The Siemens SENTRON 5SM3321-4KK14 is a 2-pole residual current circuit breaker (RCCB) rated at 16 A with a 30 mA trip threshold, designed for 50 Hz systems. Its Type B+ residual current characteristic means it detects AC, pulsating DC, smooth DC, and high-frequency AC residual currents — covering variable-speed drive leakage and inverter-fed loads that a standard Type A would miss. The short-time delayed design (selective / S-type) provides coordination with downstream RCCBs, so a fault on a branch trips the branch device before this main unit, keeping the rest of the panel live.
Mounts on DIN rail (REG) in any position, occupying 4 modular width units. Depth is 70 mm, width 72 mm, height 90 mm. IP20 protection applies when installed in a distribution board with connected conductors — standard for enclosed panel use. Silicon-free construction suits environments where silicone outgassing can contaminate contacts or optics.
Rated short-circuit current (SCCR) is 10 kA per IEC 61008-1, with a lower 0.8 kA rating per EN 60898. The I²t let-through is 70 000 A²·s; surge current resistance is 3 kA. Overvoltage category III. Rated supply voltage frequency 50 Hz. The test circuit minimum voltage is 195 V. Supply connection can be top or bottom; for SIGRES function, bottom connection keeps the test circuit active even when the RCCB is switched off.
Rated current derates with ambient temperature: 16 A at 40 °C, 16 A at 45 °C, 15.04 A at 50 °C, 14.08 A at 55 °C, 13.12 A at 60 °C, 12.16 A at 65 °C, 11.2 A at 70 °C. Operating ambient range is -25 °C to 45 °C; storage range -40 °C to 75 °C.