Siemens 5SU1654-0KV20 RCBO, Type AC 300mA, B 20A, 10kA, 1+N

The Siemens 5SU1654-0KV20 is a combined residual current device and miniature circuit breaker (RCBO) — a single module that packs RCD and MCB protection into one 70 mm wide unit. It is a Type AC (wave shape) device, meaning it detects sinusoidal AC residual currents only. The 300 mA trip threshold suits it for fire protection or circuits where nuisance tripping from leakage is a concern, rather than direct personal shock protection (which typically demands 30 mA or lower). The overcurrent side is a 1+N-pole B-curve 20 A breaker, rated for 10 kA breaking capacity. B-curve trips between 3 and 5 times rated current — a good fit for resistive or general-purpose loads, light commercial lighting, or control transformers. The 10 kA short-circuit capacity at the device terminals means it can interrupt faults up to that level without upstream coordination issues, provided the prospective fault current at the panel does not exceed it. DIN-rail mounted; the 70 mm width occupies four standard 17.5 mm modular spaces.