Siemens 5SV4742-0 SENTRON RCCB — 4-pole, 25 A, 500 mA trip
The Siemens 5SV4742-0 is a 4-pole residual current circuit breaker (RCCB) from the SENTRON family, rated 25 A at AC with a 500 mA residual trip current. It's an instantaneous (non-delayed) type AC device — meaning it responds to sinusoidal AC fault currents only, not pulsed DC or smooth DC residuals. The 10 kA short-circuit current rating (SCCR) per IEC 61008-1 and EN 60898 tells you it can safely interrupt a fault up to that level without welding contacts or cascading damage upstream. The I²t let-through is rated at 58 000 A²·s, and the peak let-through current is 5 200 kA — both figures the downstream equipment's withstand capability must exceed for selective coordination. Mounting is snap-on DIN rail (REG) per DIN 43880 size 1, occupying 4 modular width units (72 mm wide). The depth is 70 mm, same as the installation depth — no extra clearance needed behind the rail. Mounting position is any orientation, and supply can enter from top or bottom. The IP20 rating applies when installed in a distribution board with conductors connected; this is a panel-interior device, not for wet or outdoor locations without an enclosure. Rated current holds flat at 25 A from 40 °C through 70 °C ambient — no derating over that range. Operating ambient is -25 °C to 45 °C; storage range is -40 °C to 75 °C. Overvoltage category III, silicon-free construction. Operating frequency is 50 Hz only.
Panel integration and wiring
Four modular width units at 72 mm wide; the 70 mm depth means it sits flush with most DIN-rail mounted MCBs in the same enclosure. Spring-cage or screw terminals accept standard copper conductors — verify terminal type on the nameplate before terminating. Supply top or bottom, no polarity concern on an RCCB. The test button requires a minimum 100 V to operate the test circuit. No short-time delay means it trips instantaneously on residual current exceeding 500 mA — use a selective (S-type) RCCB upstream if you need coordination with downstream devices.