The Siemens SENTRON 5SM3344-4KK14 is a 4-pole residual current circuit breaker (RCCB) rated for 40 A at 40 °C, with a 30 mA Type B+ residual current sensitivity and a short-time delayed design.
The Type B+ residual current detection covers AC, pulsating DC, smooth DC, and high-frequency AC residual currents — critical for variable-speed drives, UPS systems, and EV charging infrastructure where standard Type A RCCBs would be blind to DC fault components. The short-time delayed design (short-time delayed) means it withstands transient surge currents up to 3 kA without nuisance tripping, making it suitable for circuits with capacitive inrush or surge arrestors downstream. Rated current derates with ambient temperature: 40 A up to 45 °C, then 37.6 A at 50 °C, stepping down to 28 A at 70 °C. The 72 mm width and 90 mm height fit standard distribution board cutouts. Silicon-free construction matters for automotive and paint-shop applications where silicone outgassing can cause adhesion or surface defects.