The Siemens SENTRON 5SM2623-8 is a 2-pole selective residual current device (RCD-unit) rated for 40 A at 230 V AC, with a 300 mA rated fault current. It is designed to mount in distribution boards alongside 5SL4 miniature circuit breakers, occupying 2 modular width units on the DIN rail. The selective (type S) design means it delays tripping during short-duration earth faults, coordinating with downstream RCDs so only the faulted branch clears — critical for maintaining supply to essential circuits in a panel.
Rated at 40 A and 300 mA fault current, this unit protects a 230 V AC circuit against earth leakage while allowing normal load current up to 40 A. The selective characteristic (IΔn = 300 mA) provides a time delay so that downstream 30 mA RCDs trip first — the 5SM2623-8 only operates on sustained faults, preventing a nuisance blackout of the whole submain. Insulation voltage (Ui) is rated 460 V, and surge voltage resistance is 4 000 V, confirming it handles overvoltage Category III conditions typical of distribution panels.
Protection class is IP20 with conductors connected and the distribution board installed — standard for enclosed panel mounting. The unit is not sealable, so it is intended for accessible distribution boards where periodic testing is required.