The Siemens 5SM1647-0 is a SENTRON 5SM1-series residual current operated circuit breaker (RCCB), 4-pole, type AC, rated 80 A at 400 V AC with a 300 mA trip threshold. That 300 mA rating means it is sized for general fault protection — not supplementary personal shock protection (which typically calls for 30 mA) — so it is the right choice on submain or feeder circuits where equipment protection and fire prevention are the primary concern, not direct touch protection. Short-circuit withstand is 10 kA, and the unit is instantaneous-trip (no intentional short-time delay), so it clears fast — coordination with a downstream 30 mA RCCB or an MCB needs to account for that instant response.
Snaps onto DIN rail (REG) — standard 35 mm rail — and occupies 4 width units (roughly 72 mm). Installation depth is 55 mm.
Ambient and thermal derating
Rated for ambient temperatures from -5 °C to 45 °C (operating). Above 45 °C the continuous current must be derated: 76.8 A at 50 °C, 73.6 A at 55 °C, 70.4 A at 60 °C, 67.2 A at 65 °C, and 64 A at 70 °C. Storage range is wider: -40 °C to 60 °C.