RCCB for panel builders and spares planners
The Siemens 5SM3644-0KL is a 4-pole SENTRON RCCB, type AC, rated 40 A with a 300 mA residual trip at 400 V AC, 50 Hz. It mounts on DIN rail, occupies 4 width units, and has a 70 mm installation depth. This is an instantaneous-trip RCCB. It trips when residual current exceeds 300 mA. It handles AC fault currents only.
Installation notes
Mounts in any position on DIN rail. Power supply can feed from top or bottom. Accepts conductors from 1.5 mm² to 25 mm² — the 25 mm² maximum covers most feeder and subfeed sizes in a distribution board. The device is finger and back-of-hand safe (IP20 when installed in a distribution board with connected conductors). Overvoltage category III, so it's rated for fixed installation downstream of the main distribution board. Silicon-free construction avoids outgassing issues in sensitive environments. Mechanical service life is 10 000 switching cycles typical — adequate for an RCCB that sees infrequent manual operation (test button, isolation) but not designed for frequent switching under load. The test circuit requires at least 100 V AC to function.