RCBO 20 A, C-curve, 30 mA — panel-builder commissioning notes
The Siemens 5SU1354-1RC20 is a SENTRON RCBO combining overcurrent protection (20 A, C characteristic) with residual current protection (30 mA, Type AC) in a single 2-module-wide unit. It snaps onto DIN rail in any mounting position, with supply accepted from either top or bottom terminals. The 10 kA breaking capacity per EN 60898 covers residential and commercial final circuits; the 20 kA rating per IEC 60947-2 gives headroom for industrial panel applications where higher fault currents are expected. Overvoltage category III and pollution degree 2 suit fixed-installation distribution boards.
What the ratings mean for fit
The C characteristic means the magnetic trip operates at 5 to 10 times rated current — standard for general-purpose loads like lighting, socket outlets, and small appliances where inrush is moderate. The 30 mA Type AC residual sensitivity catches sinusoidal AC earth faults; it is the baseline choice for most residential and commercial circuits, not for pulsed DC or smooth DC fault types. The 20 A rating on a 2-pole 1P+N design switches the live conductor and switches the neutral, so it fits single-phase circuits where neutral isolation is required. The 2-module width (36 mm) matches standard DIN-rail cutouts; depth of 70 mm and height of 90 mm are typical for SENTRON RCBOs and clear most enclosure gland plates.
Integration — DIN-rail fit and panel considerations
Mounts on 35 mm DIN rail per EN 60715. The 2-module width (36 mm) occupies the same slot count as a standard 2-pole MCB. Supply can enter from top or bottom, which simplifies busbar routing in crowded enclosures. IP20 protection applies once the distribution board is installed with conductors connected — the RCBO itself is not sealed against washdown. Operating temperature range of -40 to 75 °C covers most indoor panel environments; derating above 40 °C follows the standard thermal curve for SENTRON devices. Humidity tolerance up to 95% non-condensing.