Introduction to the 1746-OX8 Relay Output Module
When your SLC 500 system needs to switch high-current loads with complete electrical isolation, the Allen-Bradley 1746-OX8 delivers. This digital contact output module packs eight normally-open relay contacts into a single slot, giving you the flexibility to control motors, solenoids, and indicator lamps directly from your PLC. As a trusted supplier of industrial automation parts, SpareTechPLC offers this module for engineers who refuse to compromise on reliability.
Why the 1746-OX8 Belongs in Your Control Cabinet
The 1746-OX8 solves a common problem: driving multiple high-current devices without adding external interposing relays. Each of the eight outputs is individually isolated, which means a fault on one channel won’t cascade to the others. This isolation also protects your backplane and control logic from voltage spikes and noise. With an operating voltage range of 5-265 Volt AC or 5-125 Volts DC, the module adapts to a wide variety of industrial power environments.
Technical Specifications That Matter
The 1746-OX8 operates on a backplane current of just 85-90 milliamps, making it an efficient choice for dense I/O configurations. Each output handles up to 3 amps at 120 VAC or 1.2 amps at 24 VDC. The relay contacts are normally open, so they remain de-energized until your program commands them to close. This fail-safe design is ideal for applications where an unintended activation could be dangerous.
For engineers upgrading legacy SLC 500 systems, the 1746-OX8 is a direct-fit replacement that requires no adapter. It mounts in any standard 1746 chassis and communicates seamlessly with your existing processor. The module’s step response is 60 milliseconds in and 2.5 milliseconds out, providing predictable timing for sequencing operations.
Where the 1746-OX8 Excels
Manufacturing and Assembly Lines
In automotive assembly, the 1746-OX8 controls pneumatic clamps, conveyor diverters, and safety gates. The individually isolated contacts prevent cross-talk between high-power devices, ensuring that a jam on one station doesn’t disrupt the entire line.
Water and Wastewater Treatment
Pump control panels rely on robust relay outputs. The 1746-OX8’s ability to switch 5-265 Volt AC means it can directly drive motor starters and valve actuators without additional relays. Its operating shock rating of 10 g ensures it survives the vibrations common in pump rooms.
Building Automation and HVAC
The module’s wide voltage range accommodates both 24 VDC control circuits and 120 VAC damper actuators. Facility managers appreciate the reduced panel space and wiring complexity that comes with eight isolated outputs in one slot.
Installation and Setup Best Practices
Always remove power from the chassis before installing or removing the 1746-OX8. The module has an open-type enclosure, so it must be mounted inside a protective cabinet. Verify that your backplane can supply the required 85-90 milliamps. Use ferrules on all field wiring to prevent stray strands from bridging adjacent terminals. Since the outputs are normally open, plan your wiring so that the safe state corresponds to a de-energized relay.
Maintenance and Reliability
Relay contacts are mechanical components, so periodic inspection is essential. Check for pitting or carbon buildup on the contact surfaces every 12 months or after 100,000 operations, whichever comes first. The 1746-OX8 operates in ambient temperatures from 0 to 60 degrees Celsius. Keep the cabinet filter clean to prevent dust from accelerating contact wear. If you notice erratic switching, verify that the load current does not exceed 3 amps at 120 VAC or 1.2 amps at 24 VDC.
Compatibility and Integration
The 1746-OX8 is designed for the SLC 500 platform and works with any 1746 chassis and processor. It requires no special firmware or configuration software. Because it uses relay contacts rather than solid-state outputs, it can interface with AC and DC loads on the same module, giving you unmatched flexibility in mixed-voltage panels.
Selection Guide: What to Verify Before You Buy
Before ordering the 1746-OX8, confirm your chassis has an open slot and that your power supply can handle the additional 85-90 milliamps of backplane current. Check that your load currents fall within the 3 A at 120 VAC or 1.2 A at 24 VDC limits. If you need normally closed contacts or a different channel count, explore other SLC 500 modules. SpareTechPLC stocks the 1746-OX8 and can help you verify compatibility with your existing system.
Frequently Asked Questions
Can the 1746-OX8 switch both AC and DC loads on the same module?
Yes. Each output is individually isolated, so you can mix AC and DC voltages across the eight channels without interference.
What is the maximum current per output at 120 VAC?
The 1746-OX8 handles up to 3 amps per output at 120 VAC.
Does the 1746-OX8 require any special configuration?
No. The module is plug-and-play within any SLC 500 chassis. Your processor recognizes it automatically.
What is the operating temperature range for the 1746-OX8?
The module operates in ambient temperatures from 0 to 60 degrees Celsius.
How often should I inspect the relay contacts?
Inspect contacts every 12 months or after 100,000 operations. Replace the module if you see significant pitting.
