Allen-Bradley 1769-OW8 | CompactLogix 8-Point AC/DC Relay Output Module — 5–265V AC / 5–125V DC / 2 Groups / DIN Rail

8 Relay Outputs for AC and DC Field Loads in CompactLogix Systems

The 1769-OW8 adds 8 normally-open relay output points to a CompactLogix controller through the 1769 expansion I/O bus. Each output contact switches AC or DC field loads within the rated voltage range — the relay's mechanical contact makes no distinction between the two. This is its primary advantage over transistor output modules: a single relay output module handles both 120V AC contactor coils and 24V DC solenoid coils on the same card without separate interface hardware.

Eight outputs are arranged in two groups of four, each group sharing a common terminal. The two commons are isolated from each other and from the bus — each group can operate at a different circuit voltage simultaneously. A group supplying 120V AC and another group supplying 24V DC can coexist on the same module, provided neither group exceeds the 2 groups × 4 points wiring arrangement.

The 10ms signal delay — both on and off — is inherent to relay mechanical operation and applies to all relay output modules regardless of manufacturer. For outputs requiring sub-millisecond switching response, transistor output modules (1769-OB series) are appropriate.

Key Specifications

Isolation Architecture — Output to Bus and Group to Group

The 1769-OW8 implements reinforced insulation between the output circuits and the CompactLogix backplane bus, and between the two output groups. The test isolation level of 1836V AC or 2596V DC (one-second test) corresponds to IEC Class 2 reinforced insulation — the same insulation class used in safety-relevant circuits where double insulation is required between field and logic sides.

This insulation level allows the 1769-OW8 to switch field loads at voltages up to 265V AC working voltage without electrical interaction with the backplane or between groups. For field installations where the output circuits must remain isolated from the PLC logic supply under all conditions, this reinforced insulation class provides the appropriate safety margin.

FAQ

Q1: What is the current rating per output on the 1769-OW8?

The output current per point depends on the connected load type and voltage. For resistive loads at 240V AC, the relay contacts typically support 2A per point. The module's heat dissipation limit of 2.83W constrains the total simultaneous switching load across all 8 outputs — calculate total power dissipation when multiple outputs switch simultaneously at high current.

Q2: Can the two output groups switch at different voltages?

Yes. The two groups of 4 outputs are isolated from each other at their common terminals. One group can switch 120V AC loads while the other switches 24V DC loads simultaneously. This is one of the practical advantages of the two-group architecture for panels with mixed-voltage field devices.

Q3: Is the 1769-OW8 compatible with CompactLogix L1, L2, and L3 controllers?

The 1769-OW8 is a 1769 Compact I/O module compatible with CompactLogix controllers that support 1769 expansion I/O. Confirm the specific controller's expansion I/O capacity and maximum module count before configuring a multi-module system.

Q4: The output is not switching even though the PLC output bit is set. What should be checked?

Verify the field supply voltage is present at the group common terminal. Confirm the connected load is within the rated voltage and current range. Use a multimeter to measure continuity across the output terminal and common when the output is forced on — a functioning relay clicks audibly and shows continuity. If no continuity with the output commanded on, the relay contact has failed.

Q5: Can the 1769-OW8 be removed and replaced with the system powered on?

Allen-Bradley recommends removing power before inserting or removing 1769 I/O modules. Doing so with power applied risks arcing at the backplane connector, which can damage the module, the adjacent modules, or the controller. Always follow the system-level power-down procedure for module replacement.