The Siemens SENTRON 5SU1644-7KK82 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) rated 125 A at 30 °C, with a 300 mA Type A residual-current trip and a C tripping characteristic. The 11-module-wide body (198 mm) mounts in any position — useful when the gland plate is tight and you need to rotate the assembly for cable entry from top or bottom.
Derating and thermal profile
The 125 A nominal rating holds at 30 °C ambient. At 40 °C it derates to 115.62 A, at 50 °C to 106.25 A, and at 60 °C to 96.25 A.
Residual-current and overcurrent coordination
The 300 mA threshold is typical for fire protection in distribution sub-mains rather than personal shock protection (30 mA is the usual for socket-outlet circuits).