The Siemens 5SU1324-6FA40 is a 2-pole RCBO (residual current circuit breaker with overcurrent protection) from the SENTRON series, combining a 40 A B-curve MCB and a 30 mA Type A RCD in a single 3-module-width unit. It protects against overload, short-circuit, and earth leakage in one device — saving a DIN-rail position compared to separate MCB + RCD pairs. Rated 230/240 V AC at 50 Hz, it carries 40 A at 30 °C ambient, derating to 29.2 A at 70 °C — the full thermal curve is on record so you can size for warm enclosures without guessing. The Type A residual current element detects sinusoidal AC faults plus pulsating DC fault currents — the standard requirement for circuits feeding single-phase electronics, switched-mode power supplies, and appliances with rectifiers. A pure AC-sensitive RCD would miss those pulses.
Installation and compliance
Supply can enter from top or bottom, which simplifies panel wiring when busbars run at the top. IP20 with the distribution board installed and conductors connected — normal for an enclosed panel. Degree of pollution 2 covers normal indoor environments with occasional condensation.