The Siemens 5SM1614-0FD is a Type AC residual current device (RCD) from the FI-Protector family, rated 40A, 2-pole, with a residual operating current (IΔn) of 0.3A at 230V. The Type AC designation means it detects sinusoidal AC residual currents only — the standard choice for general-purpose circuits without non-sinusoidal or pulsating DC fault profiles. The 0.3A trip threshold is higher than the common 30mA (0.03A) for personnel protection; this unit is sized for equipment or fire protection where a higher leakage tolerance is acceptable, or where nuisance tripping from downstream electronics would be an issue.
The 55mm width and 2TE (two module spaces) form factor snap onto standard DIN rail. The 0.3A IΔn means this RCD coordinates with downstream MCBs rated up to 40A without nuisance tripping from normal cable capacitance or equipment leakage.