80 A, 30 mA, 400 V — the ratings that decide fit
The Siemens 5SM1347-0 is a 4-pole residual current operated circuit breaker (RCCB) from the SENTRON 5SM1 series, rated 80 A at 400 V AC with a 30 mA trip threshold. The 30 mA sensitivity is the standard for personal protection against direct contact — it's what you spec for general-purpose socket circuits and wet-area final subcircuits where the code calls for 30 mA RCD protection. The 80 A frame covers the main incomer for a small distribution board or a heavy submain; at 45 °C ambient it holds the full 80 A, and the derating curve is published stepwise down to 64 A at 70 °C, so you can size the upstream protective device knowing exactly where the RCCB thermally limits. Type AC means it detects sinusoidal AC residual currents only — not pulsed DC or smooth DC. That's fine for most residential and light commercial panels where the loads are linear AC, but if you have VFDs, UPSs, or LED drivers on the downstream side, the residual waveform can be pulsed or DC, and a type A or type B RCCB would be needed instead. The 10 kA short-circuit current rating (SCCR) and 70 000 A²·s I²t withstand tell you it survives a fault up to that level without rupturing, provided the upstream breaker clears within the energy limit.
Panel integration — DIN rail, 4 MW, top or bottom feed
Snaps onto DIN rail (REG profile), occupies 4 width units at 55 mm installation depth. The supply can enter from top or bottom — no mandatory orientation — and the mounting position is any, so it fits tight enclosures where the busbar arrangement forces a bottom-feed layout. Terminal capacity accepts 1.5 to 25 mm² solid or stranded copper; tighten to 2.5–3 N·m. The IP20 rating applies only when the distribution board is installed and conductors are connected — it's not a standalone IP20 device; the enclosure provides the environmental seal.