Allen-Bradley 1746-OX8 High-Current Relay Module

1746-OX8 SLC 500 High-Current Isolated Output Module

Product Introduction

The Allen‑Bradley 1746‑OX8 stands out as a premium SLC 500 digital output module with eight individually-isolated relay contact outputs. Each channel operates independently, providing superior noise immunity and eliminating common-mode interference. This design makes the 1746‑OX8 ideal for high-current switching applications where ground loops must be avoided.

Unlike grouped-output modules, this 1746‑OX8 treats each relay as a separate entity. Consequently, you can wire each output to completely different voltage sources without any shared return paths. Furthermore, the module supports both AC and DC loads across a wide voltage range from 5–265V AC or 5–125V DC. For instance, you can drive heavy inductive loads such as large motor contactors, solenoid banks, or heating elements with confidence.

High-Current Relay Performance

The 1746‑OX8 delivers exceptional current-handling capability per channel. Each output supports 3 amps continuously at 120V AC and 1.2 amps at 24V DC. Additionally, relay contact ratings include a maximum make/break of 30A at 120V AC and 15A make with 1.5A break at 240V AC. Continuous current per output is 5A for both AC voltage ratings.

For DC operation, the 1746‑OX8 provides a make/break of 0.22A at 125V DC and 1.2A at 24V DC. Continuous DC current reaches 1A at 125V and 2A at 24V. The module handles 3600 VA make and 360 VA break at AC voltages, while DC ratings deliver 28 VA for both make and break. Total module continuous current should be limited to 1440 VA for safe operation.

Signal Timing and Isolation

Signal delay for resistive loads is 10 ms for both ON and OFF transitions, ensuring consistent response in control loops. The step response measures 60 ms in and 2.5 ms out. Notably, the 1746‑OX8 features electro-optical isolation of 1500 Volts between I/O terminals and control logic, protecting the SLC 500 backplane from field-side transients.

Minimum load current is 10 mA at 5V DC, while maximum off-state leakage is 0 mA. Backplane current consumption is 0.085A at 5V DC and 0.090A at 24V DC. The module meets NEMA Standard ICS 2-230 for noise immunity, ensuring reliable operation in electrically harsh environments.

Thermal and Environmental Ratings

Heat dissipation for the 1746‑OX8 is significant due to its high-current design. Minimum dissipation is 2.590 Watts, with total dissipation reaching 8.60 Watts. Each point dissipates 0.825 Watts. Therefore, proper ventilation within the chassis is essential.

Operating temperature ranges from 0 to 60 °C ambient air surrounding the system, while storage temperature spans -40 to 85 °C. The 1746‑OX8 withstands operating vibration of 0.015 inches peak displacement at 5–57 Hz and 2.5g acceleration at 57–2000 Hz. Operating shock tolerance is 10g. Status indicators on the front panel provide real-time visual feedback for each output channel.

Installation and Wiring Guidelines

Install the 1746‑OX8 only after removing power from the SLC 500 chassis. Slide the module into any available slot—it occupies a single slot regardless of position. Secure it firmly against the backplane connector.

Each of the eight outputs on the 1746‑OX8 is fully isolated, meaning no commons are shared between channels. This feature allows independent wiring for each relay to different voltage sources or even mixed AC/DC configurations. For inductive loads, always install external surge suppression devices (e.g., RC snubbers or varistors) across the load to protect the relay contacts from arcing damage. Refer to the user manual for detailed terminal assignments and torque specifications.

Packaging and Shipping

Every Allen‑Bradley 1746‑OX8 module ships in anti-static protective packaging to prevent electrostatic discharge damage. The package includes the module only; terminal blocks and mounting hardware are sold separately. We dispatch all orders via FedEx, UPS, or DHL with tracking numbers for complete shipment visibility worldwide.

Frequently Asked Questions (FAQ)

1. What makes the 1746-OX8 different from the 1746-OW8?
The 1746‑OX8 provides eight individually-isolated outputs with 3A current capacity at 120V AC, while the 1746‑OW8 has two groups of four shared-common outputs with 1.5A per channel.

2. Can I connect different voltage sources to each output on the 1746-OX8?
Yes, because each relay on the 1746‑OX8 is fully isolated, you can wire each output to a completely separate voltage source, including mixed AC and DC supplies.

3. What is the maximum continuous current per output on the 1746-OX8?
The 1746‑OX8 provides 3A continuous per output at 120V AC and 1.2A at 24V DC. Continuous AC current rating is 5A per output.

4. Does the 1746-OX8 require external surge suppression?
For inductive loads, external surge suppression (RC snubbers or varistors) is highly recommended to protect the 1746‑OX8 relay contacts from voltage spikes and extend service life.

5. What is the isolation voltage between field and logic on the 1746-OX8?
The 1746‑OX8 provides 1500V electro-optical isolation between I/O terminals and the control logic, ensuring robust protection for the SLC 500 backplane.