Product Summary
The Allen-Bradley 1794-OA8I Flex I/O module delivers eight individually isolated digital outputs. This unit switches 120V AC loads with a total current rating of 4.0 Amps. Engineers use this output module to connect actuators directly to the PLC logic.
Procurement Guide & Technical Selection
The 1794-OA8I provides eight isolated outputs rated at 120V AC nominal. Each channel supports up to 500 mA of current. This specification makes the module ideal for driving contactors and relays.
The device draws 80mA from the Flexbus at 5V DC. Power dissipation measures 4.1 Watts at 0.5 Amps. Thermal dissipation reaches 14.0 BTU per hour. These values ensure minimal heat buildup in the control cabinet.
The keyswitch on the terminal base must be set to position 8. Compatible bases include the 1794-TB3S, 1794-TB2, 1794-TB3, 1794-TBN, and 1794-TBNF models. Always verify the keyswitch position before installation.
Isolation voltage reaches 120V continuous for channel-to-channel and field-to-backplane. The module withstands 1250V AC for 60 seconds between channels. This isolation protects the control system from ground loops.
The off-state leakage current max is 2.25mA. On-state voltage drop max is 1.0V @ 0.5A. These low values ensure reliable switching of sensitive loads.
The module operates in temperatures ranging from -20 to 55 degrees Celsius. Dimensions are 94 x 94 x 69 millimeters. This compact form factor saves space on the DIN rail.
Step-by-Step Installation & Wiring Guide
First, mount the terminal base onto a standard DIN rail. Hook the base over the top edge of the rail. Push firmly to lock the base into place.
Next, set the keyswitch on the terminal base to position 8. This step matches the module identification for the 1794-OA8I. Insert the module into the base until it clicks securely.
Wire each output to an even-numbered terminal on the base. Connect 120V AC power to the adjacent odd-numbered terminal. Attach individually isolated commons to each output device.
Each output provides a minimum on-state current of 5mA. Use a slow-blow fuse rated at 1.6 Amps, 250 Volts AC. This fuse protects the output circuit from overcurrent faults.
The module uses screw clamp terminals. Tighten each screw to a torque range of 0.56 to 0.79 Nm. Use wire sizes from 22 to 12 AWG for secure connections.
An active output turns the LED indicator yellow on the module face. This visual feedback aids in troubleshooting. Verify each channel by checking the LED status during commissioning.
