What it is and what it does
The Siemens 5SL4203-7RC is a SENTRON miniature circuit breaker (MCB) — a 2-pole unit rated 3 A with a C trip characteristic, breaking 10 kA at 415 V AC per EN 60898. That C-curve means it trips between 5× and 10× rated current, so it handles moderate inrush from small motor loads or lighting ballasts without nuisance tripping, but still clears a hard short fast enough to protect downstream wiring. The 10 kA SCCR at 415 V is the standard residential/commercial distribution board rating — it interrupts fault currents up to that level without welding contacts or cascading upstream.
Panel fit and integration
Snaps onto standard DIN rail — 1 MW (18 mm wide) per pole, so this 2-pole unit takes exactly 18 mm of rail space. Depth is 76 mm; installation depth 70 mm, meaning the body clears a 70 mm deep enclosure back wall. Mounts in any position, which simplifies layout in crowded sub-distribution boards. IP20 with connected conductors — fine inside a closed panel, not for washdown zones.
What the ratings mean for the buyer
3 A at 30 °C and 3 A at AC — no temperature derating at 30 °C ambient, so the full 3 A is available in normal panel conditions. Overvoltage category III (distribution level) and pollution degree 2 (non-conductive dust only) mean it's rated for fixed-installation use in residential and infrastructure panels — not for industrial environments with conductive dust or high humidity. Halogen-free and silicon-free construction matters for clean-room or high-reliability installs where outgassing can contaminate contacts or optics.