Reversing starter, S0 frame, 25 A AC-3 — what the ratings mean
The 3RA2220-4DF27-0BB4: That 25 A figure at 400 V is the motor current it handles during start and run, not the thermal overload setting; the Class 10 trip characteristic means it opens within 10 seconds at 600% of set current, matching typical compressor and conveyor starts. The control coil pulls 24 VDC nominal, so it drops straight into a 24 V industrial control bus without an interposing relay. The supplied contactor is 3RT2027-2BB40, and the link module is 3RA2921-2AA00 — the reversing interlock is built into that module, not the contactor itself.
DIN rail mounting and panel space — the S0 footprint
Mounts on a 35 mm DIN rail via an adapter for screw or snap-on fastening, mounting position vertical. The S0 frame dimensions are 130 mm deep, 90 mm wide, 269 mm tall. Clearance requirements: 50 mm upward, 32 mm forward, 0 mm backward, 10 mm downward, 10 mm at the side. The zero backward clearance means it can sit flush against a back panel — useful when the gland plate is tight. Spring-loaded terminals on the main current circuit — no screwdriver needed for the power wiring, which speeds panel build and reduces torque inspection. The terminals accept the wire gauge typical for 25 A motor circuits.
Sourcing and lifecycle — current production, quoted to order
This is not a legacy or sunset line; the SIRIUS S0 platform is the standard reversing starter for Siemens and is widely specified across European and North American panel builds. Sourced through independent distribution against an RFQ.