The Siemens SENTRON 5SM3314-0LA is a 2-pole residual current operated circuit breaker (RCCB) rated 40 A at 230 V AC, with a 30 mA trip threshold and type AC sensitivity for sinusoidal AC fault currents. It includes built-in thermal overload protection, making it a combined RCCB/overload device in a single 2-module-width DIN-rail housing.
The 40 A rated current and 30 mA trip sensitivity are the two numbers that decide whether this RCCB fits your sub-distribution board. 40 A is a common main or feeder rating for a lighting or general-purpose final circuit in a residential or light commercial panel. The 30 mA trip provides personal protection against direct contact — it's the standard threshold for socket-outlet circuits and general-purpose protection in most IEC-based installations. That covers the majority of resistive and inductive loads (heaters, motors, lighting), but not pulsed DC or smooth DC fault currents from electronics, variable-speed drives, or EV chargers. For those loads you would need a type A or type B RCCB. The 2-pole construction switches both line and neutral, which is standard for single-phase 230 V AC circuits. The 2-module-width (36 mm) footprint on DIN rail fits standard distribution board spacing — it takes up two adjacent 18 mm positions.
Installation notes
Mounts on DIN rail (REG) in any position. The installation depth is 70 mm, which fits standard distribution board enclosures. Terminals accept solid or stranded conductors from 1 to 16 mm², with a tightening torque of 2.5 to 3 N·m for screw-type terminals.