What this RCBO is and what it carries
The Siemens 5SU1354-7RC20 is a combined residual current circuit breaker with overcurrent protection (RCBO) from the SENTRON family, rated 20 A with a C tripping characteristic and 30 mA Type A residual current sensitivity. It is a 2-pole device (1P+N) protecting one live conductor, occupying 2 modular width units (36 mm) on a DIN rail. The C-curve means it trips between 5 and 10 times rated current — suited for inductive or motor-starting loads where inrush exceeds the B-curve threshold. Type A residual current detection catches pulsating DC fault currents, which standard AC-only RCDs miss — common on single-phase rectified loads like switched-mode power supplies or variable-speed drives.
Breaking capacity and where it fits
Rated breaking capacity is 10 kA per EN 60898 and 20 kA per IEC 60947-2 — the higher IEC figure applies when the device is used as a standalone circuit breaker rather than a domestic MCB. Overvoltage category III and pollution degree 2 mean it is rated for fixed-installation distribution boards, not for outdoor or heavy-industrial environments with conductive dust. Supply voltage is AC at 50 Hz only.
Panel integration notes
Mounts on a standard DIN rail in any orientation; supply can enter from top or bottom, which simplifies busbar routing in crowded enclosures. IP20 rating applies only when installed in a distribution board with conductors connected — the device itself is not sealed against dust ingress outside the enclosure. Rated insulation voltage is 264 V, surge voltage resistance 4 kV — adequate for residential and light-commercial sub-distribution boards. Ambient temperature range of -40 °C to +75 °C covers most indoor and sheltered outdoor installations; derate the 20 A rating above 40 °C per the manufacturer's thermal curve.