Allen-Bradley 1746-OW4 Relay Output Module

1746-OW4 SLC 500 Digital Output Module

Product Introduction

The Allen‑Bradley 1746‑OW4 belongs to the trusted SLC 500 family of programmable controller I/O modules. This digital contact output module provides four normally open (N.O.) relay contacts for switching external loads. Its operating voltage spans 5–265V AC or 5–125V DC, offering exceptional flexibility for diverse applications. Consequently, the 1746‑OW4 handles both AC and DC power circuits with ease.

This relay output module is specifically designed for applications requiring isolated dry contacts. Furthermore, it delivers reliable performance with a step response of 60 milliseconds in and 2.5 milliseconds out. Meanwhile, the module draws only 45 mA from the backplane at both 5V and 24V DC, ensuring minimal load on the system power supply. For instance, you can use the 1746‑OW4 to drive motor starters, solenoids, alarms, or pilot lights.

Key Technical Specifications

The 1746‑OW4 offers four independent relay outputs with shared common points. Each output supports a continuous current of 1.5 amps at 120V AC or 1.2 amps at 24V DC. Additionally, the minimum load current is 1 mA at 5V DC, which accommodates low-power solid-state loads. The maximum continuous current per module is 8A total across all four outputs.

Signal delay for both ON and OFF transitions is 10 ms, providing predictable switching performance. The module's thermal dissipation is remarkably low at just 1.9 W maximum, with heat dissipation per point at 0.133 W. This efficiency allows the 1746‑OW4 to operate reliably even in densely populated SLC 500 racks. The backplane current consumption remains constant at 0.045A for each voltage rail (5V and 24V DC).

Environmental and Mechanical Considerations

The 1746‑OW4 features a rugged design suitable for industrial environments. However, note that relay contact modules can be vulnerable to chemical exposure, which may degrade sealing materials over time. Therefore, periodic inspection is recommended to detect any signs of degradation. If any deterioration is found, replace the 1746‑OW4 promptly to maintain system integrity.

This module operates within standard SLC 500 temperature and humidity ranges. Its open-style enclosure allows for adequate airflow in panel installations. Meanwhile, the relay contacts are rated for millions of mechanical operations, ensuring long service life under normal switching conditions. For optimal performance, avoid installing the 1746‑OW4 in areas with corrosive gases or excessive dust.

Installation and Wiring Guidelines

Proper installation of the 1746‑OW4 begins with disconnecting power to the SLC 500 chassis. This precaution prevents accidental shock or damage during wiring. Next, slide the module into an available slot in the rack, ensuring firm seating against the backplane connector. After that, secure the module with the retaining screws.

Wire the field devices to the removable terminal block, observing correct polarity for DC loads. The 1746‑OW4 provides four N.O. relay contact outputs, each with a dedicated terminal. Always refer to the user manual for detailed wiring diagrams and torque specifications. For inductive loads, consider using external snubber circuits or surge suppressors to protect the relay contacts from arcing. Finally, restore power and verify output operation through your control program.

Packaging and Shipping

Every Allen‑Bradley 1746‑OW4 module ships in protective anti-static packaging to safeguard against electrostatic discharge. The package includes the module only; terminal blocks, mounting hardware, and cables are sold separately. We dispatch all orders using reliable global carriers: FedEx, UPS, or DHL, providing tracking numbers for full shipment visibility.

Frequently Asked Questions (FAQ)

1. Can the 1746-OW4 switch both AC and DC loads simultaneously?
Yes, each of the four relay outputs on the 1746‑OW4 can independently switch AC or DC loads, as long as the voltage stays within the specified ranges (5–265V AC or 5–125V DC).

2. What is the difference between the 1746-OW4 and a solid-state output module?
The 1746‑OW4 uses mechanical relay contacts, which provide complete isolation and handle mixed AC/DC voltages. Solid‑state modules offer faster switching but lack the voltage flexibility of the 1746‑OW4.

3. How do I protect the 1746-OW4 relay contacts from inductive load damage?
Install external surge suppressors, such as varistors or RC snubbers, across the load to limit voltage spikes. This practice extends the life of the 1746‑OW4 relay contacts.

4. What is the step response time for the 1746-OW4?
The 1746‑OW4 has a step response of 60 ms for the input side and 2.5 ms for the output side, ensuring timely actuation in control loops.

5. Can I replace the 1746-OW4 without shutting down the entire SLC 500 system?
Hot swapping is not recommended. Always power down the chassis before removing or installing the 1746‑OW4 to avoid damage and ensure operator safety.