Selective RCCB for feeder protection — 63 A, 300 mA, Type A
The Siemens 5SM1646-8 is a 4-pole selective RCCB from the SENTRON series, rated 63 A at 40 °C and 300 mA residual trip current, Type A. Selective design means it incorporates a short time delay so that downstream RCCBs trip first during a ground fault — only if the fault persists does this unit open, keeping upstream feeders live for the rest of the panel. That coordination is critical in a distribution board feeding multiple sub-circuits: you don't want a single branch fault blacking out the whole board. Rated 400 V AC, 50 Hz, with a short-circuit current rating of 10 kA per IEC 61008-1 and 0.8 kA per EN 60898. Mounts on DIN rail (REG), occupies 4 width units (about 72 mm), and can be installed in any position.
Rated 63 A at 40 °C and 45 °C ambient; derates to 60.48 A at 50 °C, 57.96 A at 55 °C, 55.44 A at 60 °C, 52.92 A at 65 °C, and 50.4 A at 70 °C.
Fit and integration notes
Four-pole device, 55 mm installation depth. Finger and back-of-hand safe per the protection class. Silicon-free construction. Surge current resistance rated 5 kA; I²t let-through 70 000 A²·s. Test circuit requires minimum 100 V AC to operate the test button.