The Siemens 5SU1354-1RC25 is a SENTRON RCBO — a combined residual current circuit breaker with overcurrent protection — rated 25 A with a C tripping characteristic and 30 mA Type AC residual sensitivity. It occupies 2 modular width units (36 mm) on a DIN rail, making it a straightforward drop-in for a standard 2-pole 1P+N distribution board slot.
What the ratings mean for the panel
The C characteristic means the magnetic trip fires at 5 to 10 times rated current — so for a 25 A RCBO, instantaneous trip occurs between 125 A and 250 A. That's the standard choice for motor-starter and lighting circuits where inrush is moderate; it avoids nuisance tripping on transformer or capacitor loads that a B-curve might catch. Breaking capacity is 10 kA per EN 60898 and 20 kA per IEC 60947-2. EN 60898 is the residential / commercial standard; the higher 20 kA rating under IEC 60947-2 means this RCBO is also rated for industrial distribution where fault currents can be stiffer. That dual-rating gives you headroom — if the prospective short-circuit current at the panel is under 10 kA, the EN rating covers it; if it's between 10 and 20 kA, the IEC rating still holds. The 30 mA Type AC residual sensitivity catches sinusoidal AC earth faults — the standard for general-purpose socket-outlet and lighting circuits. It's not suitable for pulsating DC or smooth DC faults (those need Type A or Type F), so if the downstream load includes VFDs, UPS systems, or LED drivers, spec the A-type variant instead. IP20 with connected conductors is the norm for enclosed distribution boards — the RCBO itself isn't sealed against dust or moisture ingress, so it lives inside a cabinet rated for the environment.
Panel fit and wiring
Mounts on standard DIN rail — any mounting position, supply feed from top or bottom. Two modular width units (36 mm wide,) means it occupies the same footprint as a standard 2-pole MCB. Depth is 70 mm, so it clears most 80 mm deep enclosures. Rated insulation voltage (Ui) is 264 V, overvoltage category III, pollution degree 2. That's the standard specification for fixed-installation distribution boards in residential and commercial settings.