The Siemens SENTRON 5SM2825-8 is a 2-pole residual current unit (RC unit) designed to mount alongside a 5SY miniature circuit breaker, forming a combined RCD/MCB protective device. It is rated for 63 A operating current at 230/400 V AC, with a 1000 mA tripping residual current, and is classified as Type A selective — meaning it detects AC and pulsating DC fault currents and incorporates a short time delay to coordinate with downstream devices, preventing nuisance tripping on transient surges.
What the ratings mean for fit
The 63 A rated operating current sets the maximum continuous load this RC unit can carry — sized for a main incoming supply or a large sub-feed in a distribution board. The 1000 mA residual trip threshold is deliberately high: this is not for personal shock protection (which requires 30 mA), but for equipment protection against earth leakage currents that could cause fire or insulation degradation. The selective design means it withstands 5 kA surge current without tripping, so it sits upstream of standard RCDs and lets downstream units clear first — critical for maintaining supply to healthy circuits during a fault. Type A fault current sensitivity covers AC residual currents and pulsating DC — the kind produced by single-phase rectifiers in switched-mode power supplies, variable-speed drives, and LED drivers. If your panel feeds electronics or motor drives, Type A is the minimum; a standard AC-type RCD may not detect pulsating DC and could fail to trip.
Panel integration and mounting
Snaps onto DIN rail (REG) and occupies 2 width units — 71 mm wide — in a standard distribution board. Depth is 70 mm, installation depth also 70 mm, so it sits flush with the MCB it pairs with. Mounting position is any, which simplifies layout in tight enclosures. The IP20 rating applies with conductors connected and the distribution board installed — it's not rated for washdown or outdoor exposure without an enclosure.