The Siemens 5SM3642-6KL is a SENTRON residual current operated circuit breaker (RCCB), 4-pole, type A, rated 25 A with a 300 mA tripping residual current at 400 V AC. It's an instantaneous design (no short-time delay), meaning it trips on the fault waveform itself without intentional delay — standard for general-purpose earth leakage protection on distribution boards.
Mounts on DIN rail (REG), occupies 4 width units (72 mm wide), and can be installed in any position — top or bottom supply feed. Depth is 77 mm with an installation depth of 70 mm, so it fits standard 80 mm deep enclosures without issue. Terminal torque spec is 2.5 to 3 N·m for the screw-type terminals, accepting solid or stranded copper from 1.5 mm² up to 25 mm².
Protection class is IP20 when installed in a distribution board with conductors connected — normal for a panel-mounted device. The housing is finger and back-of-hand safe per the protection-against-electrical-shock rating. Short-circuit current rating is 10 kA, and it's rated for overvoltage category III. Surge current resistance is 1 kA. The design is silicon-free.