What the 5SM2647-6 is and what it does
The Siemens SENTRON 5SM2647-6 is a 4-pole instantaneous residual current device (RCD) rated for 100 A at 50 Hz. It is designed for Type A residual currents — meaning it detects sinusoidal AC fault currents plus pulsating DC fault currents, which covers most modern electronic loads like switched-mode power supplies and variable-speed drives. The tripping threshold is fixed at 300 mA, so it is sized for equipment protection or fire protection rather than personal shock protection (which typically uses 30 mA). The RCD is non-sealable and non-adjustable — the trip current and delay are factory-set.
Thermal derating and panel integration
The 100 A rating holds only up to 40 °C ambient. Above that, the device must be derated: 93 A at 45 °C, 90 A at 50 °C, 87 A at 55 °C, 85 A at 60 °C, 83 A at 65 °C, and 80 A at 70 °C. The operating ambient range is -25 °C to 45 °C, with storage from -40 °C to 75 °C. The RCD occupies 5 modular width units (MWU) on a DIN rail, with a width of 124 mm, depth of 70 mm, and height of 90 mm. It can be mounted in any position. The IP20 rating applies only when installed in a distribution board with connected conductors — it is not a standalone outdoor device.
Electrical ratings and coordination
The insulation voltage (Ui) is rated at 460 V, with overvoltage category III and pollution degree 2 — standard for fixed-installation distribution panels. The RCD withstands a surge current of 1 kA and a surge voltage of 4 kV. The rated fault current is 300 mA, non-adjustable. The device is instantaneous (no time delay), so it trips within milliseconds of a fault exceeding the threshold. It includes a protection function against false tripping, which helps avoid nuisance trips from transient surges.