Siemens 5SU1354-7LB20 SENTRON RCBO — 20 A, Type A, 10 kA
The Siemens 5SU1354-7LB20 is a 2-pole (1P+N) residual current circuit breaker with overcurrent protection (RCBO) from the SENTRON 5SU1 series. It combines a 20 A thermal-magnetic overcurrent release (tripping characteristic C) with a Type A residual current device in a single 36 mm wide unit. The 10 kA breaking capacity per EN 60898 means it can safely interrupt fault currents up to that level on a 230/240 V AC supply, making it suitable for final circuits in residential and commercial distribution boards where both short-circuit and earth-fault protection are required in one device.
Ratings and what they mean for fit
The 20 A rated current (at 30 °C) with C-curve tripping is the standard choice for general-purpose socket-outlet circuits, lighting, and small appliances — the C curve allows brief inrush from motorised loads without nuisance tripping. The Type A RCD detects pulsating DC fault currents, which is essential for circuits supplying electronics, variable-speed drives, or appliances with rectifiers; Type A is the minimum requirement for most modern household and commercial installations. The 10 kA breaking capacity per EN 60898 certifies the device for use in installations where the prospective short-circuit current does not exceed 10 kA — common in distribution boards downstream of a main switch or upstream breaker.
Thermal derating and installation conditions
The 20 A rating applies at 30 °C ambient; derate progressively to 14.6 A at 70 °C (–). Mounting position is any, which simplifies panel layout. The device is 36 mm wide (2 width units) and 77 mm deep, with an installation depth of 70 mm. IP20 protection applies only when installed in a distribution board with connected conductors. The 5SU1 design accepts supply from either top or bottom.