1756-OX8I | Allen-Bradley Isolated Relay Output Module Supplier

Product Overview: The 1756-OX8I Isolated Relay Output Module

When your control system requires dependable switching for multiple voltage types, the 1756-OX8I provides a robust solution. This Allen-Bradley module is part of the ControlLogix series and functions as an isolated relay output module. It features eight individually isolated outputs, each with Form C contacts, allowing you to connect loads operating at different voltage levels. The module supports AC voltages from 10 to 265 VAC and DC voltages from 5 to 150 VDC, making it versatile for various industrial applications.

Key Features & Technical Specifications

• The 1756-OX8I offers 8-point individually isolated outputs for independent channel operation.
• Each output uses Form C contacts, providing both normally open (N.O.) and normally closed (N.C.) configurations.
• Operating voltage ranges from 10-265 VAC and 5-150 VDC, accommodating mixed-voltage loads.
• Output current ratings are 2, 0.5, and 0.25 Amps, depending on the load type.
• Maximum switching frequency is 1 operation per 3 seconds (0.3 Hz at rated load).
• Initial contact resistance is 100 mΩ at 6V and 1A.
• Expected contact life reaches 300 kHz for resistive loads and 100 kHz for inductive loads.
• Backplane current draw is 100 mA at 5 Volts, with maximum power dissipation of 3.1 Watts at 60°C.

A distinctive spec is the isolation voltage of 250V continuous, basic insulation type, applied between outputs and backplane and between output-to-output. This ensures safe operation even when channels are wired to different voltage sources.

Applications & Use Cases

In manufacturing lines, the 1756-OX8I excels at switching contactors, motor starters, and pilot lamps. Because each output is individually isolated, you can mix AC and DC loads without concern. For example, one channel might control a 120 VAC motor starter while another switches a 24 VDC indicator light. This flexibility reduces the need for additional interface modules. Furthermore, the module's Form C contacts support both normally open and normally closed wiring, simplifying integration with existing safety circuits.

Installation & Setup

Mount the 1756-OX8I directly into a 1756 local or remote chassis. Use a compatible removable terminal block (RTB) such as the 1756-TBCH or 1756-TBS6H (sold separately). These RTBs simplify wiring and allow quick module replacement without disturbing field wiring. For non-isolated operation, you can short the L1 connections using a 1756-JMPR jumper or a third-party conductor. Always follow the manufacturer's manual for proper wiring and torque specifications.

Maintenance & Reliability

To maximize the 1756-OX8I's service life, inspect the module periodically for signs of wear or contamination. The expected contact life of 300 kHz resistive and 100 kHz inductive means the module can handle millions of cycles under normal conditions. Keep the enclosure free of dust and moisture, as the module has no built-in enclosure (rated as None). Regular inspection per the manufacturer's guidelines helps prevent unexpected downtime.

Compatibility & Integration

The 1756-OX8I is designed for the ControlLogix platform and works with any 1756 local or remote chassis. It communicates via the backplane, drawing 100 mA at 5 Volts. The module is compatible with standard ControlLogix I/O configurations and can be used with various controllers in the family. For wiring, use the specified removable terminal blocks (1756-TBCH or 1756-TBS6H) to ensure proper connection.

Troubleshooting & Common Issues

If an output fails to switch, first verify the wiring and terminal block connection. Check that the operating voltage is within the 10-265 VAC or 5-150 VDC range. The maximum output delay time is 13 milliseconds, so if switching seems slow, confirm the load is not exceeding the rated current. For intermittent operation, inspect the contacts for wear or contamination. Refer to the official Allen-Bradley documentation for detailed diagnostics.

FAQ about 1756-OX8I

Q: What is the maximum switching frequency of the 1756-OX8I?

A: The maximum switching frequency is 1 operation per 3 seconds (0.3 Hz at rated load).

Q: Can the 1756-OX8I handle both AC and DC loads?

A: Yes, it supports AC voltages from 10-265 VAC and DC voltages from 5-150 VDC.

Q: What is the isolation voltage between outputs?

A: The isolation voltage is 250V continuous, basic insulation type, between outputs and backplane and between output-to-output.

Q: How many outputs does the 1756-OX8I have?

A: It has 8 individually isolated outputs, each with Form C contacts.

Q: What removable terminal blocks are compatible with this module?

A: Compatible RTBs are the 1756-TBCH and 1756-TBS6H.

Q: What is the expected contact life for resistive loads?

A: The expected contact life is 300 kHz for resistive loads and 100 kHz for inductive loads.

Product Support & Availability

The 1756-OX8I is available from Petro Auto Tech and is ready to ship. For current lifecycle status and ordering information, contact Petro Auto Tech directly. Please verify availability before placing an order.