The Siemens 5SU9106-1KK45 is a SENTRON RCD-operated circuit breaker — an RCBO that combines overcurrent protection and residual-current detection in a single 18 mm-wide, 1-pole-plus-neutral package. It's rated 45 A at 30 °C, breaking capacity 6 kA per EN 60898 and IEC 60947-2, with a Type C tripping characteristic and AC fault-current sensing.
The 45 A rating at 30 °C is the headline number, but out here in the grease you need to check the derating curve: at 40 °C it's 42.3 A, at 45 °C it's 40.95 A, at 50 °C it's 39.15 A, and at 55 °C it's 36.45 A. If your panel runs hot — near a drive or transformer — size the load accordingly or step up a frame. It's an instantaneous (non-delayed) RCD for AC fault currents only — no time delay, no DC or pulsating DC sensitivity. Mount it on a DIN rail in any position; the supply can come from top or bottom. Installation depth is 70 mm, overall depth 77 mm, width 18 mm (1 width unit), height 125 mm.