1746-OW8/A | Allen-Bradley 8-Ch Relay Output Module

Product Overview: 1746-OW8/A Relay Output Module

When a control panel must switch mixed AC and DC field loads from a single SLC 500 rack, electromechanical isolation becomes the deciding factor. The Allen-Bradley 1746-OW8/A solves this by providing eight normally-open relay outputs, arranged as two groups of four, with contacts rated for 5-265 VAC or 5-125 VDC. Each output carries 1.5 A at 120 VAC or 1.2 A at 24 VDC, while each common supports 8 A continuous and the module supports 16 A continuous overall. Because the contacts are dry relay elements, the module interfaces directly with motor starters, solenoids, pilot devices, alarms, and interposing relays without external signal conditioning.

Key Specifications of the 1746-OW8/A

• Output type: 8 normally-open relay contacts, 2 groups of 4
• Operating voltage: 5-265 VAC or 5-125 VDC
• Current rating: 1.5 A per output at 120 VAC; 1.2 A at 24 VDC
• Common rating: 8 A continuous per common; 16 A per module
• Backplane draw: 85 mA at 5V DC and 90 mA at 24V DC
• Signal delay: 10 ms ON / 10 ms OFF
• Isolation: 1500 VAC contacts to backplane
• Mounting: 1746 I/O chassis, open-style

The 1500 VAC contact-to-backplane isolation is the defining parameter. It prevents field transients from motor starters and solenoids from coupling into the SLC 500 logic bus, protecting the processor and adjacent modules.

Installation and Wiring Practice

Because the 1746-OW8/A is not hot-swappable, always remove chassis power before installation, removal, or field wiring. Slot 0 remains reserved for the processor or a 1747-ASB adapter. Field-side load power requires an external supply; the backplane provides logic power only. Removable terminal blocks simplify field termination, and Bulletin 1492 pre-wired interface cables are available for panel builds. For engineering-grade precision in high-vibration panels, verify terminal torque and conductor seating after commissioning.

Reliability and Lifecycle Status

Relay contacts are wear items. In high-cycle applications, inspect contact resistance periodically and replace the module when pitting or welding appears. The 0 to 60 C operating range and 5-95% RH non-condensing rating suit typical factory environments. Note that the 1746-OW8/A is discontinued as of 2022-12-31, with Rockwell recommending migration to Compact 5000 I/O on the Logix platform. Please verify current lifecycle status and availability with AutoDCSTech before ordering.