What it is and what the ratings mean
The Siemens 5SU1654-1RC25 is a SENTRON-series residual-current circuit breaker with overcurrent protection (RCBO) — a single device that combines a 25 A miniature circuit breaker (MCB) with a 30 mA residual-current device (RCD) in one 2-module-wide package. The C characteristic means it trips on overcurrent at 5 to 10 times rated current, which suits it for circuits with moderate inrush, like lighting banks, small motor loads, or general socket outlets in commercial and residential distribution boards. The 30 mA residual-current element is Type AC, meaning it detects sinusoidal AC fault currents only — the standard choice for basic shock protection in circuits without non-sinusoidal or pulsating DC fault profiles. The 1P+N design (one protected pole plus a switched neutral) fits single-phase final circuits where the neutral is switched with the line. Breaking capacity is rated at 10 kA per EN 60898 (the standard for household and similar installations) and 20 kA per IEC 60947-2 (the industrial standard for low-voltage switchgear). The higher 20 kA figure gives headroom for industrial panels where prospective fault current may exceed 10 kA; the 10 kA rating is what a residential final-distribution board typically requires. The part carries Overvoltage Category III and Pollution Degree 2, confirming it is designed for fixed-installation use within a distribution board.
Mounting and integration
Occupies 2 modular width units (36 mm) on a DIN rail. Depth is 70 mm, height 90 mm. Supply can enter from the top or bottom. The IP20 rating applies only when the distribution board is installed and conductors are connected — this is normal for a panel-mount device; it is not rated for standalone outdoor or washdown use. Rated for 50 Hz supply only, 240 V AC. Ambient operating range from -40 °C to 75 °C, with max 95% humidity. Mounting position is unrestricted. Energy Limitation Class 3 means it limits let-through energy effectively for downstream equipment protection.