Allen-Bradley 1746-OX8 Relay Output Module

Configured for discrete load switching in SLC 500 backplane architectures, the Allen-Bradley 1746-OX8, also cataloged as the 1746-OX8 output module, provides direct electromechanical execution of control signals through isolated relay contacts within an eight-channel output matrix.

Hardware Specifications

Backplane Interface & Isolated Relay Switching (SLC 500 Architecture)

The 1746-OX8 module executes output state transitions through SLC 500 backplane scan cycles, where logic-level commands are translated into relay coil energization events. Each output channel is individually isolated, preventing electrical coupling between field circuits.

Relay contacts provide galvanically separated switching paths for AC and DC loads. The mechanical switching structure introduces a fixed actuation delay, with a maximum 10 ms response for both ON and OFF transitions.

Thermal dissipation is distributed across relay groups, with per-point heat generation contributing to total module thermal load. Terminal block design uses removable screw terminals for discrete field wiring separation.

Hazardous Location Output Isolation Behavior

The module supports operation in Class 1, Division 2 classified environments through inherent relay contact isolation and physical separation of energized circuits. Output channels remain electrically independent, reducing cross-channel conduction paths under mixed AC/DC switching conditions.

Relay contact architecture provides fail-open mechanical state behavior when coil energization is removed, ensuring deterministic output deactivation under loss-of-control conditions. Backplane logic remains electrically segregated from field voltage domains via internal isolation barriers.

Frequently Asked Questions (FAQ)

Q: What is the switching delay of the 1746-OX8 relay outputs?
A: Maximum signal delay is 10 ms for both ON and OFF transitions, determined by mechanical relay actuation time.

Q: Are outputs electrically isolated between channels?
A: Yes, each output is individually isolated using relay contact separation, preventing direct electrical coupling between channels.

Q: Can the module handle both AC and DC loads simultaneously?
A: Yes, the relay contact structure supports mixed AC and DC switching within rated voltage and current limits per channel.

Field Installation Guidelines

The module must be inserted into a powered-down SLC 500 rack to avoid backplane transient states during seating. Screw terminal connections must be tightened to ensure stable contact resistance under vibration conditions.

Field wiring should be separated by voltage class (AC vs DC) to prevent unintended coupling on relay contact outputs. Shielded cable grounding should be terminated at a single-point earth reference within the control cabinet.

Relay load circuits must remain within specified current limits to prevent contact erosion and thermal accumulation at terminal junctions.