The Siemens 5SU1656-1KK40 is a SENTRON 5SU1 series RCBO — a combined residual-current circuit breaker and miniature circuit breaker in one 2-module (36 mm wide) package. It occupies a single DIN-rail position in a distribution board, rated for 40 A at AC with a C tripping characteristic and 6 kA breaking capacity per EN 60898. The 1P+N pole configuration means it switches the phase and monitors the neutral, tripping on AC fault currents only. For panel thermal planning: the unit dissipates up to 15.6 W at rated load, and current must be derated as ambient temperature rises — from 40 A at 30 °C down to 29.2 A at 70 °C. That derating curve is the one that governs real-world fill factor in a sealed enclosure.
Mounting and integration
Mounts on standard 35 mm DIN rail in any orientation. The 36 mm width (2 width units) and 70 mm installation depth fit standard SENTRON distribution boards. Terminal capacity accepts solid or stranded conductors from 0.75 mm² up to 35 mm² — sized for the full 40 A circuit without pigtailing. Supply can enter from top or bottom. IP20 rating applies only when installed in a distribution board with conductors connected — this is a panel-mount device, not a field-installed enclosure.