Introduction to the Allen-Bradley 1746-OX8
Is your SLC 500 system struggling to drive high-current loads? The Allen-Bradley 1746-OX8 digital contact output module solves this by providing eight individually isolated, normally open relay contacts. This module is designed for applications that demand robust switching of AC or DC loads, ensuring your control system operates reliably even under heavy demands.
Key Technical Specifications
The 1746-OX8 operates with a wide voltage range: 5-265 Volt AC or 5-125 Volts DC, making it versatile for various industrial environments. Each output can handle 3 amps at 120 VAC or 1.2 amps at 24 VDC, sufficient for many high-current relay applications. The module draws 85-90 milliamps from the backplane, ensuring compatibility with standard SLC 500 power supplies. With a step response of 60 milliseconds in and 2.5 milliseconds out, it provides responsive control for your processes.
Output Ratings and Isolation
Each of the eight outputs is individually isolated, which prevents cross-talk and allows mixing of different voltage types. The relay contacts are rated for high inrush currents, with a maximum make of 30 A and break of 15 A at 120 VAC. This makes the module ideal for controlling motors, solenoids, and other inductive loads. The electro-optical isolation of 1500 Volts between I/O terminals and control logic ensures safety and signal integrity.
Applications and Use Cases
In manufacturing, the 1746-OX8 can control high-power relays that switch conveyor motors or heating elements. For example, in a packaging line, it can manage the start/stop of a 3-phase motor through a contactor, thanks to its 3 A rating at 120 VAC. In water treatment plants, it can operate solenoid valves for flow control, leveraging its isolated outputs to prevent ground loops. The module’s ability to handle both AC and DC loads makes it a go-to choice for retrofit projects where legacy equipment needs reliable switching.
Installation and Setup
Installing the 1746-OX8 is straightforward: it mounts in any SLC 500 chassis with an open-type enclosure. Always ensure power is removed from the chassis before inserting or removing the module to avoid damage. Wiring involves connecting field devices to the output terminals, which are clearly marked. Since the outputs are normally open, you must provide external power for the loads. Follow local electrical codes and use appropriate wire gauges for the current ratings.
Maintenance and Reliability
To ensure long-term reliability, inspect the module periodically for loose connections or signs of overheating. The relay contacts have a finite lifespan, so monitor for increased resistance or welding. Operating temperature should remain between 0 and 60 degrees Celsius; ensure adequate ventilation in the enclosure. The module’s shock and vibration ratings (10 g shock, 2.5 g vibration) make it suitable for harsh environments, but avoid excessive mechanical stress.
Compatibility and Integration
The 1746-OX8 is part of the SLC 500 series and works seamlessly with other SLC 500 modules and processors. It communicates via the backplane, so no special configuration is needed beyond addressing. For systems using remote I/O, it can be integrated with scanners. This module is a direct replacement for older relay output modules, offering improved isolation and current handling.
Selection Guide
Before purchasing, verify your system’s voltage requirements and load currents. The 1746-OX8 is ideal for high-current, isolated applications. Ensure your chassis has available slots and sufficient backplane power. For assistance, contact SpareTechPLC, a trusted supplier of industrial automation parts. They can help you confirm compatibility and availability.
Frequently Asked Questions
What is the maximum current per output on the 1746-OX8?
Each output can handle up to 3 amps at 120 VAC or 1.2 amps at 24 VDC. For other voltages, refer to the derating curve in the manual.
Can I use the 1746-OX8 with DC loads?
Yes, it supports DC voltages from 5 to 125 Volts, with a maximum current of 1.2 amps at 24 VDC.
Is the 1746-OX8 compatible with all SLC 500 processors?
Yes, it works with any SLC 500 processor that supports digital output modules. Just ensure the backplane power budget is not exceeded.
How do I troubleshoot a faulty output?
Check for proper wiring and load conditions. If an output fails to switch, test the relay contact with a multimeter. Replace the module if contacts are welded or show high resistance.
