20 A AC-3 reversing starter — SIRIUS S0 frame
The 3RA2220-4BF26-0BB4: The Class 10 trip curve means it will hold through a motor start (up to 10 seconds at locked-rotor current) but trip before the winding overheats on a sustained overload. It ships as a factory-assembled unit: the supplied contactor is a 3RT2026-2BB40, and the link module is a 3RA2921-2AA00. That means the reversing interlock and mechanical linkage are pre-configured — no field assembly of the reversing pair, no risk of wiring the mechanical interlock backwards.
Mounting and termination — DIN rail, spring terminals
Mounts on a 35 mm DIN rail via the included adapter for screw or snap-on fixing; the mounting position is vertical only. The S0 footprint is 90 mm wide, 269 mm tall, and 130 mm deep — plan for the depth when routing cables behind the panel door. Main circuit connections use spring-loaded terminals — no screw torque to verify, no loosening under vibration. The spring clamp holds the conductor without periodic re-tightening, which matters in a reversing starter where the contactor cycles frequently.
Environmental range and clearance
Rated for operation from -20 to +60 °C ambient, with storage and transport tolerance from -50 to +80 °C. The required clearances around the unit: 50 mm upward, 32 mm forward, 10 mm downward, and 10 mm at the side — no clearance needed behind the DIN rail. These matter for heat dissipation in a densely packed panel.