What it is and what it does
The Siemens 5SU9356-1KN32 is a SENTRON RCD-operated circuit breaker — an RCBO that combines overcurrent protection and residual current detection in a single 36 mm wide, 2-pole (1P+N) package. Rated 32 A at AC with a C tripping characteristic, it handles moderate inrush from motor starters or lighting banks without nuisance tripping, while the integrated RCD catches AC fault currents to ground. The 6 kA breaking capacity per EN 60898 covers most commercial and light industrial panel applications; if the available fault current at the board is higher, the 10 kA rating per IEC 60947-2 gives some headroom for coordination studies.
Thermal derating and real-world current
The 32 A rating holds at 30 °C ambient. At 40 °C it derates to 30.4 A, at 45 °C to 29.76 A, at 50 °C to 28.8 A, and at 55 °C to 27.84 A. If the panel runs warm — say, a crowded enclosure with multiple breakers — the 45 °C figure is the one to size against; a 32 A load on a 29.76 A breaker will trip on thermal overload, not a fault.
Mounting and wiring
Occupies 2 width units (36 mm) on a DIN rail. Installation depth is 70 mm; overall depth including terminals is 77 mm. Accepts solid or stranded conductors from 0.75 mm² up to 35 mm² — covers everything from a 1.5 mm² lighting circuit to a 10 mm² feeder. Supply can enter from either top or bottom, which simplifies busbar routing in a crowded panel. Touch protection is built in, and the IP20 rating assumes the distribution board is installed with conductors connected.