What It Is and What It Does
The Siemens 5SM2832-8 is a SENTRON residual current unit (RC unit) designed to pair with a 5SY series miniature circuit breaker, forming a combined RCD/MCB assembly for selective earth-fault protection in 400 V AC, 50 Hz distribution boards. Rated at 40 A with a 1000 mA trip threshold, the type A selective design detects sinusoidal AC and pulsating DC residual currents, and its selective (time-delayed) characteristic ensures coordination with downstream RCDs — only the faulted branch trips, keeping the rest of the installation live. The 3-pole unit snaps onto DIN rail (REG) and occupies 3 modular width units, with a 70 mm depth.
Selectivity and Coordination
The selective design (no short-term delayed switching) means this RC unit is intended as the upstream device in a graded RCD installation — it withstands transient earth faults and inrush without nuisance tripping, so only the downstream RCD clears a persistent fault. Rated surge current resistance of 5 kA and overvoltage category III suit it for fixed-installation panels where fault currents and switching transients are expected.
Mounting and Integration
Mounts in any position on DIN rail — no orientation restrictions. The supply can enter from top or bottom, which simplifies busbar routing in crowded enclosures. IP20 protection applies when installed in a distribution board with connected conductors — standard for enclosed panel use, not for wet or dusty environments. Silicon-free construction is a plus for automotive or electronics manufacturing lines where silicone outgassing can contaminate sensitive contacts or coatings.