Allen-Bradley 1746-OA8 AC Output Module

Allen‑Bradley 1746‑OA8 AC Output Module

The Allen‑Bradley 1746‑OA8, also cataloged as the 1746‑OA8 AC output module, provides deterministic 120/240 VAC output actuation for SLC 500 platforms. The module executes fixed‑delay switching, backplane‑powered logic interfacing, and per‑point current handling across eight output channels.

Hardware Specifications

Backplane Bus Timing and Output Determinism

Within SLC 500 architectures, the 1746‑OA8 participates in deterministic backplane bus arbitration, ensuring predictable output‑update timing relative to the processor scan. The 185 mA load at 5 VDC influences overall I/O density scaling, especially when multiple high‑current modules coexist. Output transitions follow fixed AC‑cycle‑dependent timing, and the OFF‑state leakage of 2 mA must be considered when driving high‑impedance loads.

Frequently Asked Questions

Q: Can the 1746‑OA8 be hot‑swapped in a powered SLC chassis A: No. The module must be inserted or removed only when the chassis is de‑energized to avoid backplane faults.

Q: Does the module support DC loads A: No. The 1746‑OA8 is designed exclusively for AC output operation.

Q: How does temperature affect current ratings A: Continuous current capacity decreases from 1.0 A per point at 30 °C to 0.50 A per point at 60 °C.

Field Installation Guidelines

Maintain proper conductor sizing for 120/240 VAC loads. Route AC wiring separately from low‑level analog circuits to reduce noise coupling. Ensure terminal screws are torqued according to SLC wiring standards. Verify that load devices meet the minimum 10 mA current requirement to prevent false OFF states. Confirm backplane power capacity when installing multiple AC output modules.