Module overview and fit
The Siemens 6ES7422-1FF00-0AA0 is an SM 422 digital output module for the S7-400 programmable logic controller. It provides 8 discrete outputs rated at 5 A each for 120/230 V AC loads, with optical isolation between the backplane and field wiring. This is the module you slot into a 400-series rack when you need to switch high-voltage AC actuators — contactors, solenoid valves, motor starters — directly from the PLC, without an interposing relay bank.
What the ratings mean for your BOM
The 5 A per channel at 120/230 V AC is a per-point rating, not a group total — each output can switch a load drawing up to 5 A continuously. For a typical 230 V AC contactor coil drawing 0.5 A inrush and 0.1 A hold, that leaves plenty of headroom. The optical isolation means the 24 V DC backplane side is galvanically separated from the AC field side, which simplifies troubleshooting and protects the CPU from field-side transients.
Integration notes
Mounts in any S7-400 rack slot; the backplane connector provides the 24 V DC logic supply and communicates over the P-bus. The field-side wiring terminates on the front connector (screw-type, supplied with the module). The 120/230 V AC outputs share a common supply terminal — verify the neutral and phase assignment against your panel schematic before commissioning.