The Siemens 5SU9336-7CN40 is a combined residual current circuit breaker with overcurrent protection (RCBO) in a single 1P+N module. It integrates a Type A residual current device (RCD) rated at 30 mA with a C-characteristic miniature circuit breaker (MCB) rated at 40 A, all in a 230 V AC single-phase form factor. The 6 kA breaking capacity (Icn) covers the majority of domestic and light commercial final circuits where the prospective short-circuit current stays under that threshold.
What the ratings mean for fit
The Type A RCD at 30 mA means this unit detects sinusoidal AC residual currents plus pulsating DC residual currents up to 6 mA smooth DC — the standard requirement for circuits with single-phase rectified loads (washing machines, LED drivers, IT equipment). The 30 mA trip threshold provides personal protection against direct contact, not just fire prevention. The C-characteristic (C-Char) on the overcurrent side means the magnetic trip operates at 5 to 10 times In (200–400 A), suited for loads with moderate inrush like small motor circuits, lighting banks, or multiple socket outlets. The 40 A rating is sized for a 40 A final submain or a high-demand ring/radial final circuit.