What This Load Feeder Delivers
The Siemens 3RA1120-4BC26-0BB4 is a SIRIUS non-fused load feeder — a pre-assembled direct starter combining a circuit-breaker, contactor, and bimetal overload relay in one size S0 housing. The 24 V DC coil matches standard PLC control voltages; the 45 mm width and 154 mm depth let it fit a 45 mm busbar center-to-center spacing on a 40 mm system.
Wiring and Mounting — Panel Fit
Snaps directly onto 40 mm busbar systems via the supplied busbar adapter 8US1051-5DM07. The 45 mm width and 183 mm height clear standard enclosure gland plates; clearance needs: 30 mm upward, 10 mm forward, 9 mm backward, 0 mm downward. Accepts solid or stranded copper from 1 to 6 mm², and can double up two conductors per terminal (2x 1–2.5 mm² or 2x 2.5–6 mm²). AWG equivalents: 2x 14–10 AWG on main contacts. IP20 front protection keeps fingers out; pollution degree 3 suits industrial control panels.
Built-In Components and Protection
Factory-integrated with a circuit-breaker 3RV1021-4BA10 for short-circuit and overload protection, a contactor 3RT1026-1BB40 for switching, and a link module 3RA1921-1BA00. Motor protection is bimetal type — thermal curve matched to the motor's heating characteristic. Rated insulation voltage 690 V, shock resistance 12.5g, ambient operating range -20 to +70 °C, storage -55 to +80 °C. No PROFINET or PROFIBUS DP onboard; this is a hardwired starter slice.