AS-i ground fault detection — what it does on the line
The 3RK1408-8KE00-0AA2 is an AS-Interface ground fault detection module that monitors one input and provides two signaling outputs via a relay rated DC-12 1 A or DC-13 500 mA at 24 V. It does not require its own AS-i address, so it fits onto an existing segment without consuming node capacity — useful for adding diagnostic coverage to a populated AS-i network. The module detects an earth fault when the ground voltage falls between 10% and 90% of the AS-i supply voltage (Uas-i). It does not perform overvoltage detection, and it has no counter function — its job is purely ground-fault annunciation for the segment. Siemens notes that if repeaters are used, a separate ground fault detection module is required per AS-i segment (one per power supply unit). The auxiliary supply (Uaux) should be protected by a 2 A slow-blow fuse, and inductive loads on the relay should include freewheel diodes to extend contact endurance.
Lifecycle status — NRND, sourcing path
This module carries a lifecycle status of NRND (Not Recommended for New Designs). That means Siemens will continue to support existing installations but is steering new projects toward a current alternative. For BOM lines already in production, the module remains orderable through independent distribution — quoted to order against the RFQ, with availability confirmed at quote time. No official successor order code is listed by Siemens. If you are evaluating a replacement for a new panel, contact us with the application details and we can review the functional requirements against the current AS-i portfolio.
Mounting and connections — DIN-rail footprint
The module measures 22.5 mm wide, 102 mm high, and 86 mm deep — a standard S22.5 housing that snaps onto a 35 mm DIN rail or mounts directly to a panel. Protection class is IP20, so it belongs inside a cabinet, not in a washdown zone. Connections are via screw-type terminals for the inputs and outputs. The AS-i connection includes built-in polarity reversal protection, which simplifies wiring and avoids a common commissioning error. Operating temperature range is -25 to +70 °C, with storage from -40 to +85 °C. The relay is rated for 2,000,000 operating cycles under DC-12 load.