The Siemens 5SM1342-6FD is a Type A FI-Protector (PSE/SSF) — a 4-pole residual current device rated 25A with a 30mA trip threshold, designed for 400V systems. The 55mm width and 4TE (4 module units) DIN-rail footprint fit standard distribution board layouts. Type A detection handles pulsating DC fault currents from single-phase rectifiers, VFDs, or switched-mode supplies — common on mixed-load panels where pure sine-wave RCDs would nuisance-trip.
The 30mA IΔn (residual operating current) is the standard threshold for personnel protection per IEC 60364 — it clears earth faults before ventricular fibrillation risk. The 25A rated current matches the upstream MCB or fuse rating for a 4-pole circuit feeding mixed resistive and electronic loads. Type A classification means it's suitable for circuits with single-phase rectification downstream (computers, LED drivers, small VFDs); Type AC devices would not detect the pulsating DC component and could fail to trip.
Panel integration
Snap-on DIN rail mounting, 4TE wide (roughly 70mm). The 55mm depth fits standard 63A-rated enclosures without crowding the gland plate. Terminal capacity accepts up to 25mm² conductors for the main circuit; busbar-compatible for multi-pole distribution blocks.