What it is and what it does
The Siemens SENTRON 5SM2725-0 is a 2-pole residual current unit (type AC) designed for use with the 5SY series miniature circuit breakers. It provides earth fault protection in 50 Hz AC systems at a rated voltage of 230/400 V, with a rated residual current of 500 mA and a rated current of 63 A. The RC unit snaps onto a DIN rail (REG mounting) and occupies 2 width units (36 mm at 18 mm per unit), sitting in any mounting position. It is finger- and back-of-hand safe (IP20 with connected conductors in an installed distribution board) and carries overvoltage category III.
Thermal derating and conductor sizing
At 40 °C the 5SM2725-0 is rated at 58.59 A, and at 45 °C it holds the same 58.59 A. Derating begins above 45 °C: 56.7 A at 50 °C, 54.81 A at 55 °C, 53.55 A at 60 °C, 52.29 A at 65 °C, and 50.4 A at 70 °C. The ambient operating range is -5 to +45 °C; storage range is -40 to +75 °C. Terminals accept solid or stranded conductors from 1.5 mm² up to 25 mm², with a tightening torque of 2.5 to 3 N·m. Supply connection can be made from the top or bottom. Installation depth is 70 mm.