Isolated Relay Outputs: The Reliable ABB YPO106A​ DO Module

In a water treatment plant’s chemical dosing building, precise control over dozens of solenoid valves for acid, caustic, and polymer injection is critical. These valves operate on 120VAC and are subject to inductive kickback when de-energized, which can damage sensitive electronics. Standard transistor output modules cannot handle this voltage or the inductive loads. Here, the YPO106A​ module is the ideal solution. Installed in an S800 I/O station, each of its 16 relay channels independently switches the 120VAC power to a dosing valve based on commands from the DCS. The relay’s physical isolation completely separates the low-voltage control logic (24VDC on the backplane) from the high-voltage, noisy field circuit. This design directly addresses the pain point of reliably and safely driving real-world industrial loads, protecting the control system from voltage transients and enabling the direct control of high-power devices from a compact, centralized I/O module.