What it is and what it does
The Siemens 5SU9356-7KN50 is a 1P+N RCD-operated circuit breaker (RCBO) from the SENTRON 5SU9 series, combining overcurrent protection and residual current detection in a single 36 mm wide (2 MW) module. It is rated 50 A with a C tripping characteristic and Type A fault current sensitivity, meaning it detects both sinusoidal AC and pulsating DC residual currents — the standard requirement for circuits with single-phase rectifiers, switched-mode power supplies, or variable-speed drives. The unit carries a 6 kA breaking capacity per EN 60898 and 10 kA per IEC 60947-2, covering most residential and light commercial panelboard applications.
Ratings and what they mean for the panel
The 50 A rating is the continuous current at 30 °C ambient; at 40 °C it derates to 47 A, at 45 °C to 45.5 A, at 50 °C to 43.5 A, and at 55 °C to 40.5 A. If the panel ambient runs above 30 °C, use the derated figure for the load calculation — the 50 A nameplate applies only at the reference temperature. The Type A fault current detection (30 mA typical for this class) handles residual currents from electronic loads that a simple AC type would miss. Combined with the C characteristic (magnetic trip at 5–10× In), it is suited for circuits with motor inrush or capacitive loads that would nuisance-trip a B curve. Terminals accept solid or stranded conductors from 0.75 to 35 mm², covering most branch-circuit wire sizes up to 4 AWG. The supply can enter from either top or bottom, and the unit can be mounted in any orientation — useful when panel layout forces a rotated position. Power dissipation is 1.5 W maximum, which matters for thermal budgeting in a densely populated enclosure. The unit is halogen-free and silicon-free, a requirement in some clean-room or corrosive-environment specifications.
Mounting and integration
Snap-on mounting to DIN rail EN 60715, 36 mm width (2 MW), 90 mm height, 77 mm depth (70 mm installation depth). IP20 rated when installed in a distribution board with connected conductors. Overvoltage category III, pollution degree 2 typical for fixed-installation switchgear. The unit is touch-protected per the product feature.