1791-OA16 | Allen Bradley | 1791 Block I/O Digital AC Output Module

Product Overview

The Allen Bradley 1791-OA16 provides a high-density, self-contained solution for distributed digital control. As a primary member of the 1791 Block I/O family, this module eliminates the need for a separate rack and power supply, interfacing directly with PLC-2, PLC-3, and PLC-5 processors. We supply this unit as 100% Brand New original stock, offering a vital lifecycle extension for legacy automation systems that require precise 120VAC load switching.

Technical Specifications

The 1791-OA16 utilizes a dual-group architecture to manage 16 independent AC outputs.

Engineering Advantages

• Self-Contained Efficiency: The 1791-OA16 integrates the I/O adapter, power supply, and terminal block into a single footprint. This "Block" design saves significant DIN rail space and reduces the total cost of installation by removing the requirement for an I/O chassis.

• High Surge Handling: Industrial inductive loads like solenoids and motor starters often generate high inrush currents. The 1791-OA16 handles 10A surges for up to 50ms, protecting the internal circuitry while ensuring successful activation of heavy-duty field devices.

• Flexible Mounting Geometry: Engineers can mount the block either vertically or horizontally. This flexibility allows the module to fit into shallow junction boxes or narrow side-panels where traditional rack-mounted I/O cannot go.

• Robust Timing for Synchronized Control: The module achieves a fast turn-on delay of 1.0 ms. For de-energizing, it follows zero-cross principles (8.3ms @ 60Hz), which reduces electrical noise and extends the mechanical life of connected AC actuators.

FAQs

• Can the 1791-OA16 replace a standard 1771 rack-mounted AC output module?

  Functionally, yes. While the 1771 series requires a chassis, the 1791-OA16 performs the same 120VAC output switching but as a standalone block. It communicates via the same Remote I/O (RIO) link, making it an excellent choice for adding points to an existing PLC-5 system without adding a new rack.

• What should I consider regarding the 3mA leakage current?

  Small AC loads, such as high-impedance relays or LED indicators, may remain "ON" due to the 3mA leakage current even when the output is technically "OFF." If using very low-current field devices, install a bleed resistor (load resistor) across the output to ensure the device drops below its holding current.

• Is the external 85-132V AC power required for the logic side or the load side?

  The external power source drives the internal logic and the communication circuitry of the block. You must provide a stable 120VAC source to the power terminals to maintain the RIO link, independent of the voltage applied to the output loads.

• Does this module support individual channel isolation?

  The 16 outputs are organized into two groups of eight. While the groups are isolated from each other, the eight channels within a single group share a common return. Ensure your wiring plan accounts for this shared common to avoid accidental backfeeding.