What this reversing starter is and what it delivers
The Siemens 3RA2220-4DB27-0AK6 is a SIRIUS reversing starter in size S0, combining a contactor pair, a thermal overload relay, and a circuit breaker into one assembly for reversing motor control. The thermal overload release is bimetallic (Class 10 trip class), protecting the motor against sustained overloads. The magnetic short-circuit trip handles fault clearing independently of the overload, so a bolted fault opens the circuit breaker section without waiting for the bimetal to heat.
Mounting and integration into a panel
Envelope dimensions are 265 mm high by 90 mm wide by 120 mm deep, with the mounting position specified as vertical. Main power circuit connections use screw-type terminals, which is the standard for panel builders who prefer a positive clamped connection over spring cages for higher-current reversing circuits.
What is supplied in the assembly
The reversing starter ships as a pre-assembled unit containing the supplied contactor 3RT2027-1AK60, the supplied circuit breaker 3RV2021-4DA10, the supplied link module 3RA2921-1AA00, and the supplied RH assembly kit 3RA2923-1BB1. This is a type of assignment 2 coordination — the circuit breaker and contactor are matched so that under a short circuit the starter remains usable after the fault (no contactor welding), per IEC 60947-4-1.