The Siemens 5SU9326-7CR25 is a 1P+N RCBO combining overcurrent and residual current protection in a single DIN-rail module. It carries a 25 A thermal-magnetic C-curve for short-circuit and overload protection, paired with a 30 mA Type A residual current element for sinusoidal AC and pulsating DC fault currents. The 6 kA rated short-circuit capacity (Icn) at 230 V AC is sized for final subcircuits in residential and light commercial distribution boards where the upstream device provides the fault current limitation.
What the ratings mean for fit
The 30 mA Type A residual element is the key differentiator here. Type A detects both sinusoidal AC faults and pulsating DC faults — the kind generated by single-phase rectifiers in washing machines, LED drivers, and switched-mode power supplies. If your circuit feeds modern electronics, a Type A RCBO catches faults an AC-only RCD would miss. The C-curve (25 A) means the magnetic trip operates at 5 to 10 times In, so it tolerates motor inrush and capacitive loads without nuisance tripping, but still clears a hard short fast enough to coordinate with a 63 A or 100 A upstream MCB.
Deployment context
Snap-on mounting to a standard 35 mm DIN rail, occupying a single 18 mm module width. The 1P+N topology switches the line conductor only; the neutral is switched internally for isolation but not protected against overcurrent. Rated for 230 V AC phase-to-neutral systems — typical for single-phase final circuits in TN or TT earthing schemes. The 6 kA Icn is adequate for most domestic and small commercial boards where the prospective short-circuit current at the outgoing terminal is limited by the service fuse or main switch.