The Siemens SENTRON 5SM3645-8 is a 4-pole selective residual current circuit breaker (RCCB), type A, rated at 125 A and 300 mA residual sensitivity on a 400 V AC, 50 Hz network. The 'selective' design means it incorporates a short-time delay so that downstream RCCBs trip first during a ground fault — this unit stays in, keeping upstream circuits live and narrowing the outage to the faulted branch. It's sized for main or submain protection in a distribution board where coordination with downstream 30 mA or 100 mA devices is required.
Rated at 125 A continuous and 400 V AC phase-to-phase, this RCCB handles the full load current of a large submain or a main switch in a commercial panel. The 300 mA residual sensitivity is intentionally higher than the 30 mA used for personal shock protection — it's meant for equipment protection and fire prevention on circuits with natural leakage, not for direct human contact. The short-circuit withstand is 10 kA per IEC 61008-1 and 1.25 kA per EN 60898; the 10 kA figure governs its installation behind a suitable upstream overcurrent device (MCB or fuse) rated to clear faults above that level.
The 70 mm installation depth is the space needed behind the panel door — check gland plate clearance if the enclosure is tight.
Listed as current-production. The SENTRON series is Siemens' standard distribution protection line, widely specified across European and Middle Eastern panels.
Installation notes
Silicon-free construction suits environments where silicone outgassing can contaminate contacts or optical surfaces — relevant for automotive paint lines or clean-room adjacent panels. The design accepts supplementary devices for alarm signaling or remote tripping.