The 3RA2120-4BH26-0BB4 is a Siemens SIRIUS direct-on-line starter in size S0, combining a contactor and overload relay into a single assembly for snapping onto 60 mm busbar systems.
Mounting and termination — busbar snap-on with spring terminals
Designed specifically for 60 mm busbar systems, the starter snaps onto the busbar without tools — no DIN rail required, though the vertical mounting position is mandatory. Main circuit connections use spring-loaded terminals (cage clamp style), which reduces wiring time compared to screw terminals and holds solid or ferruled stranded wire without retorquing. Dimensions are 45 mm wide × 260 mm high × 165 mm deep; clearance requirements are 50 mm upward, 20 mm forward, 10 mm downward, and 20 mm at the side — plan the busbar layout accordingly.
What comes in the box — supplied contactor and link module
The starter ships with the contactor 3RT2026-2BB40 and the link module 3RA2921-2AA00 pre-assembled — no separate ordering of the contactor and overload for this combination. The supplied contactor is matched to the S0 frame size and the 20 A AC-3 rating, so the coordination between the contactor and overload is factory-set for Type 1 or Type 2 coordination depending on the upstream breaker selection.
Environmental and compliance — operating range and RoHS
Rated for operation from -20 °C to +60 °C with temperature compensation active across the same range; storage and transport limits extend from -50 °C to +80 °C. RoHS compliance date is 10/01/2009 — the starter meets the EU RoHS directive for substances of concern as of that date.