The Siemens SENTRON 5SM3342-4 is a 4-pole residual current circuit breaker (RCCB) rated at 25 A with a 30 mA trip threshold, Type B detection, and short-time delayed switching — built for universal current-sensitive protection on 400 V AC, 50/60 Hz networks.
Type B residual current detection covers AC, pulsating DC, smooth DC, and high-frequency AC fault currents — the only type that catches rectifier-fed loads, VFD leakage, and UPS ground faults without nuisance tripping. Short-time delayed design means it withstands brief inrush or surge currents up to 3 kA without tripping, making it suitable for circuits with capacitive loads or equipment that draws a startup pulse. Above that, the curve steps down: 23.5 A at 50 °C, 22 A at 55 °C, 20.5 A at 60 °C, 19 A at 65 °C, 17.5 A at 70 °C (–). If the panel runs hot, size the upstream breaker accordingly. The let-through current is capped at 7 500 A and the I²t at 70 000 A²·s.
Snap-on DIN rail (REG) mounting in any orientation. Occupies 4 modular width units — 72 mm wide, 90 mm tall, 77 mm deep plus 70 mm installation depth. Silicon-free construction — relevant for automotive or paint-shop panels where silicone outgassing can cause adhesion or coating defects.