Allen-Bradley 1794-OA8 120V AC Output Module

1794-OA8 Flex I/O 8-Channel AC Digital Output Module

Product Introduction

The Allen‑Bradley 1794‑OA8 module offers a compact and efficient solution for controlling AC loads in distributed I/O systems. This digital output module features eight non-isolated output channels that operate within an 85-132VAC range at 47-63 Hz. It interfaces seamlessly with any Flex I/O communication adapter and supports installation in Class I, Division 2 hazardous locations. Moreover, the module provides diagnostic capabilities that help identify issues with field devices, wiring, and power supplies, significantly reducing start‑up time and maintenance efforts.

Technical Specifications

The 1794‑OA8 module delivers consistent output performance across its operating range. Its output voltage spans from 85VAC minimum to 132VAC maximum, with a nominal rating of 120VAC. Total output current reaches 4.0 A, distributing across the 8 channels. Each output channel can handle 500 mA continuously at 55°C. Furthermore, the module offers higher current capacities at lower temperatures: 750 mA per output at 35°C, and 1 A on four non-adjacent outputs at 30°C.

For transient loads, the 1794‑OA8 provides a surge current rating of 7 A for 40 ms, repeatable every 8 seconds. On‑state voltage drop measures a maximum of 1.0 V at 0.5 A, while off‑state leakage current stays below 2.25 mA. Minimum on‑state current per output is 5 mA. Additionally, the module exhibits a maximum output signal delay of one‑half cycle for both OFF‑to‑ON and ON‑to‑OFF transitions.

FlexBus current draw for the 1794‑OA8 reaches 80 mA at 5V DC. Maximum power dissipation measures 4.1 W at 0.5 A, 6.3 W at 0.75 A, and 6.3 W at 1.0 A. Correspondingly, thermal dissipation reaches 14.0 BTU/hour at 0.5 A, 21.2 BTU/hour at 0.75 A, and 21.4 BTU/hour at 1.0 A. Isolation voltage stands at 120V continuous.

Environmental and Hazardous Location Ratings

The 1794‑OA8 module suits a wide range of industrial environments. It operates reliably in temperatures from 0°C to 55°C (32°F to 131°F) with 5-95% non‑condensing humidity. Storage temperatures range from -40°C to 85°C (-40°F to 185°F). For mechanical durability, the module withstands 5G vibration at 10-500 Hz and operating shocks of 30G.

Notably, the 1794‑OA8 carries approval for Class I, Division 2 hazardous locations, making it suitable for environments with potentially flammable gases or vapors. This feature expands its application scope beyond standard industrial settings. ESD immunity requirements of 8 kV for air discharges are also met.

Mounting Base Compatibility

The 1794‑OA8 connects to field wiring through a compatible 1794 terminal base unit. It works with the following base models: 1794‑TBN, 1794‑TBNF, 1794‑TB2, 1794‑TB3, 1794‑TB3S, 1794‑TBKD, 1794‑TBNK, 1794‑TBNFK, 1794‑TB3K, and 1794‑TB3SK. For the 1794‑TBN base, auxiliary terminal strips are essential to connect the 120V AC common voltage source for individual channels. Meanwhile, the 1794‑TBNF base includes integrated fusing for added protection.

Installation Guidelines

Installing the 1794‑OA8 correctly ensures safe and reliable operation. First, set the keyswitch on the terminal base to position 8, the designated setting for this module. Next, push the Flexbus connector fully to the left to establish a connection with the adjacent adapter or base.

Then, align the module's groove with the alignment bar on the terminal base. Press the module straight inward until the latching mechanism clicks securely into place. For wiring, connect each AC load to the appropriate output terminals according to your terminal base type. Also, connect the AC common and power supply leads as specified in the terminal base documentation. Note that the outputs are not individually fused on the module itself, so you may need to use the 1794‑TBNF base or external fuses for point‑level protection.

Packaging List

Your shipment for the 1794‑OA8 includes the following items:

• (1) Allen‑Bradley 1794‑OA8 Digital Output Module

Frequently Asked Questions (FAQ)

Q1: What types of loads can I control with the 1794‑OA8 module?
A1: This module drives AC loads such as relay coils, solenoid valves, contactors, pilot lights, horns, and other devices that operate at 120V AC nominal voltage.

Q2: What is the maximum current per output channel on the 1794‑OA8?
A2: The maximum current depends on temperature. 55°C, each output supports 500 mA. 35°C, it increases to 750 mA per output. 30°C, you can draw 1 A on four non-adjacent outputs.

Q3: Which terminal base units work with the 1794‑OA8?
A3: This module fits the 1794‑TBN, 1794‑TBNF, 1794‑TB2, 1794‑TB3, 1794‑TB3S, 1794‑TBKD, 1794‑TBNK, 1794‑TBNFK, 1794‑TB3K, and 1794‑TB3SK bases. Choose the base that matches your wiring and fusing requirements.

Q4: Can I install the 1794‑OA8 in a hazardous location?
A4: Yes, this module carries Class I, Division 2 certification, making it suitable for use in areas with flammable gases or vapors. Always follow local installation codes and guidelines.

Q5: Does the 1794‑OA8 provide individual output fusing?
A5: No, the module itself does not include per‑point fusing. However, you can use the 1794‑TBNF terminal base, which integrates fusing, or add external fuses for each output channel.