The Siemens SENTRON 5SU1354-7LB40 is a 2-pole RCBO (residual current circuit breaker with overcurrent protection) rated 40 A with a 30 mA residual trip threshold. It carries a Type A residual current characteristic for AC and pulsating DC fault currents, and a C tripping curve for the overcurrent element — meaning the magnetic release trips at 5 to 10 times rated current, typical for motor and lighting circuits with moderate inrush. The breaking capacity is 10 kA per EN 60898, which certifies its ability to safely interrupt fault currents up to that level in a 50/60 Hz network.
Ratings and derating
At 30 °C ambient the device carries the full 40 A. Derate linearly: 37.6 A at 40 °C, 36.4 A at 45 °C, 34.8 A at 50 °C, 32.4 A at 55 °C and 60 °C, 30.8 A at 65 °C, and 29.2 A at 70 °C. The thermal curve is the governing spec for panel placement — if the RCBO sits next to other heat sources in a crowded enclosure, use the 40 °C or 45 °C row as the design current, not the 30 °C headline.
Mounting and integration
Two modular width units (36 mm wide) snap onto a DIN rail. The 77 mm depth and 70 mm installation depth fit standard distribution boards. Mounting position is unrestricted — any orientation works. Supply can enter from top or bottom. Touch protection is built in. The IP20 rating applies once installed in a distribution board with conductors connected; the device itself is not rated for wet or dusty environments without an enclosure.