What this part is and what it does
The Siemens SENTRON 5SU9406-1KK10 is an RCD-operated circuit breaker — an RCBO that combines overcurrent protection and residual current detection in a single 18 mm wide module for the SENTRON 5SU9 series. Rated 10 A at 30 °C with a C tripping characteristic, it handles the moderate inrush of motor starters and control transformers common in industrial panels, provided the ambient stays within the -25 to +45 °C range. The 6 kA breaking capacity per EN 60898 and IEC 60947-2 holds the unit on the grid under a hard fault, provided the prospective short-circuit current at the installation point does not exceed that level.
Ratings and what they mean for the panel
The 10 A rating at 30 °C derates 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. If the distribution board runs warm — say, a packed enclosure with multiple RCBOs — the effective continuous current drops; size the branch circuit load against the 40 °C or 45 °C column, not the 30 °C headline. The C curve (tripping between 5× and 10× In) is chosen for loads with a magnetic inrush component, such as small contactor coils or control transformers, provided the peak inrush does not exceed 100 A. The 1P+N configuration protects the phase conductor and switches the neutral, but only the phase pole is protected against overcurrent — the neutral pole is switched only. The RCBO detects AC fault currents (Type AC), so it responds to sinusoidal residual currents; it is not rated for pulsed DC or smooth DC fault currents, which limits its use on variable-speed drive outputs or UPS-fed circuits unless an upstream Type A or B RCD covers those waveforms. Energy limiting class 3 means the device restricts let-through energy to a low level, reducing stress on downstream wiring and connected equipment during a short-circuit event. Touch protection is provided on the busbar side, which simplifies panel assembly without requiring additional insulating shrouds over the line terminals.
Mounting and integration into the enclosure
Snap-on mounting to a 35 mm DIN rail, occupying one width unit (18 mm). The installation depth is 70 mm, with an overall depth of 77 mm — the extra 7 mm accounts for the front-mounted test button and toggle. Mounting position is unrestricted, so the RCBO can be installed horizontally or inverted if the enclosure layout demands it, provided the ambient temperature limits are still met. Supply can enter from either the top or bottom terminals, which is useful when busbar feed comes from below. Terminals accept solid or stranded conductors from 0.75 to 35 mm², which covers everything from 1.5 mm² control wiring up to 10 mm² feeder tails. The IP20 rating applies only when the distribution board is installed and conductors are connected — the RCBO itself is not sealed against dust ingress during panel assembly.