What this RCCB is and what the ratings mean for fit
The Siemens SENTRON 5SM1354-6 is a 4-pole residual current circuit breaker (RCCB) from the 5SM1 design, rated 40 A at 45 °C ambient with a 30 mA Type A instantaneous trip characteristic — meaning it detects sinusoidal AC fault currents plus pulsating DC fault currents up to 1 kHz, which covers most modern electronic loads like VFDs, switched-mode supplies, and LED drivers that generate pulsed DC leakage. The 10 kA short-circuit current rating (SCCR) means this device safely interrupts fault currents up to that level without welding contacts or cascading damage upstream, provided the upstream overcurrent device is coordinated per IEC 60947-2. The 4-pole construction (3 phases + neutral) suits it for three-phase TN or TT systems up to 500 V AC line-to-line. The 30 mA trip threshold is the standard for personal protection against indirect contact in dry locations (IEC 60364-4-41). The thermal derating curve is explicit: 40 A at 40 °C and 45 °C, then 38.4 A at 50 °C, 36.8 A at 55 °C, 35.2 A at 60 °C, 33.6 A at 65 °C, and 32 A at 70 °C — so if your panel ambient runs above 45 °C, you need to down-rate the continuous load accordingly. The operating ambient range is -25 to +45 °C, with storage from -40 to +60 °C.
Panel integration and wiring
Mounts on DIN rail (REG profile) in any position — no orientation restrictions. Occupies 4 width units (about 72 mm) with a 55 mm installation depth. Screw terminals accept solid or stranded copper from 1.5 to 25 mm²; tighten to 2.5–3 N·m. Supply can enter from top or bottom. IP20 protection applies when installed in a distribution board with connected conductors. Overvoltage category III — suitable for fixed installation downstream of the service entrance. Finger and back-of-hand safe touch protection built in.