What it is and what it protects
The Siemens 5SU1656-1KK10 is a 2-pole SENTRON RCBO — a combined residual-current circuit breaker and overcurrent protective device in a single 36 mm-wide (2-module) unit. It's rated 10 A with a C-curve trip characteristic and a 30 mA AC-type residual current sensor. That means it protects a circuit against both overload/short-circuit (the C-curve handles moderate inrush, typical for motor starters and lighting banks) and earth-leakage faults (the AC type detects sinusoidal AC residual currents). The 30 mA sensitivity is the standard for personal protection against indirect contact in TN and TT systems. Breaking capacity is rated at 6 kA per EN 60898 and 15 kA per IEC 60947-2. The higher IEC figure matters when the RCBO sits downstream of a transformer or in an industrial panel where prospective fault current can exceed the domestic 6 kA limit. The 15 kA rating gives it headroom for coordination with upstream devices in a selective scheme.
Thermal derating — the real current rating in a warm panel
The 10 A rating is at 30 °C ambient. In a real panel — say 40 °C to 50 °C — the continuous current must be derated: 9.5 A at 40 °C, 9 A at 50 °C, 8.5 A at 60 °C, and 8 A at 70 °C. If the RCBO is mounted in a crowded enclosure or near other heat sources, the effective trip point shifts. Plan the load at the derated value for the expected ambient, not the 30 °C nameplate figure. The device is halogen-free and silicon-free, which matters in clean-room or corrosive environments where outgassing from standard plastics can contaminate contacts or optics. Mounting position is unrestricted — install it any orientation in the distribution board. The 77 mm depth and 70 mm installation depth fit standard DIN-rail enclosures; the IP20 rating assumes the board is closed and conductors are connected.