The Siemens 5SU1654-0KK32 is a SENTRON RCBO — a combined overcurrent and residual-current device in a single 2-module-wide (36 mm) package. It protects a 1P+N final circuit at 32 A rated current with B-curve magnetic tripping for short-circuit and overload, plus a 300 mA AC-type residual-current element that disconnects both line and neutral on a ground fault. The 10 kA breaking capacity (per EN 60898) means it can safely interrupt a fault current up to that level without welding contacts or rupturing the case — sized for residential and light commercial distribution boards where the prospective short-circuit current stays under that threshold.
What the ratings mean for fit
The 32 A rating is the continuous current at 30 °C ambient. Above that, the device derates: 30.4 A at 40 °C, 29.76 A at 45 °C, 28.8 A at 50 °C, 27.84 A at 55 °C, 27.2 A at 60 °C, 25.92 A at 65 °C, and 24.64 A at 70 °C. If the distribution board runs warm — say 50 °C inside the enclosure — the usable load drops to 28.8 A, not the nameplate 32 A. That derating curve is the one that governs real-world sizing, not the 30 °C headline figure. The 300 mA residual-current threshold is a delayed or selective-type trip level — not the 30 mA used for personal shock protection. This RCBO is intended for fire protection or equipment protection on circuits where a lower sensitivity would cause nuisance tripping from leakage in long cable runs or permanently connected equipment. The AC-type designation means it detects sinusoidal AC residual currents only; pulsed DC or smooth DC faults (common with VFDs, LED drivers, or EV chargers) will not trip it reliably. B-curve tripping means the magnetic release operates at 3 to 5 times rated current (96–160 A for this 32 A unit). That suits resistive and general-purpose loads — lighting, socket outlets, small appliances — where inrush is modest. For motor or transformer circuits with higher inrush, a C-curve (5–10× In) would be the correct choice; this B-curve will nuisance-trip on those loads. The 1P+N design switches the line conductor and disconnects the neutral on a residual fault, but the neutral pole is not protected against overcurrent — only the line pole has the thermal-magnetic element. That is standard for single-phase RCBOs in many territories, but worth noting if the local code expects both poles to be switched and protected.
Mounting and integration
Snaps onto standard 35 mm DIN rail. Two modular-width units (36 mm) occupy two adjacent slots in the distribution board. Supply can enter from top or bottom — no preferred orientation. Mounting position is any, so it can be installed horizontally or vertically without derating. Installation depth is 70 mm behind the panel face; overall depth with the front cover is 77 mm. IP20 rated once the distribution board is installed and conductors are connected — meaning finger-safe but not protected against water ingress.