The Siemens 5SL4215-8 is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, 2 poles, and a 1.6 A rated current. It's designed for residential and infrastructure panelboards where high inrush currents — motor starts, transformer energization, discharge lamps — would nuisance-trip a B or C curve. The D curve holds through a 10–20× rated-current surge, so it clears only on a hard fault, not a normal load transient. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, which means it safely interrupts a fault up to that level without welding the contacts or cascading upstream. That's the standard residential/commercial SCCR for this class; if your available fault current exceeds 10 kA, you need a current-limiting upstream device or a higher-rated frame.
D curve and derating — what the ratings mean for fit
The D characteristic (tripping between 10× and 20× In) is the key selection parameter here. At 1.6 A, that means the magnetic trip fires between 16 A and 32 A — enough headroom for a small motor or a bank of LED drivers without nuisance trips. But the thermal element still protects the downstream cable at the continuous rating. Temperature derating is real on this part. The 1.6 A rating holds at 30 °C; at 40 °C it drops to 1.54 A, at 45 °C to 1.5 A, and at 55 °C to 1.43 A. If the panel ambient runs hot — say, a crowded enclosure near a boiler or drive cabinet — size the load to the derated figure, not the nameplate. The MCB is rated for ambient up to 55 °C with 95% humidity, so it's fine in a damp basement or outdoor-rated enclosure as long as the IP20 (with connected conductors) is respected. Multi-phase operation is rated at 400/440 V AC; single-phase supply voltage is 400 V AC. The DC rating maxes at 72 V, so this is an AC-primary breaker — don't spec it for a DC distribution bus above that. Overvoltage category III and pollution degree 2 confirm it's suitable for fixed-installation panels with transient overvoltages (like lightning-induced spikes on a building feed).
Mechanical and panel fit
The 5SL4215-8 snaps onto a standard DIN rail (35 mm) and occupies 2 modular width units (36 mm total). Depth is 76 mm; installation depth is 70 mm — that's the space behind the panel face you need to clear for wiring and the arc chamber. Height is 90 mm. Mounting position is any, so you can lay it sideways in a shallow enclosure if the DIN rail is oriented horizontally. It's sealable (tamper-evident seal wire can be threaded through the housing), halogen-free and silicon-free — important for clean-room or corrosive-environment panels where outgassing matters. Touch protection is built in; neutral conductor switching is not included (this is a 2-pole breaker that switches both phase conductors but does not break the neutral — verify your circuit topology). Mechanical service life is 10 000 operating cycles typical — fine for a distribution breaker that sees infrequent manual switching. For a daily-switched load, consider a contactor or a dedicated switch-disconnector instead.