Allen-Bradley 1756-OA8D ControlLogix Diagnostic Output Module

The Allen-Bradley 1756-OA8D is a ControlLogix 120V AC diagnostic output module designed for high-reliability industrial automation environments. Operating as an 8-point electronically fused output device, it provides comprehensive point-level diagnostic detection—including open wire, field power loss, blown fuse, no load, and output verification faults—to ensure optimal operational integrity across PLC, DCS, and automated process control systems.

Description

The Allen-Bradley 1756-OA8D ControlLogix output module delivers solid-state switching for 120V AC field devices. Operating within a voltage range of 74 to 132V AC (47 to 63 Hz), the module features 8 diagnostic output points arranged in two groups of 4 points. It utilizes Producer/Consumer technology to share output status and comprehensive diagnostic data seamlessly across the ControlLogix backplane.

Engineered for critical industrial applications, the 1756-OA8D provides advanced diagnostic reporting to identify field wiring issues, short circuits, or power disruptions. Off-state detection identifies no-load conditions, while on-state output verification ensures commanded states match actual field conditions. Individual electronic fusing helps protect each output point against overcurrent and short-circuit events.

Features

• 8 diagnostic output channels organized into 2 isolated groups of 4 points each.
• Point-level diagnostic features including FuseBlown, NoLoad, OutputVerifyFault, and FieldPwrLoss.
• Individual electronic fusing per output point.
• Configurable output states in Program Mode and Fault Mode (Hold Last State, On, or Off).
• Coordinated System Time (CST) timestamping for diagnostic event tracking.
• Support for Scheduled Outputs with CST synchronization.
• Electronic keying via software configuration to prevent module misplacement.

Applications

• Discrete AC actuator and valve control
• Motor starter and contactor switching
• Industrial process output control
• Safety signaling and indicator control
• Automated manufacturing systems

Technical Specifications

Installation Guidelines

• Chassis Mounting: Install the module into any available slot in a 1756 ControlLogix chassis.
• Terminal Block Compatibility: Use designated Removable Terminal Blocks (1756-TBNH or 1756-TBSH) for field wiring connections.
• Wiring Specifications: Ensure field wiring uses single wire connections of 0.33…2.1 mm2 (22…14 AWG) or double wire connections of 0.33…1.3 mm2 (22…16 AWG) solid/stranded shielded copper wire rated at 105 degC or higher.
• Conductor Category: Follow Wire Category 1 routing recommendations on signal ports according to industrial wiring and grounding guidelines.
• System Derating: When operating in extended or harsh environment systems, ensure all paired chassis and power supply components match the required thermal specifications.

Compliance and Certifications

• cULus: UL Listed Industrial Control Equipment, certified for US and Canada (UL File E65584); UL Listed for Class I, Division 2 Group A,B,C,D Hazardous Locations (UL File E194810).
• CE: European Union 2014/30/EU EMC Directive (EN 61326-1, EN 61000-6-2, EN 61000-6-4, EN 61131-2) and 2014/35/EU LVD Directive (EN 61131-2).
• RCM: Australian Radiocommunications Act, compliant with EN 61000-6-4.
• FM: FM Approved Equipment for use in Class I Division 2 Group A,B,C,D Hazardous Locations.
• KC: Korean Registration of Broadcasting and Communications Equipment.
• UKCA: Compliant with UK Statutory Instruments for EMC, Safety, Explosive Atmospheres, and RoHS.
• Morocco: Compliant with ministerial order regulations for electrical safety and EMC.