1746-OA8 Allen-Bradley 8-Channel AC Output

1746-OA8 Allen-Bradley 8-Channel AC Output Module

Product Introduction

The Allen-Bradley 1746-OA8 offers a reliable and cost-effective solution for controlling AC loads within the SLC500 system. This module provides eight independent output channels, organized into two isolated groups of four. It handles nominal voltages of 120 or 240 VAC, with a broad operational range from 85 to 264 VAC. Therefore, it adapts easily to varying power conditions worldwide. Compared to its 16-channel counterpart, the 1746-OA8 delivers higher current per point. Each channel supports up to 1.0 A continuously at 30 °C. This makes it particularly suitable for driving larger contactors, solenoids, and pilot lights.

Technical Specifications

Output Capacity and Current Ratings
The 1746-OA8 features eight AC outputs arranged in two groups, with four channels per group. Each output handles a continuous current of 1.00 A at 30 °C (86 °F). At 60 °C (140 °F), this rating derates to 0.50 A per point. The total module current reaches 8.0 A at 30 °C, reducing to 4.0 A at 60 °C for thermal protection. Additionally, each point withstands a surge current of 10.0 A for 25 milliseconds. This surge capability handles the inrush current typical of inductive loads like motor starters. The on-state voltage drop measures a maximum of 1.5 V at 1.0 A, minimizing heat generation.

Timing and Switching Performance
This module exhibits fast and predictable switching behavior. The ON signal delay is just 1 ms for resistive loads, while the OFF signal delay measures 11 ms. These response times suit most general-purpose control applications. Furthermore, the step response is 60 ms in and 2.5 ms out, ensuring stable output transitions. The OFF-state leakage current stays low, preventing unintended activation of sensitive loads.

Power Consumption
The 1746-OA8 draws only 185 mA from the 5 VDC backplane. This low consumption makes it an energy-efficient choice for your SLC500 chassis. Consequently, you can install multiple modules without overloading the system power supply. Always verify total backplane current against your power supply's capacity during system design.

Mechanical and Environmental Parameters

Physical Design
This module occupies a single slot in the SLC500 chassis. Its compact size allows efficient use of rack space. The removable terminal blocks simplify wiring and maintenance. You can replace the module quickly without disconnecting field wires. This feature significantly reduces downtime during troubleshooting or upgrades.

Environmental Specifications
The Allen-Bradley 1746-OA8 operates reliably in temperatures from 0 °C to 60 °C (32 °F to 140 °F). It also tolerates relative humidity between 5% and 95%, non-condensing. These specifications make it suitable for demanding factory floor environments. Ensure proper airflow around the module for optimal thermal management.

Installation and Integration Guide

Mounting Procedure
First, confirm your chassis power supply can accommodate the additional 185 mA backplane load. Then, select an available slot in the SLC500 rack. Insert the 1746-OA8 carefully, aligning it with the backplane connector. Press firmly until the module seats completely. Finally, secure it with the retaining screws to prevent loosening from vibration.

Wiring Recommendations
Connect your AC loads to the appropriate terminals on the removable connectors. Each group of four outputs shares a common terminal. You can power each group from different AC sources if required. However, ensure each source stays within the 85-264 VAC range. Use properly sized conductors for the expected load currents. For inductive loads, consider installing snubber circuits across the load terminals to reduce electrical noise and extend contact life.

Programming and Addressing
The 1746-OA8 occupies 8 bits of the output image table in your SLC500 processor. Each channel maps to a specific bit address. You control outputs using standard ladder logic instructions like OTE (Output Energize) or OTU (Output Unlatch). The module's front panel features LED indicators for each channel. These provide immediate visual feedback on output status, simplifying field troubleshooting.

Packaging List

• Allen-Bradley 1746-OA8 Discrete AC Output Module (1 unit)

• Removable terminal block connectors (2 units, 4 positions each)

• Quick-start installation guide

Note: Cables, programming software, and mounting hardware are not included.

Shipping Information

All orders ship via FedEx, UPS, or DHL with tracking numbers provided. Please ensure your shipping address and contact details are correct for prompt delivery.

Frequently Asked Questions

1. What is the main difference between the 1746-OA8 and the 1746-OA16?
The 1746-OA8 has 8 outputs with a higher current rating of 1.0 A per point. The 1746-OA16 offers 16 outputs but each point supports only 0.5 A. Choose the 1746-OA8 when you need to drive heavier AC loads.

2. Can I mix 120V and 240V loads on the same module?
Yes, you can. Each group operates independently, so one group can run at 120 VAC while the other runs at 240 VAC. However, all outputs within the same group must share the same voltage source.

3. Does the 1746-OA8 provide short-circuit protection?
No, this module does not include built-in short-circuit protection. You should install external fuses or circuit breakers on each output channel to protect against overcurrent faults.

4. How do I know if the module is working correctly?
Each output channel has a green LED indicator on the front panel. When the processor energizes an output, the corresponding LED turns on. This allows quick visual verification without connecting a programming terminal.

5. Is this module compatible with newer ControlLogix systems?
Yes, the 1746-OA8 can be used with ControlLogix or CompactLogix systems via a 1746 remote I/O adapter or a 1756-DHRIO module. This provides flexibility when migrating from SLC500 to newer platforms.