What this RCBO carries and where it fits
The Siemens 5SU1353-1KL20 is a 1P+N RCBO from the SENTRON 5SU1 series, combining overcurrent and residual current protection in a single 36 mm wide module (2 width units). It is rated 20 A with a C tripping characteristic and a 4.5 kA breaking capacity per EN 60898, meaning it handles moderate inrush from motor or lighting loads while providing fault current interruption up to 4.5 kA. The AC fault current type covers sinusoidal residual currents — the common case for most commercial and light industrial circuits. Rated current derates with ambient temperature: 20 A at 30 °C, dropping to 14.6 A at 70 °C (–), so if the panel runs hot, factor that into the load schedule.
Integration into the panel
Mounts on DIN rail in any position. Installation depth is 70 mm, overall depth 77 mm. Solid and stranded conductors from 0.75 to 35 mm² are accepted — that covers most final subcircuit wiring up to 6 mm² for the load side and larger incoming tails. Power supply can enter from top or bottom, which simplifies busbar routing in a crowded enclosure. IP20 applies only when the distribution board is installed and conductors are connected; the RCBO itself is not rated for exposed or washdown locations. Halogen-free and silicon-free construction matters for environments with strict outgassing requirements, such as hospitals or clean manufacturing.
What the ratings mean for selectivity and coordination
The C-curve means magnetic trip occurs at 5 to 10 times rated current (100–200 A for this 20 A unit), which is typical for circuits with motor or transformer inrush. The 4.5 kA breaking capacity per EN 60898 is the standard domestic/commercial level — adequate for most final subcircuits downstream of a higher-rated upstream MCCB or fuse. Energy limiting class 3 indicates it lets through relatively low let-through energy during a fault, which helps with downstream coordination. Overvoltage category III confirms it is rated for fixed installation downstream of the main distribution board.