RCD-operated circuit breaker, 10 A, 10 mA — what the ratings mean
The Siemens SENTRON 5SU9156-7VK10 is a 2-pole RCBO combining overcurrent protection (Class C trip characteristic, 10 A rated) with residual current detection (10 mA, Type A) in a single 36 mm wide module — two modular width units on the DIN rail. The 10 mA trip threshold catches leakage paths that a standard 30 mA RCD would miss, which makes it the right choice for circuits supplying wet-area equipment or medical IT rooms where lower leakage tolerance is specified. Type A detection covers pulsating DC residual currents from half-wave rectified loads (typical in switching power supplies and variable-speed drives), so it handles the modern load mix better than a Type AC device. Rated breaking capacity is 6 kA per EN 60898, which is standard for domestic and light commercial final circuits in most European installations. The insulation voltage is rated 264 V (Ui), and the surge voltage resistance is 4 000 V, consistent with overvoltage category III — meaning it's designed for fixed installations downstream of the main distribution board, not for direct utility connection.
Thermal derating — the real current you get at panel temperature
The 10 A rating at 30 °C drops to 9.4 A at 40 °C, 9.1 A at 45 °C, 8.7 A at 50 °C, and 8.1 A at 55 °C. That derating curve matters when the RCBO sits in a crowded enclosure with other heat sources — a panel running at 50 °C ambient means the device is effectively an 8.7 A breaker, not 10 A. The mounting position is any orientation, so vertical or horizontal DIN rail doesn't change the thermal performance.
Panel integration — footprint and clearance
Width is 36 mm (2 MW), depth 77 mm, height 90 mm, with an installation depth of 70 mm. The IP20 rating applies only when the distribution board is installed and conductors are connected — so during panel assembly before the cover is on, treat it as a touch-protected device, not sealed. Power supply cord can enter from either top or bottom, and the touch-protection feature is built in (no separate finger duct needed). Halogen-free and silicon-free construction keeps it compliant for clean-room or sensitive-environment panels where outgassing matters.