The Siemens SENTRON 5SM3314-3 is a 2-pole residual current circuit breaker (RCCB) rated for 40 A at 230 V AC, 50 Hz, with a 30 mA residual trip threshold. It's classified as Type F — designed to detect AC residual currents plus pulsating DC and high-frequency fault currents common on variable-speed drives and inverter-fed loads. The short-time delayed switching function gives it selectivity against transient surges, so nuisance tripping on motor start-ups or capacitor banks is less likely.
Thermal derating and conductor sizing
The 40 A rating holds at ambient temperatures up to 45 °C. Above that, it derates 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 (–). If your panel runs warm — say, near a transformer or in a non-ventilated enclosure — size the upstream breaker for the derated figure, not the nameplate 40 A. Terminal blocks accept solid or stranded conductors from 1 to 16 mm², with a tightening torque of 2.5 to 3 N·m. That covers most branch-circuit wiring up to 6 AWG.
Snaps onto standard DIN rail, occupies 2 width units, and installs 70 mm deep. Mounting position is unrestricted; supply can enter from top or bottom. Overvoltage category III means it's rated for fixed-installation distribution panels, not for plug-in equipment.