Allen-Bradley 1794-OW8XT Relay Output Module for Flex I/O Systems

The Allen-Bradley 1794-OW8XT is a relay output module from the Flex I/O 1794 series. This module has 8 relay output channels that are isolated and normally open. Specifically, the 1794-OW8XT connects different kinds of equipment through several networks. Engineers use this module for switching AC and DC loads in industrial applications.

Output Channel Specifications

The 1794-OW8XT provides 8 relay output channels for flexible control. Each channel is isolated from other channels and the backplane. The contacts are normally open for standard control applications. Multiple networks connect through this versatile module.

Relay Contact Rating

The relay contact rating reaches 250V AC for switching capability. This rating suits many industrial loads. Motors, solenoids, lights, and contactors all connect directly. The minimum contact load reaches 100 µA at 100 mV DC.

Contact Resistance and Bounce Time

The initial contact resistance measures 30 mΩ for efficient current flow. Low resistance minimizes heat generation at the contacts. The bounce time measures 1.2 ms during contact closure. This short bounce time reduces arcing and extends contact life.

Switching Frequency

The maximum switching frequency reaches 1 operation per 3 seconds. This equals 0.3 Hz at rated load for continuous operation. Do not exceed this frequency to avoid overheating. Your application must respect this duty cycle limitation.

Off-State Leakage Current

The off-state leakage current reaches 1.0 mA through the Snubber circuit. This small current flows even when the relay is off. Consider this when switching very sensitive loads. Some devices may not turn off completely with this leakage.

Power Supply Requirements

The supply voltage range spans from 19.2 to 31.2 Volts DC. The nominal voltage is 24 Volts DC for standard operation. The current draw reaches 126 mA for the module logic. Use an external power supply rated for this current.

FlexBus Current and Power Dissipation

The FlexBus current comes from the 5V DC backplane supply. The power dissipation reaches 5.5 W under maximum load. The thermal dissipation reaches 18.8 BTU/hr maximum. Consequently, account for this heat in your enclosure cooling calculations.

Isolation Voltage

The continuous isolation voltage rating reaches 250 Volts. This isolates the relay contacts from the Flex I/O system. Your control circuits remain protected from field wiring faults. Channel-to-channel isolation also applies.

Extended Temperature Operation

The 1794-OW8XT features conformal coating for high temperature operation. This coating protects the circuit board from moisture and contaminants. The module operates at high temperatures without problems. Standard modules may fail under the same conditions.

Terminal Base Compatibility

This module works with 9 different terminal base units available from Allen-Bradley. Choose the base that matches your wiring needs. The terminal base provides screw connections for field wiring. The base also supports daisy-chain power distribution.

Compact Design

The compact design promotes space conservation in your cabinet. The overall size measures 46 mm height, 94 mm width, and 53 mm depth. Multiple modules fit into a small footprint area. The small size allows easy transportation and storage.

Fusing Recommendations

It is recommended to add fusing to the output channels for protection. Fuses prevent damage from overcurrent conditions. Size fuses according to your connected load requirements. Each output channel should have its own fuse.

Grounding Requirements

When installing this module, ground it through the DIN rail. Use a zinc-plated yellow-chromate steel DIN rail for installation. Other materials may cause improper or intermittent grounding. The module needs a reliable ground path for proper operation.

Step-by-Step Installation Guide

Follow these steps to install your Allen-Bradley 1794-OW8XT correctly.

Step 1: Select the Terminal Base
First, choose a compatible terminal base for relay outputs. Nine different terminal base units work with this module. Mount the terminal base on DIN rail securely. Use zinc-plated yellow-chromate steel DIN rail for proper grounding.

Step 2: Set the Keyswitch
Next, locate the keyswitch on the 1794-OW8XT module. Set the keyswitch to the correct position for this module type. This prevents incorrect insertion into the wrong slot. Verify the keyswitch is fully engaged before proceeding.

Step 3: Install the Module
Now, insert the 1794-OW8XT into the mounted terminal base. Push firmly until the module seats completely. The locking mechanism should click into place. Ensure the module sits flush with adjacent units.

Step 4: Connect Field Wiring
Wire your field devices to the terminal base screw terminals. Connect each load to the appropriate relay output channel. The contacts are normally open and rated for 250V AC. Install fuses on each output channel for overcurrent protection.

Step 5: Connect External DC Power
Wire the 24V DC external power supply to the terminal base. The voltage range accepts 19.2 to 31.2V DC. Ensure the supply can provide at least 126 mA for the module logic. Verify polarity is correct before applying power.

Step 6: Test Output Operation
Apply power to the Flex I/O system and the external supply. Turn on each output channel from your controller. Verify the relay clicks and the load energizes. Turn off each output and verify the load de-energizes. Check that the off-state leakage current does not affect sensitive loads.

Complete Package Contents

Your Allen-Bradley 1794-OW8XT shipment includes the following items:

• Allen-Bradley 1794-OW8XT Relay Output Module (1 unit)

• Product documentation and installation manual

• Module labeling sheet for channel identification

• Keyswitch adjustment tool

Note: Shipping partners include FedEx, UPS, and DHL.

Frequently Asked Questions (FAQ)

Q1: How many relay outputs does the 1794-OW8XT provide?
The 1794-OW8XT provides 8 isolated relay output channels. Each channel has normally open contacts. The contacts are rated for 250V AC switching.

Q2: What is the switching frequency limitation of the 1794-OW8XT?
The maximum switching frequency reaches 1 operation per 3 seconds (0.3 Hz at rated load). Do not exceed this frequency to avoid overheating. Your application must respect this duty cycle limitation.

Q3: Is fusing required for the 1794-OW8XT output channels?
It is recommended to add fusing to each output channel for protection. Fuses prevent damage from overcurrent conditions. Size fuses according to your connected load requirements.

Q4: What is the off-state leakage current of the 1794-OW8XT?
The off-state leakage current reaches 1.0 mA through the Snubber circuit. This small current flows even when the relay is off. Consider this when switching very sensitive loads.

Q5: What grounding method is recommended for the 1794-OW8XT?
Ground the module through the DIN rail during installation. Use a zinc-plated yellow-chromate steel DIN rail for proper grounding. Other materials may cause improper or intermittent grounding.