Selective RCCB for feeder discrimination
The Siemens 5SV3642-8 is a 4-pole selective residual current circuit breaker (RCCB) from the SENTRON family, rated 25 A with a 300 mA residual operating current at 400 V AC. The selective design (time-delayed) means it coordinates with downstream instantaneous RCDs — in a fault, the downstream device trips first, keeping this unit closed so only the faulted branch drops, not the whole sub-distribution board. That makes it the right choice for a feeder or main switch position where you need discrimination from branch RCDs. Type A detection covers AC sinusoidal and pulsating DC residual currents — the common profile for single-phase rectified loads like switching power supplies, LED drivers, and variable-speed drives. For a 4-pole device on a 400 V three-phase supply, that covers the full mixed-load panel.
Depth is 70 mm, which matches the 70 mm installation depth — no extra projection beyond the rail. The 60 mm grid spacing aligns with standard distribution board cutouts. Mounting position is unrestricted, so it can go in any orientation within the enclosure.
Short-circuit and thermal performance
Rated short-circuit current withstand is 10 kA per IEC 61008-1, with a permissible series fuse short-circuit current of 100 A maximum. Power dissipation per pole is 0.8 W in hot operating state — negligible for enclosure thermal budgeting. The -25 °C lower limit covers most unheated utility rooms; if the panel sits in a freezer or exterior enclosure in a cold climate, verify the ambient stays above that.