What this RCBO is and where it fits
The Siemens 5SU1354-4KK25 is a 2-pole SENTRON RCBO — residual current circuit breaker with integral overcurrent protection — rated 25 A at 230/400 V AC, 50/60 Hz, with a 30 mA residual trip and Type F characteristic. The C-curve tripping characteristic (5–10× In) handles motor inrush and moderate inductive loads common in industrial control panels. Type F residual current detection covers AC sinusoidal, pulsating DC, and high-frequency AC components — the kind of leakage you get from VFD-fed motors, switched-mode supplies, and modern LED drivers. That makes this unit a better fit for mixed-load final subcircuits than a standard Type A RCBO. Snaps onto a standard DIN rail; 2 modular width units (36 mm) leave room for adjacent breakers. Depth of 77 mm (70 mm installation depth) fits most distribution boards.
Breaking capacity and thermal derating
Rated short-circuit breaking capacity is 10 kA per EN 60898 — sufficient for most residential and commercial final circuits where the prospective fault current stays under that threshold. Overvoltage category III and pollution degree 2 align with fixed-installation switchgear. The 25 A rating holds at 30 °C ambient. At 40 °C it derates to 23.5 A; at 50 °C to 21.75 A; at 60 °C to 20.25 A; at 70 °C to 18.25 A. If the panel ambient runs above 40 °C, factor the derating into your load schedule — the listed values are per the manufacturer's thermal curve.
Mounting and wiring notes
Mounting position is any — vertical, horizontal, or upside-down on the DIN rail. Supply feed can enter from top or bottom, which simplifies busbar routing in multi-row boards. Touch protection is built in (finger-safe terminals).