The Siemens 5SM3347-0 is a SENTRON RCCB (residual current circuit breaker) rated 80 A at 400 V AC, 50 Hz, with a 30 mA AC-type trip threshold. The 80 A rating is the continuous current-carrying capacity at 40 °C and 45 °C; above that the part derates linearly to 64 A at 70 °C — so in a warm panel or high-ambient enclosure, the real load limit is lower than the nameplate 80 A. The 30 mA trip is the standard for personnel protection (shock hazard) under IEC 60364, and AC-type means it detects sinusoidal residual currents only — not pulsed DC or smooth DC faults, so it's suited for circuits without rectifiers or VFDs downstream. The instantaneous design (no short-time delay) means it trips within a cycle on a residual fault, which is the right behaviour for personnel protection but means it cannot coordinate with downstream selective RCCBs in a multi-level distribution scheme.
The 77 mm overall depth includes the front projection. Mounting position is any — vertical, horizontal, or upside-down — which simplifies layout in tight enclosures. IP20 with the distribution board installed and conductors connected; that's typical for enclosed panelboards, not for open or wet locations. Finger and back-of-hand safe per the protection-against-electrical-shock rating, meaning the live terminals are recessed enough that a standard test finger cannot contact them when the part is mounted in a closed panel. Silicon-free construction matters for applications where silicone outgassing can contaminate contacts or optics (e.g., automotive paint lines or clean-room adjacent zones).
Thermal derating — the real-world load limit
At 50 °C it drops to 76.8 A, at 55 °C to 73.6 A, at 60 °C to 70.4 A, at 65 °C to 67.2 A, and at 70 °C to 64 A.
The 5SM3347-0 carries overvoltage category III (distribution-board level) and is designed to DIN EN 61346-2 and DIN EN 81346-2 (function designation F for protective device). The manufacturer provides standard compliance documentation including CE declaration of conformity and, for the SENTRON family, RoHS and REACH statements are available on request. The part is finger and back-of-hand safe and silicon-free.