RCD-unit for equipment and fire protection in 4-wire systems
The Siemens 5SM2645-6 is a 4-pole SENTRON residual current device (RCD) rated 63 A at AC and 300 mA fault current, designed for instantaneous tripping in 50 Hz networks. Type A detection means it catches sinusoidal AC faults plus pulsating DC residual currents — the standard choice for circuits with single-phase rectifiers, switched-mode supplies, or variable-speed drives that generate half-wave DC leakage.
Depth of 77 mm and installation depth of 70 mm leave clearance for wiring ducts and gland plates in a typical 200 mm deep enclosure. Supply connection from top or bottom — no mandatory orientation, which simplifies busbar routing in a distribution board. IP20 with connected conductors and installed distribution board; degree of pollution 2, overvoltage category III, so it's suited for fixed indoor installations in commercial or industrial switchgear.
Thermal derating and continuous current capability
At 45 °C it's 58.59 A, at 50 °C it's 56.7 A, and at 70 °C it drops to 50.4 A. The full thermal curve means a panel builder sizing a 4-pole RCD for a 63 A busbar must account for the actual enclosure ambient — if the distribution board sits next to a heat source or in a non-ventilated cabinet, the effective continuous current may be lower than the 63 A label. Rated insulation voltage 460 V, surge current resistance 1 kA, surge voltage resistance 4 000 V — standard for 400/415 V three-phase networks.
Listed as current production (active lifecycle stage). No end-of-life notice or last-time-buy date on record. The 5SM2645-6 is a standard SENTRON RCD variant, widely specified in European-style distribution boards.