What Is the 1746-OA8?
The Allen-Bradley 1746-OA8 is an SLC 500 discrete AC output module from Rockwell Automation. It provides eight output channels arranged in two groups of four, giving you flexible control over AC-powered field devices. Each group operates independently, which simplifies wiring and lets you isolate circuits when needed.
This module fits directly into an SLC 500 chassis and draws 185 mA from the 5 VDC backplane. It handles a nominal output voltage of 120 or 240 VAC, with an actual output voltage range of 85-264 VAC. That wide range means the same module works across common industrial AC supplies without extra conditioning. If you maintain legacy SLC 500 systems, the 1746-OA8 remains a practical drop-in solution for AC output tasks.
Technical Specifications That Matter
Output Voltage Range
The 85-264 VAC range covers both 120 VAC and 240 VAC nominal systems. You can drive solenoids, relays, and indicator lamps on either supply without swapping hardware. The module also tolerates normal line fluctuations, which reduces nuisance faults in plants with less-than-perfect power quality.
Channel Configuration
Eight channels in two groups of four give you a balance between density and isolation. If one group fails, the other four channels keep working. This grouping also makes troubleshooting faster because you can test each bank separately.
Current Capacity
Each point carries 1.00 A at 30 °C and 0.5 A at 60 °C. The module as a whole handles 8.0 A at 30 °C and 4.0 A at 60 °C. These ratings let you drive small contactors and pilot devices directly, but you should total your load current carefully before connecting high-inrush devices.
Switching Speed
The 1746-OA8 turns on in 1 ms maximum and turns off in 11 ms maximum with a resistive load. Fast ON response suits applications that need quick actuation, while the slower OFF time is typical for AC output modules and rarely causes issues in general-purpose control.
Where the 1746-OA8 Fits Best
General Purpose Control
Machine builders use this module for indicator lamps, small relays, and solenoid valves. The wide voltage range means one spare part covers multiple machine designs, which cuts inventory costs.
Legacy SLC 500 Upgrades
When an existing 1746-OA8 fails, replacing it keeps the rest of the SLC 500 rack running. This avoids a full controller migration and protects your original automation investment.
Mixed-Voltage Panels
Panels that run some devices at 120 VAC and others at 240 VAC can use the same module type throughout. That simplifies spare parts planning and reduces training time for maintenance staff.
Installation and Setup
Mount the module in a compatible SLC 500 chassis and secure it properly. Connect field wiring to the output terminals according to your panel drawings. Keep AC output wiring separated from low-level signal cables to reduce electrical noise. Verify that the backplane supply can provide the 185 mA current draw before you power up the rack. Always follow local electrical codes and the manufacturer’s installation instructions.
Maintenance and Reliability
Inspect terminal connections periodically for tightness and signs of heat damage. Check for dust buildup on the module face and clean only with methods approved for industrial control equipment. Because the module uses solid-state outputs, there are no moving parts to wear out. The main wear points are the field wiring terminations and the loads themselves. Replace the module if you see stuck outputs or intermittent channel behavior.
Compatibility and Integration
The 1746-OA8 works within the SLC 500 platform and connects to the backplane for logic power and data. It integrates with SLC 500 processors and I/O adapters that support the 1746 series. If you are unsure whether your existing rack supports this module, check your chassis and processor documentation before ordering.
Selection Guide
Before buying a 1746-OA8, confirm your output voltage, total current per group, and ambient temperature. Verify that your chassis has an open slot and that your power supply can handle the added 185 mA backplane load. If you need a reliable source for this module, SpareTechPLC offers industrial automation parts and support. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
Can the 1746-OA8 drive both 120 VAC and 240 VAC loads?
Yes. The output voltage range is 85-264 VAC, so it supports both nominal voltages in the same module.
How many outputs does this module have?
It has eight outputs, split into two groups of four channels each.
What is the maximum current per point?
Each point handles 1.00 A at 30 °C and 0.5 A at 60 °C. Total module current is 8.0 A at 30 °C and 4.0 A at 60 °C.
How fast does the module switch?
Maximum ON delay is 1 ms and maximum OFF delay is 11 ms with a resistive load.
What backplane current does it require?
The module draws 185 mA from the 5 VDC backplane.
