Siemens Betagard miniature circuit breaker — 3-pole, 4 A rated at AC, with a Z tripping characteristic. That Z-curve is the key spec: it trips between 2x and 3x In (8 to 12 A magnetic release), which is tighter than a B-curve and much tighter than C or D. Z-curve MCBs are built for semiconductor and control-circuit protection where you need short-circuit clearing without nuisance trips on small transformer inrush or capacitive loads, but still want fast reaction to a fault. At 415 V AC rated voltage, with a maximum of 440 V AC for multi-phase operation, it covers standard European 400 V three-phase distribution.
Panel fit and mounting — the 3-module width and derating reality
Mounting position is any — no orientation restrictions. Thermal derating is published: 4.5 A at 30 °C, 4.2 A at 40 °C, 4.1 A at 45 °C, 4 A at 50 °C, 3.9 A at 55 °C, 3.7 A at 60 °C. If your panel ambient runs 50 °C, you're at the nameplate 4 A — no headroom. At 60 °C you lose 0.3 A off the rating. That's the figure to use for continuous load sizing, not the 30 °C number.
DC rating and vibration — edge cases that matter
Maximum DC rated voltage is 72 V — useful if you're breaking a 48 V or 60 V control bus, but not rated for 110 V DC circuits.
Sourcing this order code
If you're filling a BOM line or replacing a failed unit in a live panel, send the order code and quantity for a firm quote.