The Siemens SIRIUS 3RA2220-1HB24-0BB4 is a reversing starter — a single assembly that combines two contactors mechanically interlocked, a link module, and a Size S00 circuit-breaker into one unit for reversing motor direction. It is rated for AC-3 switching duty at 8 A on a 400 V supply, which means it handles the inrush and breaking of a three-phase induction motor up to that current without welding the contacts. The Trip Class 10 overload curve gives the motor 10 seconds of locked-rotor time before tripping — the standard for most general-purpose conveyor, pump, and fan loads. The unit ships with the 3RT2024-1BB40 contactor and the 3RA2921-1BA00 link module pre-assembled. The 24 V DC coil (24... 24 V rated value) is held in by the control voltage; dropout is below the typical threshold for that rail.
The headline motor rating is 8 A at AC-3 at 400 V — that is the current the starter can make and break for a squirrel-cage induction motor under full load. At 460/480 V the same unit is rated 5 hp, and at 575/600 V it covers 7.5 hp. The AC-3e rating extends to 690 V maximum, so the same assembly works on 690 V line supplies common in European heavy industrial installations, though the current must be derated per the manufacturer's curve. The Size S0 load feeder frame and the Size S00 circuit-breaker are mechanically coordinated: the breaker's magnetic trip clears a short-circuit fast enough that the contactor does not weld. This is Type 2 coordination by default — after a fault you replace only the breaker, not the contactor stack.