The Siemens 5SU9353-7CN50 is a 1P+N RCBO (residual current circuit breaker with overcurrent protection) from the SENTRON series, combining a 50 A C-curve MCB with a 30 mA Type A RCD in a single module. The C-characteristic means it handles moderate inrush currents typical of motor and lighting loads, tripping between 5 and 10 times rated current for short-circuit protection. The 30 mA Type A residual current detection catches sinusoidal AC faults and pulsating DC faults up to 6 mA smooth DC — the standard choice for circuits with single-phase electronics, switched-mode power supplies, or variable-speed drives downstream.
Breaking capacity and coordination
Rated at 4.5 kA (Icn) at 230 V AC, this RCBO is sized for residential and light commercial distribution boards where the prospective short-circuit current at the point of installation stays under that threshold. In a panel with a higher upstream fault level — say a 10 kA or 16 kA main breaker — you need to verify the back-up protection or current-limiting device to ensure the RCBO is not subjected to a fault it cannot interrupt. The 1P+N form factor (switched phase, solid neutral) fits standard single-phase final circuits in TN or TT earthing systems.