Siemens 5SM2745-8 SENTRON Selective RCD — 63 A, 4-Pole, Type A
The Siemens 5SM2745-8 is a SENTRON-brand selective residual current device (RCD unit) designed for 4-pole applications. The selective design (time-delayed) ensures coordination with downstream RCDs, so only the faulted circuit trips — critical for maintaining supply continuity in distribution boards where nuisance tripping of an upstream device would take out multiple loads.
The 63 A AC rating at 50/60 Hz defines the continuous load this RCD can carry. Per the specification, it derates with ambient temperature: 58.6 A at 40 °C, 56.7 A at 50 °C, and 50.4 A at 70 °C. The 500 mA rated fault current is not adjustable, and the OFF-delay time is fixed (not adjustable), consistent with a selective (time-delayed) device that coordinates with 30 mA or 100 mA downstream RCDs. Type A residual current detection covers sinusoidal AC and pulsed DC up to 6 mA, which covers most modern electronic loads (switched-mode power supplies, variable-speed drives, LED drivers) that generate pulsed DC fault currents. The surge current resistance of 5 kA and surge voltage resistance of 4,000 V indicate the device withstands transient overvoltages common in industrial mains without nuisance tripping or damage. The insulation voltage (Ui) is rated at 460 V, and overvoltage category III applies — standard for fixed-installation distribution boards. Degree of pollution 2 (non-conductive pollution that becomes conductive only through condensation) is typical for enclosed panel environments.