Allen-Bradley 1756-OA8D – ControlLogix Diagnostic AC Output Module

The Allen-Bradley 1756-OA8D is a ControlLogix diagnostic AC output module. Specifically, this module provides 8 diagnostic outputs for AC load control. It operates at 120 Volts AC with a voltage range of 74-132 Volts AC. Furthermore, each output is electronically fused for protection. In addition, this module mounts in any slot of the 1756 ControlLogix chassis. Consequently, it suits applications requiring output diagnostics and electronic fuse protection.

Ordering Configuration and Product Identification

• Manufacturer: Rockwell Automation.

• Brand: Allen-Bradley.

• Part Number: 1756-OA8D.

• Series: ControlLogix.

• Module Type: Diagnostic AC Output Module.

• Number of Outputs: 8 diagnostic outputs.

• Voltage Rating: 120 Volts AC.

• Operating Voltage Range: 74 to 132 Volts AC.

• Frequency Range: 47 to 63 Hz.

• UPC: 10612598164520.

• Therefore, the Allen-Bradley 1756-OA8D accepts standard industrial AC voltages.

Output Current Ratings

• Maximum Current per Point (30°C): 1 Amp.

• Maximum Current per Point (60°C): 0.5 Amps.

• Maximum Current per Module (30°C): 8 Amps.

• Maximum Current per Module (60°C): 4 Amps.

• Derating: Linear derating between 30°C and 60°C.

• Maximum Surge Current: 8 Amps for 43 ms per point.

• Surge Repetition: Recurring every 2 seconds at 30°C.

• Minimum Load per Point: 10 mA.

• Leakage Current (OFF State): 3 mA per point maximum.

• Maximum Drop Voltage: 3.0 Volts at 1.0 Amp.

• Thus, the 1756-OA8D supports moderate current loads with surge capability.

Output Delay Times

• ON/OFF Delay (50 Hz): 9.3 milliseconds maximum.

• OFF/ON Delay (50 Hz): 9.3 milliseconds maximum.

• ON/OFF Delay (60 Hz): 11 milliseconds maximum.

• OFF/ON Delay (60 Hz): 11 milliseconds maximum.

• Frequency Dependence: Delay varies with line frequency.

• Application Consideration: Suitable for most industrial switching applications.

• Consequently, the Allen-Bradley 1756-OA8D provides predictable switching performance.

Backplane Current and Power Specifications

• Backplane Current (5.1 Volts DC): 175 milliamps.

• Backplane Current (24 Volts DC): 250 milliamps.

• Power Dissipation (Max): 5.3 Watts at 60°C.

• Power Dissipation (Gross Backplane): 6.9 Watts.

• Thermal Dissipation: 18.0 BTU per hour.

• Isolation Voltage (Continuous): 50 Volts (spec sheet), 125 Volts (description).

• Isolation Test (Outputs to Backplane): 1200 Volts AC for 2 seconds.

• Isolation Test (Group to Group): 1200 Volts AC for 2 seconds.

• Isolation Between Individual Outputs: None within same group.

• Enclosure Type: None (open-style, requires chassis).

• Weight: Approximately 1.0 kg (2.25 lbs).

• Therefore, the 1756-OA8D requires adequate chassis cooling for full load operation.

Diagnostic Features

• Output Type: Diagnostic outputs with electronic fusing.

• Fuse Type: Electronically fused (no physical fuse replacement).

• Diagnostic Capability: Monitors output status and faults.

• Fault Indication: Reports short circuits and overloads.

• Benefit: Reduces downtime with fast fault detection.

• Reset Method: Software-controlled or power cycle.

• Module Width: Single slot.

• Keying: User-discretionary on removable terminal block.

• Designation Code: T4A.

• Thus, the Allen-Bradley 1756-OA8D enables rapid fault diagnosis without replacing fuses.

Removable Terminal Block Options

• Compatible RTB 1: 1756-TBNH.

• Compatible RTB 2: 1756-TBSH.

• Terminal Block Type: Removable for easy wiring.

• Wiring Benefit: Simple module replacement without rewiring.

• Keying: User-configurable for error prevention.

• Field Wiring: Standard AC wiring practices.

• Maintenance: Reduced downtime during module exchange.

• Therefore, the 1756-OA8D simplifies installation and maintenance.

Temperature and Environmental Ratings

• Operating Temperature Range: 0°C to 60°C (32°F to 140°F).

• Optimal Temperature Range: 0°C to 60°C.

• Relative Humidity: 5% to 95% non-condensing.

• Enclosure Rating: Open-style (install in ControlLogix chassis).

• Chemical Resistance: Avoid direct chemical exposure.

• Vibration: Standard ControlLogix ratings.

• Shock: Standard ControlLogix ratings.

• Moreover, the Allen-Bradley 1756-OA8D withstands typical industrial environments.

Installation Guide

First, verify that all system power sources are completely disconnected. Then, select an available slot in your 1756 ControlLogix chassis. The Allen-Bradley 1756-OA8D occupies a single slot. After that, slide the module into the chosen slot. Push firmly until the backplane connector is fully seated. Next, select your removable terminal block (1756-TBNH or 1756-TBSH). Then, wire your AC loads to the terminal block following the pinout diagram. Connect the AC supply (74-132V AC, 47-63 Hz) to the appropriate terminals. Ensure that each output's load does not exceed the current ratings. For temperatures above 30°C, apply linear derating to the load current. Then, install the terminal block onto the module front. Secure it using the provided latches. After that, apply power to the ControlLogix chassis. The module will begin its power-up sequence. Then, configure the diagnostic output parameters using Studio 5000 software. Enable electronic fuse monitoring as required. Finally, test each output channel under load. As a result, the Allen-Bradley 1756-OA8D will provide reliable AC output control with diagnostic feedback.

Packaging List

• One Allen-Bradley 1756-OA8D ControlLogix diagnostic AC output module

• One product identification label

• One installation and configuration guide

• Removable terminal block (purchased separately: 1756-TBNH or 1756-TBSH)

Common FAQs

Q1: How many outputs does the Allen-Bradley 1756-OA8D provide?
A: This module provides 8 diagnostic AC outputs. Each output is electronically fused for protection. Therefore, no physical fuse replacement is needed.

Q2: What is the voltage range for the 1756-OA8D?
A: The operating voltage range is 74 to 132 Volts AC at 47-63 Hz. The nominal voltage is 120 Volts AC. Therefore, it suits standard North American AC control circuits.

Q3: What is the maximum current per output on the Allen-Bradley 1756-OA8D?
A: At 30°C, the maximum current is 1 Amp per point. At 60°C, the maximum current is 0.5 Amps per point. Consequently, linear derating applies between these temperatures.

Q4: What removable terminal blocks are compatible with the 1756-OA8D?
A: The 1756-TBNH and 1756-TBSH terminal blocks are compatible. Both types are removable for easy wiring. Therefore, module replacement does not require rewiring.

Q5: Does the 1756-OA8D have isolation between individual outputs?
A: No, there is no isolation between individual outputs within the same group. However, isolation exists between output groups and the backplane. Isolation is tested at 1200V AC for 2 seconds.