1791-8AR Block I/O Module – Oiltech Controls Insight
This 1791-8AR combines 8 AC inputs and 8 relay outputs in a compact Remote I/O node. It includes an embedded power supply and RIO interface for distributed control.
Core Technical Data
- Brand: Allen-Bradley | Series: 1791 Block I/O
- Inputs: 8 x 120V AC (ON: 79-132V AC, 12.3mA max)
- Outputs: 8 x Relay (125V DC @ 1A / 20-30V DC @ 1A / 125V DC @ 0.2A)
- External Power: 85-132V AC, 150 mA
- Power Dissipation: 12.9 W max; Thermal: 56.1 BTU/hr
- Mounting: Vertical or horizontal
- Weight: 1.00 lbs (0.45 kg)
Remote I/O (RIO) Compatibility
- Supports PLC-2, PLC-3, PLC-5, and SLC 500 with 1747-SN scanner
- Baud rates: 57.6K, 115.2K, 230.4K (cable length up to 10,000 ft)
- Daisy-chain topology with terminating resistors (82 Ω or 150 Ω)
Typical Loads & Applications
- Input devices: Limit switches, proximity sensors, pushbuttons, relay contacts
- Output loads: Pilot lamps, relay coils, solenoid valves, annunciators
- Ideal for legacy RIO upgrades and distributed I/O retrofits
5 Professional FAQs (with experience-based answers)
Q1: Can this module work with a modern ControlLogix system?
Not natively. You need a 1756-DHRIO or 1756-RIO module to bridge RIO to ControlLogix. Many users use this as a cost-effective remote I/O for legacy plants.
Q2: What is the maximum cable length for reliable communication?
At 57.6K baud, 10,000 ft; at 115.2K, 5,000 ft; at 230.4K, 2,500 ft. Always use Belden 9463 or equivalent cable and proper terminating resistors.
Q3: Can I mix AC and DC loads on the relay outputs?
Yes, each relay is isolated. However, for DC inductive loads, install a freewheeling diode to extend contact life. We recommend external suppression.
Q4: Is this module suitable for high-vibration environments?
Yes, but mount it horizontally to reduce stress on terminal blocks. Use shielded cable for input wiring if noise is a concern.
Q5: What if I need more than 8 inputs?
You can daisy-chain multiple 1791 blocks on the same RIO trunk. Each block uses a unique node address (dip switch set).
Shipping & Warranty
- Dispatch: 24–28 hours after order confirmation
- Carriers: FedEx, UPS, DHL (tracking provided)
- Warranty: 12 months against manufacturing defects
Why Buy From Oiltech Controls?
- Over 15 years specializing in industrial automation spares
- Global shipping with real-time tracking
- Tested surplus / refurbished units with full functionality check
- 12-month warranty on every module
- Technical verification performed before shipment
- Expert support for obsolete and legacy control systems
Contact: info@oiltechcontrols.com | +86 158 8020 0923
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