What it is and what it does
The Siemens SENTRON 5SU1324-6FR25 is a 2-pole RCBO — a combined overcurrent and residual-current device — rated 25 A at 30 °C, with a 30 mA Type A residual trip and B-curve overcurrent characteristic. It breaks fault currents up to 10 kA per EN 60898, which means it clears a hard short without upstream devices needing to trip. Insulation voltage is 500 V, and it withstands 4 kV surge impulses — enough for overvoltage category III in a standard distribution board.
Thermal derating — the real current you get
The 25 A rating holds at 30 °C ambient. At 40 °C it drops to 24 A, at 50 °C to 23 A, and at 60 °C to 22 A. If the panel runs warm — say a packed enclosure near a drive — use the 40 °C or 50 °C figure for your load calculation, not the 25 A headline. The device operates from -40 °C to 70 °C, so cold starts in unheated plant rooms are fine.
Mounting and integration
Two modular-width units (36 mm) on a DIN rail, 72 mm deep, 85 mm tall. Mounting position any, supply feed top or bottom. The IP20 rating applies only when the distribution board is installed with conductors connected — so it's not a standalone outdoor device. Pollution degree 3 means it's suited for industrial environments where conductive dust or condensation is possible. Touch protection is built in.