Allen-Bradley 1790-0W8X 8-Relay Output Module

Allen-Bradley 1790-0W8X 8-Relay Output Expansion Module

Product Introduction

The 1790-0W8X module belongs to the CompactBlock LDX series. It offers 8 relay outputs for distributed I/O systems. Unlike solid-state modules, this relay type handles both AC and DC loads. Each channel uses a Form A (normally open) single-pole single-throw contact. You can switch resistive loads up to 2.0A at 24V dc or 30V ac. Therefore, the 1790-0W8X suits applications requiring voltage mixing or isolation.

Technical Specifications

Relay Output Characteristics

The 1790-0W8X delivers 8 normally open relay outputs. The output voltage range depends on your load. For DC, it handles 5V dc to 24V dc at 2.0A resistive. For AC, it handles up to 30V ac at 2.0A resistive. Each channel supports a maximum output current of 2.0A at rated power. The minimum load requirement is 100 µA at 100 mV dc.

Additionally, the on-state voltage drop reaches 0.5V max at 2.0A with a 24V dc resistive load. Initial contact resistance is only 30 mΩ. The off-state leakage current stays below 1.5 mA max. Output delay time measures 10 ms max for both off-to-on and on-to-off transitions. Eight green status indicators show the relay states clearly.

Contact Life and Reliability

Expected contact life reaches 300 Kcycles for resistive loads. For inductive loads, the life spans 100 Kcycles. This difference matters when switching motors or solenoids. We recommend adding arc suppression for inductive loads. Doing so extends the relay life significantly.

Common Type and Wiring

The 1790-0W8X uses a 1 point per 1 COM configuration. Each output has its own isolated common terminal. This arrangement allows you to mix voltages freely. For example, channel 1 can switch 24V dc while channel 2 switches 120V ac. No internal connections exist between commons.

General Electrical Data

Field power supply voltage nominally sits at 24V dc. Its operating range extends from 19.2V dc to 28.8V dc. Power dissipation reaches 10 mA at 28.8V dc per channel. For all 8 channels active, expect around 80 mA total. Isolation between I/O and logic uses photocoupler technology. The isolation voltage is rated at 1250V ac rms. For wiring, the module employs a 37-pin D-shell connector.

Mechanical and Environmental Parameters

The 1790-0W8X carries an IP20 protection rating. It is designed for use inside control cabinets. Operating temperature typically ranges from 0°C to 55°C. Storage temperature spans -25°C to 85°C. Relative humidity should stay between 5% and 95% non-condensing. Vibration resistance meets IEC 60068-2-6 standards. Shock resistance complies with IEC 60068-2-27.

Installation Guide

First, disconnect all power before wiring the 1790-0W8X. Next, mount the expansion block onto a DIN rail or panel. Then, connect the 37-pin D-shell cable to the module. After that, wire the 24V dc field power to the designated terminals. For each output channel, connect your load between the output and its dedicated common.

Furthermore, verify each relay load stays under 2.0A. For inductive loads like relays or solenoids, install a flyback diode (DC) or RC snubber (AC). This practice prevents contact welding and extends relay life. Use copper conductors with a wire gauge of 0.5 to 1.5 mm². Tighten all screws to the torque specified in the manual. Once wiring completes, apply power and observe the green status LEDs.

Packaging List

• 1790-0W8X module (1 unit)

• 37-pin D-shell connector (1 piece, pre-attached)

• Installation instructions sheet

• DIN rail mounting clips (2 pieces)

Note: No certificates or warranty documents are included.

Shipping

We ship all orders via FedEx, UPS, or DHL. Delivery typically takes 3-7 business days worldwide.

Frequently Asked Questions (FAQ)

1. Can the 1790-0W8X switch 220V AC loads?
No. The maximum AC voltage rating is 30V ac. For higher AC voltages, consider other relay modules from Allen-Bradley.

2. What is the difference between 1790-0W8X and solid-state output modules?
The 1790-0W8X uses mechanical relays with isolated commons per channel. It handles both AC and DC loads. Solid-state modules like the 1790-0B16X switch DC only but offer faster speeds.

3. How do I protect the relay contacts on my 1790-0W8X?
For DC inductive loads, add a flyback diode across the load. For AC inductive loads, add an RC snubber across the relay contacts. These steps prevent arcing and extend contact life.

4. Why do my relay outputs click but the load does not turn on?
First check the field power supply (19.2-28.8V dc). Then verify the load wiring and common connections. Each channel has an independent common, so both output and its paired common must connect.

5. Can I replace a failed relay on the 1790-0W8X?
No. The relays are soldered onto the circuit board. You must replace the entire 1790-0W8X module if a relay fails.