The Siemens 5SM1614-6 is a 2-pole residual current circuit breaker (RCCB) from the SENTRON 5SM1 series, rated 40 A at 230 V AC with a 300 mA Type A residual tripping current. Type A means it detects sinusoidal AC fault currents plus pulsating DC fault currents — the standard for circuits feeding electronic loads like VFDs, switched-mode power supplies, and lighting ballasts that generate half-wave rectified leakage. Rated short-circuit current withstand is 10 kA, and the part carries a 1 kA surge current resistance. The 2-pole body takes 2 width units on DIN rail, with a 55 mm installation depth.
Thermal derating — the real ampacity
Full 40 A rating holds at ambient up to 45 °C. Above that, derate linearly: 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.