The Siemens 5SM2343-0 is a SENTRON RCD-unit (residual current device) designed for 4-pole AC circuits. It is rated 40 A at 50 Hz with a 30 mA fault trip threshold, AC residual current type, and instantaneous (non-time-delayed) response — meaning it trips immediately when leakage exceeds 30 mA, suitable for general shock protection in residential or commercial distribution boards. The unit occupies 3 modular width units (roughly 52.5 mm) on a DIN rail, with a depth of 70 mm and height of 90 mm. It mounts in any position and accepts top or bottom supply connections.
At 40 °C ambient the continuous rating is 37.2 A, dropping to 32 A at 70 °C. The 40 A nominal rating applies at the standard 30 °C reference; above that, follow the derating curve from the spec table to avoid nuisance tripping from thermal effects rather than actual leakage.
Rated insulation voltage is 460 V AC, surge voltage resistance 4 kV, overvoltage category III, pollution degree 2 — standard for fixed-installation distribution boards. The IP20 rating applies only when the distribution board is installed with connected conductors; the device itself is not sealed for wet environments. The unit is not sealable and has no adjustable trip threshold or OFF-delay. It is designed as a companion for the 5SL4 series MCBs (product variation noted for 5SL4).