The Siemens SENTRON 5SM3318-0KK is a 2-pole residual current operated circuit breaker (RCCB), Type AC, rated 100 A with a 30 mA trip threshold on 230 V AC at 50 Hz. It's an instantaneous-trip device — no short-time delay — so it clears ground faults immediately, which is the standard choice for general-purpose protection in residential and light commercial distribution boards where nuisance tripping from transient leakage isn't a concern.
DIN-rail fit and panel integration
Snaps onto DIN rail (REG), occupies 2 modular width units (36 mm at 18 mm per MW), and installs at any orientation. Installation depth is 70 mm — measure your enclosure's clear space behind the rail before committing. Supply can land top or bottom, which helps when reworking an existing board without flipping the busbar. IP20 with conductors connected and distribution board installed — that's protected-finger touch only. Not rated for washdown or outdoor exposure; keep it inside a locked panel.
Breaking capacity and standard compliance
Rated short-circuit current (SCCR) is 10 kA per IEC 61008-1; the EN 60898 rating is 1 kA. The 10 kA figure governs fault-clearing capability at the device terminals — enough for most domestic and small commercial service entrances where the prospective fault current stays under that threshold. Overvoltage category III confirms it's rated for fixed-installation mains (distribution level, not sub-circuits).
Ambient limits and thermal derating
Operating ambient spans -5 °C to +45 °C; storage from -40 °C to +75 °C. The 45 °C ceiling is the running limit — above that you'd need to derate the 100 A continuous rating, though the datasheet doesn't publish a curve. If your panel internal temperature regularly hits 40 °C+ (sunlit enclosure, high-density gear), factor in headroom.