Product identity and function
The Siemens 5SU1324-1RC40 is a SENTRON-series residual current operated circuit-breaker with integral overcurrent protection (RCBO), rated at 40 A with a C tripping characteristic and 30 mA Type AC residual current detection. It is a 2-pole device occupying 4 modular width units (72 mm wide) for DIN-rail mounting in distribution boards.
Key ratings and their meaning for fit
The 40 A rated current at AC combined with the C characteristic means this RCBO is sized for circuits with moderate inrush — typically motor or lighting loads in commercial or industrial final subcircuits — where the magnetic trip threshold is 5 to 10 times rated current, avoiding nuisance trips on startup. The 30 mA residual current rating provides additional protection against earth faults, covering the standard threshold for personal protection against direct contact (per IEC 60364). Type AC detection means it responds to sinusoidal AC residual currents only — suitable for circuits without electronic loads generating pulsed or DC fault currents. Breaking capacity is rated at 10 kA per EN 60898 and 15 kA per IEC 60947-2. The higher IEC figure applies when the RCBO is used as a circuit-breaker in industrial distribution; the EN figure governs domestic/commercial installations. Both values confirm the device can interrupt fault currents up to those levels without external fusing, provided the prospective short-circuit current at the installation point does not exceed the lower of the two ratings.
Installation and environmental constraints
Mounting position is any, and the supply cord can enter from either top or bottom, giving flexibility in panel layout. The device is 72 mm wide (4 MW) and 70 mm deep, fitting standard DIN-rail enclosures. IP20 protection applies when the distribution board is installed with connected conductors — this is a finger-safe rating for enclosed panels, not for wet or dusty environments. Ambient temperature range spans -40 °C to +75 °C, covering most indoor and sheltered outdoor installations. Overvoltage category III and pollution degree 2 confirm suitability for fixed installations downstream of the main distribution board.