Allen-Bradley 1746-OA8 SLC 500 Digital AC Output Module

The Allen-Bradley 1746-OA8, also cataloged as the 1746-OA8 SLC 500 discrete AC output module, serves as the primary SLC 500 digital AC output module utilized to execute relayless AC load switching across SLC 500 backplane architectures. Configured for discrete output actuation in SLC 500 chassis systems, the Allen-Bradley 1746-OA8 (1746-OA8 output module) provides direct electrical switching of 85-264 VAC field loads through backplane-controlled triac output stages.

Suffix Breakdown & Model Matrix

No structured suffix segmentation is defined in the supplied documentation. The identifier 1746-OA8 is treated as a fixed SLC 500 module part number without configurable model suffix variants.

Hardware Specifications

SLC 500 Backplane Bus and I/O Density Scaling Behavior

The 1746-OA8 interfaces with the SLC 500 backplane bus through 5 VDC logic-level communication, drawing 185 mA for internal opto-isolated gate drive and triac triggering circuitry. Output density is structured as 8 channels arranged in 2 isolated commons, enabling grouped load referencing across field wiring segments.

Backplane-to-output execution timing is governed by SLC 500 scan cycle synchronization, with discrete ON/OFF transition delays defined by internal optocoupler propagation and triac commutation characteristics. Output switching is non-mechanical and implemented through semiconductor AC switching elements, eliminating relay wear mechanisms while introducing load-dependent turn-off latency.

Frequently Asked Questions (FAQ)

Q: Can the 1746-OA8 be hot-swapped in an energized SLC 500 rack?
A: Hot-swap capability is not defined for this module. Removal or insertion should be performed with chassis power removed to avoid backplane transients.

Q: How is backplane current consumption allocated during operation?
A: The module draws a constant 185 mA @ 5 VDC from the SLC 500 backplane regardless of output state; switching load does not significantly affect logic-side consumption.

Q: What limits the maximum output current per channel?
A: Output current is constrained by triac thermal dissipation and ambient temperature, with derating from 1.0 A at 30 deg C to 0.5 A at 60 deg C.

Field Installation Guidelines

Install the module into a compatible SLC 500 chassis slot with correct backplane alignment to ensure full connector seating. Field wiring must be terminated on the screw terminal block with proper torque control to maintain stable contact resistance under AC switching conditions.

Maintain separation between AC load wiring and low-voltage control conductors to reduce capacitive coupling across channels. Group commons (4 points per group) must be wired according to load reference structure to avoid unintended return path overlap.

Verify isolation between field commons and chassis ground prior to energization. Ensure inductive loads are fitted with appropriate suppression networks to reduce voltage transients during triac turn-off cycles.