Why the 1746-OW8/A Still Matters to SLC 500 Owners
Rockwell Automation ended production of the Allen-Bradley 1746-OW8/A on 2022-12-31, yet thousands of SLC 500 panels keep running packaging lines, material handling systems, and process control cabinets every day. That gap between a discontinued module and an active production line creates real business risk. Every week without a verified spare on the shelf increases the chance that a single failed relay output halts an entire machine.
This eight-channel electromechanical relay output module remains a practical workhorse because it switches both AC and DC loads through isolated normally-open contacts. For maintenance teams, the question is no longer whether to replace it, but how to manage the transition without losing production time or overspending on emergency sourcing.
What the 1746-OW8/A Actually Delivers
The 1746-OW8/A provides eight normally-open relay outputs arranged in two groups of four, giving engineers flexible control over mixed-voltage field devices. Its operating voltage range of 5-265 VAC or 5-125 VDC covers motor starters, solenoids, pilot devices, alarms, and interposing relays without external signal conditioning. Each output handles 1.5 A at 120 VAC or 1.2 A at 24 VDC, while each common carries 8 A continuous and the full module supports 16 A continuous.
Relay isolation of 1500 VAC between contacts and backplane protects the controller from field transients, a critical benefit in noisy factory environments. Signal delay sits at 10 ms ON and 10 ms OFF, which suits most discrete control tasks. The module draws 85 mA at 5V DC and 90 mA at 24V DC from the backplane, keeping power budget planning straightforward.
Key Specifications at a Glance
| Parameter | Value |
|---|---|
| Outputs | 8 normally-open relay outputs (2 groups of 4) |
| Operating voltage | 5-265 VAC or 5-125 VDC |
| Current per output | 1.5 A at 120 VAC; 1.2 A at 24 VDC |
| Current per common | 8 A continuous |
| Current per module | 16 A continuous |
| Backplane current | 85 mA @ 5V DC; 90 mA @ 24V DC |
| Signal delay | 10 ms ON / 10 ms OFF |
| Isolation | 1500 VAC contacts to backplane |
| Mounting | 1746 I/O chassis, open-style |
| Operating temperature | 0 to 60 C |
Where This Module Earns Its Keep
In a typical packaging line application, the 1746-OW8/A might drive four solenoid valves on a case sealer and four indicator lamps on an operator station, all from one module. The two-common design lets the panel builder separate AC valve circuits from DC lamp circuits without adding another card. Material handling conveyors often use the same module to energize motor starters and divert gates, where the 1500 VAC isolation keeps backplane noise away from the processor.
Process control panels benefit from the wide 5-265 VAC and 5-125 VDC range because legacy field devices rarely share a single voltage. Instead of stocking multiple output card types, a maintenance department can standardize on the 1746-OW8/A across several machines. That standardization directly reduces spare-part inventory cost and simplifies troubleshooting for technicians who move between lines.
Integration and Chassis Considerations
The module mounts in any 1746 chassis, including the 1746-A4, -A7, -A10, and -A13, which offer 4, 7, 10, and 13 slots respectively. All of these chassis are panel-mount and supply 5.1V DC at 10A plus 24V DC at 2.88A across the backplane. Slot 0 stays reserved for the processor or a 1747-ASB adapter, so planners should map slot assignments before ordering.
Field wiring lands on removable terminal blocks, and Bulletin 1492 pre-wired interface cables remain an option for faster changeouts. One safety point deserves emphasis: the 1746-OW8/A is not hot-swappable. Technicians must never install, remove, or wire the module with power applied, because doing so risks equipment damage and personal injury.
The Business Case for Stocking Spares Now
Because Rockwell has discontinued many Bulletin 1746 I/O modules and recommends migration to Compact 5000 I/O with the Logix platform, the secondary market for 1746-OW8/A units will tighten over time. Plants that delay procurement often face premium pricing or extended lead times when a failure occurs. Buying verified spares while availability is reasonable converts an unpredictable emergency expense into a planned, budget-friendly purchase.
Downtime cost usually dwarfs the price of the module itself. A single unplanned stop on a high-speed packaging or material handling line can cost far more per hour than a spare card. Keeping one or two tested 1746-OW8/A units on the shelf turns a potential multi-shift outage into a fifteen-minute swap, protecting both output and maintenance labor budgets.
Frequently Asked Questions
Is the 1746-OW8/A still in production?
No. Rockwell Automation discontinued this module on 2022-12-31, and the recommended path is migration to Compact 5000 I/O with the Logix platform. SpareTechPLC can help you locate verified remaining stock while you plan that migration.
Can I replace a failed 1746-OW8/A with a different 1746 output module?
Only if the replacement matches your field voltage and current needs. The 1746-OW8/A uniquely combines eight normally-open relay outputs, 5-265 VAC or 5-125 VDC operation, and 1500 VAC isolation, so substituting a different card may require rewiring or external relays.
What voltage can the 1746-OW8/A switch?
It handles 5-265 VAC or 5-125 VDC across its eight normally-open contacts. Each output carries 1.5 A at 120 VAC or 1.2 A at 24 VDC, with 8 A continuous per common and 16 A continuous per module.
Does the 1746-OW8/A support hot swapping?
No. The module is not hot-swappable, so you must remove power before installing, removing, or wiring it. Always follow lockout procedures and consult the official Allen-Bradley documentation for safe handling.
Securing Your SLC 500 Spares With Confidence
SpareTechPLC specializes in industrial automation spare parts and maintains deep knowledge of the SLC 500 platform, including Bulletin 1746 modules like the 1746-OW8/A. Our team verifies part numbers and condition before shipment, so buyers receive exactly what their panels need. With discontinuation pressure building across the 1746 family, acting early on spare procurement is the most cost-effective way to keep legacy lines running.
