The Siemens 5SU9156-7VK25 is a SENTRON RCBO — a combined overcurrent and residual-current device in a 2-module (36 mm wide) package. The Type A fault-current detection catches pulsating DC faults up to the rated residual current, which matters for VFD-fed loads and single-phase rectifier circuits common in industrial control panels.
The 6 kA EN rating is the domestic/commercial standard; the 10 kA IEC rating gives headroom for higher available fault current in plant-floor panels.
Thermal derating and conductor sizing
At 40 °C it derates to 23.5 A, at 45 °C to 22.75 A, at 50 °C to 21.75 A, and at 55 °C to 20.25 A. The terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm², which covers everything from 1.5 mm² lighting circuits to 10 mm² feeder tails.
Snaps onto standard DIN rail, 36 mm wide (2 width units), 90 mm tall, 77 mm deep with 70 mm installation depth. Mounting position any orientation. Supply can enter from top or bottom — no mandatory polarity for the line/load side. IP20 with the distribution board installed and conductors connected; overvoltage category III, so it's rated for fixed installation downstream of the main panelboard. Halogen-free and silicon-free construction, which matters for clean-room or semiconductor-adjacent installs where outgassing contaminates optics.
Listed as current production. The 5SU9 series is Siemens' standard RCBO line for the European and export markets; no phase-out notice or last-buy window is published for this order code.