What it is and what the ratings mean
The Siemens SENTRON 5SV5444-0 is a 4-pole residual current operated circuit breaker (RCCB), Type AC, rated 40 A with a 100 mA trip threshold at 230/400 V AC, 50 Hz. The 100 mA sensitivity means it's sized for equipment protection or fire-prevention circuits rather than personal shock protection (which typically calls for 30 mA or lower). The 6 kA short-circuit current rating (SCCR) tells you it can safely interrupt a fault up to that level without welding contacts or cascading damage upstream — enough for most distribution boards behind a 63 A service fuse.
Panel fit and mounting
Snaps onto DIN rail (REG) per, occupies 4 modular width units (72 mm wide, 90 mm tall, 70 mm deep). Supply can land top or bottom — no forced orientation. IP20 with conductors connected and the distribution board installed; that's standard for enclosed panel gear, not for open washdown areas. Ambient range -25 °C to +45 °C operating, with storage extremes of -40 °C to +75 °C. The 4-pole form factor handles three-phase plus neutral in one unit — no separate neutral bar needed downstream.
Fault handling and endurance
Rated conditional short-circuit current per IEC 61008-1 is 0.5 kA in series with a backup fuse; the 6 kA SCCR applies when the device clears the fault alone. Let-through current is limited to 5 200 A, and the permissible I²t value is 58 000 A²·s — useful figures for checking selectivity with downstream MCBs. Mechanical life is 2 000 switching cycles, which is typical for an RCCB that sees infrequent manual test operations rather than daily load switching. Overvoltage category III, so it's rated for fixed-installation distribution boards, not for plug-in portable gear.