Selective RCD for 5SL4 base units — 40 A, 300 mA, AC type
The Siemens 5SM2623-2 is a 2-pole selective RCD unit (residual current device) from the SENTRON family, designed as a plug-in accessory for the 5SL4 series of miniature circuit breakers. It carries a 40 A rated current at AC and a 300 mA rated fault current, with AC-type residual current detection — meaning it trips on sinusoidal AC earth faults only, not pulsating DC or smooth DC. The selective design (time-delayed) means it coordinates with downstream RCDs: on a fault, the downstream device trips first, keeping this unit and upstream circuits live for supply continuity. This is not a standalone RCD — it mounts onto a 5SL4 base unit (the evidence calls it a 'product variation for 5SL4'), so you order the 5SL4 MCB separately and snap the 5SM2623-2 onto it. The assembly occupies 2 modular width units on a DIN rail, and the supply can enter from top or bottom. Rated insulation voltage is 460 V, overvoltage category III, pollution degree 2 — standard for residential and commercial distribution boards.
Thermal derating and mounting
The 40 A rating holds at 40 °C; above that, derate stepwise to 32 A at 70 °C (ambient inside the enclosure). The mounting position is any orientation, and the IP20 rating applies when the distribution board is installed with connected conductors — so it's panel-internal, not for wet or dusty environments. Fastening is standard DIN-rail REG (regular) clip. Dimensions are 70 mm wide by 70 mm deep by 90 mm tall, with a 70 mm installation depth into the enclosure. The unit is not sealable and has no adjustable off-delay or adjustable fault current — the 300 mA trip level is fixed.