What it is and what it does
The Siemens 5SM3622-4 is a 2-pole Residual Current Circuit Breaker (RCCB) from the SENTRON 5SM3 series, designed for 230 V AC single-phase circuits. It is rated at 25 A with a 300 mA residual tripping current, Type B, meaning it detects AC, pulsating DC, and smooth DC fault currents — essential for circuits with variable-speed drives, UPS systems, or PV inverters that can generate DC leakage. The short-time delayed characteristic (marked as short-time delayed / K-type in some references) provides selectivity against nuisance tripping from transient surges or inrush currents, making it suitable for sub-distribution boards where coordination with downstream RCCBs is needed. The 10 kA short-circuit current rating (SCCR) means this device can safely interrupt fault currents up to 10 kA at 230 V AC without welding its contacts or failing catastrophically — a standard requirement for commercial and industrial panelboards where the prospective fault current is known to be below that threshold. Overvoltage category III confirms it is rated for fixed installation downstream of the main distribution board.
Where it goes and how it fits
Mounts on a standard DIN rail (EN 60715) and occupies 4 width units (72 mm) of panel space. The 70 mm installation depth matches the common 70 mm depth of distribution boards and enclosures — no extra clearance needed behind the rail. Mounting position is any, so it can be installed sideways or upside-down if the enclosure layout demands it, though the supply cord position is top or bottom (bottom also maintains the SIGRES function even when switched off). IP20 protection applies only when the distribution board is installed with connected conductors — standard for enclosed panel use, not for wet or dusty environments. The housing is finger and back-of-hand safe per the protection against electrical shock rating.
What the ratings mean for your panel
The 300 mA residual rating is not for personnel protection (that requires 30 mA or less) — it is sized for equipment protection and fire prevention in circuits where a 30 mA device would nuisance-trip due to natural leakage from filters, drives, or long cable runs. The short-time delayed design (3 kA surge current resistance) lets it ride through lightning-induced surges or capacitor-switching transients without tripping, while still clearing a genuine earth fault. Silicon-free construction (product feature / silicon-free: Yes) matters for automotive paint-shop or semiconductor fab installations where silicone outgassing can cause adhesion or contamination issues. Mechanical service life of 10 000 switching cycles is typical for a protective device — not a contactor, so it is not intended for frequent operational switching.