Siemens 5SU9356-1CN63 — RCBO for 63 A final circuits
The Siemens 5SU9356-1CN63 is a 2-pole residual-current-operated circuit breaker (RCBO) from the SENTRON series, combining overcurrent and earth-fault protection in a single 36 mm-wide (2 MW) DIN-rail module. It is rated 63 A at 30 °C with a C tripping characteristic and a 30 mA residual-current trip, making it the primary choice for general-purpose socket-outlet circuits and mixed resistive-inductive loads in commercial and residential distribution boards where both overload and residual-current protection are required in one device.
Rated current and thermal derating
The 63 A rating holds at 30 °C ambient. At 40 °C it derates to 58.6 A, at 45 °C to 56.1 A, at 50 °C to 54.8 A, and at 55 °C to 53.6 A — a 15 % drop from the 30 °C figure. If the panel ambient runs above 40 °C, the continuous load must be sized against the derated value, not the nameplate 63 A, to avoid nuisance tripping in sustained operation.
Mounting and integration
Mounts on standard DIN rail in any position. The 36 mm width (2 modular units) and 77 mm depth fit standard distribution board cutouts; installation depth is 70 mm.
Residual current type and design
The residual-current element is Type AC — it detects sinusoidal AC earth-fault currents only. For circuits with pulsed DC or smooth DC fault components (e.g., variable-speed drives, UPS systems, LED drivers), a Type A or Type B RCD would be required. The design is instantaneous (no intentional time delay), so it trips within the standard RCD response time on a 30 mA fault. This is suitable for general socket-outlet protection but not for selectivity with upstream delayed RCDs.