Allen-Bradley 1794-OW8 — 8-Point Relay Output Module | FLEX I/O Platform
Engineering Background
The Allen-Bradley 1794-OW8 is a relay output module designed for the FLEX I/O distributed I/O platform, a modular, DIN-rail-mounted system widely deployed in discrete manufacturing, process control, and machine automation environments. FLEX I/O is engineered for high-density I/O in space-constrained panels and remote I/O drops, communicating over standard Rockwell Automation networks including DeviceNet, ControlNet, and EtherNet/IP via compatible adapter modules.
Product Positioning
The 1794-OW8 provides eight isolated relay output points capable of switching both AC and DC loads, making it the preferred choice for applications requiring electrical isolation between the control system and field devices such as solenoids, contactors, pilot lights, and small motors. Its relay architecture eliminates the need for external interposing relays in many installations, reducing panel footprint and wiring complexity.
Complete Technical Specifications
- Catalog Number: 1794-OW8
- Manufacturer: Allen-Bradley / Rockwell Automation
- Platform: FLEX I/O (1794 Series)
- Module Type: Relay Output
- Number of Output Points: 8
- Output Type: Relay (Form A — SPST-NO)
- Output Voltage Range: 10–265V AC / 5–125V DC
- Maximum Output Current: 2.0 A per point (resistive load)
- Maximum Continuous Current (module): 8 A total
- Minimum Load Current: 10 mA
- Relay Isolation: Optical isolation between backplane logic and relay coil
- Electrical Isolation (field to logic): 1500V AC (tested)
- Relay Mechanical Life: ≥ 10,000,000 operations
- Relay Electrical Life: ≥ 100,000 operations at rated load
- Response Time (ON): ≤ 10 ms
- Response Time (OFF): ≤ 10 ms
- Backplane Current Draw (5V DC): 75 mA
- Operating Temperature: 0°C to +55°C (32°F to 131°F)
- Storage Temperature: -40°C to +85°C
- Relative Humidity: 5–95% non-condensing
- Dimensions (H × W × D): 94 mm × 23 mm × 87 mm
- Weight: 140 g (approx.)
- Mounting: FLEX I/O terminal base (1794-TB3, 1794-TB3S, or equivalent)
- Agency Certifications: UL Listed, CE Marked, CSA Certified, C-Tick
- ATEX / Hazardous Location: Not rated for Zone 0/1 without additional enclosure
Proven Application Environments
- Discrete Manufacturing: Conveyor control, assembly line sequencing, end-of-line testing stations
- Packaging Machinery: Solenoid valve actuation, reject gate control, label applicator triggering
- HVAC & Building Automation: Fan starter control, damper actuator switching, alarm annunciator outputs
- Water & Wastewater: Pump motor starter control, valve open/close commands, level alarm outputs
- Food & Beverage: Washdown-adjacent panel installations with isolated relay outputs for hygienic zone separation
- Oil & Gas (non-hazardous areas): Remote I/O drops for wellhead control panels and skid-mounted equipment
- Automotive: Body-in-white welding fixture control, paint booth conveyor interlocks
Engineering Advantages
- AC/DC Load Compatibility: Single module handles both AC and DC field devices without rewiring — reduces BOM complexity and spare parts inventory.
- Electrical Isolation: 1500V AC field-to-logic isolation protects the control backplane from inductive load transients and ground faults in field wiring.
- High Mechanical Life: ≥10M operations per relay ensures long service intervals in high-cycle applications.
- Compact FLEX I/O Form Factor: 23 mm wide module slots into standard 1794 terminal bases — maximizes I/O density in 35 mm DIN-rail panels.
- Hot-Swap Capable: FLEX I/O architecture supports module replacement under power (adapter-dependent) — minimizes unplanned downtime.
- Network Agnostic: Compatible with all 1794 adapter modules (DeviceNet, ControlNet, EtherNet/IP, PROFIBUS, Remote I/O) — no module change required when migrating networks.
- Rockwell Ecosystem Integration: Native Add-On Profile (AOP) support in Studio 5000 Logix Designer — plug-and-play configuration with ControlLogix, CompactLogix, and SoftLogix controllers.
System Architecture & Signal Flow
The 1794-OW8 mounts onto a 1794 terminal base, which provides both the backplane data connection and the field wiring terminals. The adapter module (e.g., 1794-AENT for EtherNet/IP) manages backplane communication and presents the module’s I/O data to the controller over the selected network. Each of the eight relay outputs is individually addressable as a discrete output bit in the controller’s I/O tree. The relay coil is driven by the backplane logic signal through an optical isolator; the relay contacts switch the field-side load circuit independently of the logic supply voltage.
Typical Wiring Topology: Field device common → Terminal base COM terminal → Relay contact (NO) → Field device load → Field power supply. Each output point has a dedicated NO contact terminal on the 1794-TB3 terminal base.
Sourcing & Quality Verification
- Source: Verified surplus and authorized distribution channels — no counterfeit risk.
- Inspection Protocol: Each unit undergoes visual inspection (label integrity, housing condition, terminal cleanliness), functional power-on test where applicable, and firmware/revision verification against Rockwell Automation published revision history.
- Packaging: Anti-static bag + foam-lined carton. Original Rockwell packaging retained where available.
- Warranty: 90-day Konmask operational warranty. Extended warranty available on request.
- Documentation: Allen-Bradley publication 1794-UM006 (FLEX I/O Relay Output Modules User Manual) available upon request.
- Revision Availability: Multiple hardware revisions in stock — specify required revision at time of order if critical.
Procurement Process
- Step 1 — Inquiry: Submit RFQ via konmask.com product page or email support@konmask.com with quantity, required revision, and delivery timeline.
- Step 2 — Quote: Receive itemized quotation within 1 business day including unit price, lead time, and shipping options (DHL Express, FedEx International Priority, sea freight for bulk orders).
- Step 3 — Order Confirmation: Purchase order or proforma invoice accepted. T/T (wire transfer), PayPal, and trade credit (approved accounts) accepted.
- Step 4 — Inspection & Dispatch: Pre-shipment inspection report provided. Tracking number issued within 24 hours of dispatch.
- Step 5 — After-Sales: Technical support available post-delivery for installation commissioning questions.
Technical FAQ
- Q: Can the 1794-OW8 switch inductive loads such as solenoid valves directly?
- A: Yes, but suppression (MOV or RC snubber) is strongly recommended across inductive loads to protect relay contacts and extend electrical life. Refer to 1794-UM006 Section 3 for suppression circuit recommendations.
- Q: Is the 1794-OW8 compatible with the 1794-AENTR (redundant EtherNet/IP adapter)?
- A: Yes. The 1794-OW8 is compatible with all 1794-series adapter modules including the 1794-AENTR. Module configuration is identical regardless of adapter type.
- Q: What terminal base is required?
- A: The 1794-OW8 requires a 1794-TB3, 1794-TB3S, 1794-TB3G, or 1794-TB3GS terminal base. The terminal base must be ordered separately if not already installed in the system.
- Q: Can outputs be grouped for common load switching?
- A: Each relay contact is independent (Form A, SPST-NO). Outputs can be wired in parallel for redundant switching of a single load, subject to current derating per the user manual.
- Q: What is the difference between 1794-OW8 and 1794-OW8I?
- A: The 1794-OW8I provides individually isolated relay contacts (each output has its own isolated common), whereas the 1794-OW8 shares a common return among all eight outputs. The OW8I is required when field devices operate at different voltages or from different power sources.
- Q: Is this module available for immediate shipment?
- A: Stock availability varies. Contact support@konmask.com or +0086 19859288691 for real-time inventory confirmation and lead time.
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