Why Engineers Specify the 1756-OA8E for AC Output Duty
When a ControlLogix chassis needs reliable 120V AC switching, the Allen-Bradley 1756-OA8E earns its place. This single-slot digital output module from Rockwell Automation delivers eight electronically fused AC output channels, arranged in two groups of four. Instead of relying on physical fuses that demand replacement after a fault, each channel carries its own electronic fuse — a practical advantage in continuous-process plants where downtime is measured in lost production.
The module operates across a 74-132V AC range at 47-63 Hz, with a nominal output of 120V AC. That wide band tolerates the voltage sag and swell common on industrial distribution systems, so the 1756-OA8E keeps switching even when supply conditions drift.
Key Parameters That Shape Real-World Performance
Output Current and Thermal Derating
Each point handles 2 A at 60 °C. Per group, the limit is 4 A at 30 °C or 2 A at 60 °C with linear derating. Per module, the ceiling is 8 A at 30 °C or 4 A at 60 °C, again linearly derated. Plan panel airflow accordingly — these figures assume the module sits in a properly ventilated enclosure.
Backplane and Power Budget
The module draws 200 mA at 5.1 VDC and 250 mA at 24 VDC from the backplane. Maximum power dissipation is 5.5 W at 60 °C, with thermal dissipation of 18.76 BTU/hr. Include these figures in your panel heat load calculation.
Switching Speed and Isolation
Output signal delay is 9.3 ms at 60 Hz and 11 ms at 50 Hz for both Off-to-On and On-to-Off transitions. Isolation voltage is 50 V continuous, with basic insulation type-tested at 1200V AC for 2 seconds between outputs-to-backplane and output-group-to-group.
Protection and Load Limits
Electronic fusing protects every channel. Maximum OFF-state leakage is 3 mA per point, and voltage lost in the circuit peaks at 4V in the ON state. Minimum load per point is 10 mA. Each point tolerates a 20 A surge for 43 ms, recurring every 2 seconds.
Where the 1756-OA8E Fits in Oil, Gas and Industrial Automation
Pump and valve actuation. In upstream oil and gas, AC solenoids and motor starters on pump skids often run on 120V AC. The 1756-OA8E switches these loads directly from the ControlLogix chassis, eliminating interposing relays and the wiring they require.
Packaging and material handling. Conveyor diverters, indicator stacks and AC contactors benefit from the module’s 2 A per-point rating. The wide 74-132V AC range keeps machinery running through brownout conditions that would trip narrower-tolerance output cards.
Replacement and upgrade projects. Plants migrating from older PLC platforms to ControlLogix frequently standardize on the 1756-OA8E because its electronic fusing reduces spare-fuse inventory and simplifies troubleshooting. One module covers eight points across two isolated groups, which trims panel space and wiring labor.
Installation Notes for Panel Builders
The 1756-OA8E installs in any available slot of a 1756 chassis, and there is no limit to the number of instances per chassis. It requires a 1756-TBNH or 1756-TBSH removable terminal block for field wiring — confirm you have the correct RTB on hand before commissioning. The module ships in an open-style enclosure, so it must live inside a protective panel.
Operating temperature spans 0 to 60 °C at 5-95% non-condensing relative humidity. Storage and shipping range from -40 to 85 °C. The module carries CE and UL certification and is designated T4 for temperature code purposes.
For integration into networked architectures, confirm your specific communication path and any required gateway or connection module with your supplier before ordering, since the 1756-OA8E itself is a chassis-based I/O module.
Sourcing the 1756-OA8E Without the Wait
Downtime punishes production, so availability matters as much as the specification. Oil AutoTech stocks industrial automation spares for oil, gas and process applications, with fast dispatch and worldwide delivery. If you need hands-on help confirming terminal block compatibility or matching this module to your existing ControlLogix configuration, the team can assist.
Please verify current lifecycle status and availability with Oil AutoTech before ordering.
Contact Oil AutoTech today for pricing and availability.
