The Siemens 5SM3342-6KL is a SENTRON 5SM3-series residual current circuit breaker (RCCB), 4-pole, Type A, rated 25 A at 400 V AC with a 30 mA trip threshold. It's an instantaneous (short-time-delay-free) device, meaning it trips on the residual current waveform without intentional delay — the go-to for general-purpose shock protection in TN and TT systems. Type A detection covers AC residual currents plus pulsating DC — the common waveform from single-phase rectifiers, variable-speed drives, and switching power supplies. If your downstream loads include electronics or motor drives, Type A is the correct choice over the simpler AC-only type. The 1 kA surge current resistance (I_{m}) covers the inrush from capacitive loads or nearby lightning-induced surges without nuisance tripping.
Mounts on DIN rail (REG profile) in any orientation — no top/bottom restriction on the supply side. Occupies 4 width units (72 mm wide) at a depth of 77 mm and height of 90 mm, with an installation depth of 70 mm behind the panel door. The N-left design means the neutral pole is on the left side of the device when viewed from the front; verify this matches your distribution board's busbar arrangement before wiring. Tightening torque is 2.5 to 3 N·m — use a torque screwdriver; under-torquing creates a high-resistance joint that can thermally damage the device over time. IP20 protection applies only when installed in a distribution board with conductors connected; the device itself is not sealed against dust ingress.