What this reversing assembly delivers
The 3RA2318-8XB30-1FB4: This is a Siemens SIRIUS reversing contactor assembly — two 3RT2018-1FB42 contactors mechanically interlocked in a single housing, so you get forward-reverse control without wiring your own interlock and risking a phase-to-phase short during a midnight startup. Coil is 24 V DC with a built-in diode surge suppressor — no external flyback diode needed on the PLC output. The coil terminals are screw-type, same as the main circuit, so one tool handles the whole assembly.
Mounting and panel fit
Size S00 frame, 90 mm wide by 68 mm tall by 73 mm deep — it screws or snaps onto 35 mm DIN rail. Clearance around the assembly: 6 mm upwards, forwards, downwards, and to the side — zero mm backwards. That tight rear clearance means it sits close to the backplane, so plan the wiring duct depth accordingly.
Wiring terminals and conductor sizes
That covers most motor feeds up to 4 mm² without needing ferrules on stranded wire. The supplied RH assembly kit (3RA2913-2AA1) is included — that's the mechanical interlock bracket and shaft that ties the two contactors together so only one can close at a time.
Operating conditions and life
The mechanical life of the contactor is 10 million operations typical — that's the relay, not the assembly, but it's the wear item you'll replace first. Vibration resistance: 11.4 g for 5 ms and 7.3 g for 10 ms on both AC and DC — that's the shock rating, not continuous vibration. For continuous vibration environments, check the mounting rail damping.
Sourcing and compliance
RoHS compliance date is 10/01/2009 — it meets the original RoHS directive.