Selective 4-pole RCBO for main feeder protection
The Siemens 5SU1844-6WK82 is a SENTRON selective RCBO rated 125 A at 30 °C, with a 10 kA breaking capacity per EN 60898 and IEC 60947-2. The 4-pole, Type A residual-current unit trips at 1000 mA, and the B-curve overcurrent characteristic handles moderate inrush from resistive and light motor loads. The selective design (time-delayed) means it coordinates with downstream 30 mA or 300 mA RCDs, so only the faulted branch drops out — the main feeder stays live. Panel builders mount this in the distribution board; the 11 modular-width (198 mm) footprint fits standard DIN-rail enclosures.
Rated current derating across temperature
The 125 A rating holds at 30 °C ambient. At 40 °C the continuous current drops to 115.62 A, at 50 °C to 106.25 A, and at 60 °C to 96.25 A. For a panel that runs warm — say a 50 °C internal ambient — size the upstream cable and busbar for 106 A, not the nameplate 125. The unit is halogen-free and silicon-free, which matters for clean-room or high-reliability installations where outgassing contaminates contacts or optics.
Physical fit and environmental limits
Dimensions: 198 mm wide (11 modular units), 90 mm tall, 77 mm deep, with a 70 mm installation depth into the enclosure. The supply can enter from either top or bottom, and the mounting position is unrestricted. Rated for overvoltage category III (distribution-level transients), pollution degree 2, and an ambient range of -40 °C to 75 °C. IP20 applies once the distribution board is installed with conductors connected — so it is not a washdown device; keep it inside a sealed cabinet in wet environments.