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Key Technical Specifications
- Part Number: 1756-OA16I
- Manufacturer: Allen-Bradley / Rockwell Automation
- Product Family: ControlLogix I/O
- Module Type: AC digital isolated output
- Output Points: 16 individually isolated
- Voltage Category: 120/240 V AC, 50/60 Hz
- Operating Voltage Range: 74-265 V AC, 47-63 Hz
- Output Current: 1.0 A per point
- Isolation: 250 V continuous between outputs
- Pilot Duty: Yes
- Output Delay Time: 9.3 ms at 60 Hz
- Backplane Power: 1.59 W
Product Introduction
The Allen-Bradley 1756-OA16I is a ControlLogix AC output module used to switch 120/240 V AC loads in industrial control panels and process systems. It provides 16 individually isolated outputs with a 74-265 V AC operating range.
It fits ControlLogix chassis applications where point isolation matters. The module is commonly selected for motor starters, solenoids, pilot devices, and general-purpose AC load switching, with a 1 A per point rating and pilot duty support.
1756-OA16I
1756-OA16I
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No output voltage at one point | Field wiring open, blown load fuse, or upstream supply issue | ⚠️ Medium | Measure AC voltage at the terminal block and check the load side with a meter | Check wiring and load circuit before replacing the module |
| Multiple outputs fail together | Chassis power issue or common field power problem | ❌ Low | Verify chassis backplane status and measure field supply feeding the loads | Inspect power distribution first |
| Output stays off even when commanded ON | Program logic, interlock, or safety circuit blocking the command | ❌ Low | Check controller tag status and output command bits in the PLC software | Confirm logic and permissives before blaming the module |
| Output is stuck ON | External short, welded relay/contactor, or wiring fault | ⚠️ Medium | Remove field wiring and re-test the point with a known-good load | Replace the module only after isolating the field circuit |
| Erratic switching or chatter | Load voltage instability or marginal field wiring | ⚠️ Medium | Measure line voltage under load and inspect terminal torque | Stabilize the field supply and retest |
| Module not recognized by controller | Wrong chassis slot, poor seating, or backplane issue | ⚠️ Medium | Reseat the module and inspect the chassis connector | Check chassis/backplane before ordering a replacement |
| Output LED on, but load does not actuate | Load requires more current than the module or field supply can deliver | ⚠️ Medium | Measure current draw and verify load rating against the nameplate | Reduce load or add an interposing device |
If you are stuck, send technical support clear photos of the module, terminal wiring, and controller diagnostics logs.
Frequently Asked Questions
Q: Is the 1756-OA16I a direct replacement for all ControlLogix AC output cards?
A: No. It is specific to ControlLogix chassis applications and AC output use. Verify the exact catalog number, terminal block, voltage range, and load current before swapping it in.
Q: Can I hot-swap the 1756-OA16I?
A: In many ControlLogix systems, modules can be removed and inserted under the proper procedure, but do not assume the field wiring is safe. Kill the field power if there is any doubt, because a live AC load can arc or damage the terminals.
Q: Does this module keep its configuration after a swap?
A: The module itself does not store your whole application. Your controller program and module configuration live in the ControlLogix project, so you should still verify slot assignment and I/O mapping after replacement.
Q: Why is this priced lower than a factory-new unit?
A: New Surplus or New Original stock is usually priced lower because it is unused inventory from overstock, project closeout, or excess procurement. That is normal, but you should still confirm condition, test status, and warranty terms before buying.
Q: What should I check before installing a replacement?
A: Match the catalog number, confirm the terminal block style, verify field voltage, and check the load current per point. I also recommend taking a photo of the old wiring and slot layout before removal.
Q: What kind of loads can it switch?
A: It is intended for AC loads in the 74-265 V AC range, such as pilot devices, solenoids, and control relays. For inductive loads, check inrush current and make sure you stay inside the module and field device limits.
Q: Is there any firmware risk with this part?
A: The module is mainly an I/O device, so the bigger risk is usually compatibility with the chassis, controller, or project configuration rather than a firmware mismatch. Still, verify the exact revision if your site standard is strict.
