Purchase now: Allen Bradley 1746-OX8 Isolated Relay Module
Purchase now: Atlantechdrives provides you the 1746-OX8, an advanced and highly specialized 8-channel digital relay output module designed by Allen Bradley for the SLC 500 control system. While standard relay modules (like the OW8) share electrical commons across multiple points, the 1746-OX8 is engineered for absolute electrical segregation. It features 8 individually isolated relay outputs (Normally Open). This means every single channel has its own dedicated input and output terminal, with zero shared circuitry on the field side. It is the ultimate hardware solution for complex industrial environments where you need to switch multiple completely different voltage levels, separate electrical phases, or systems with different grounding schemes all from a single PLC slot without the risk of cross-contamination or dangerous ground loops.
Technical Specifications of the 1746-OX8
The 1746-OX8 provides heavy-duty switching capabilities. Because each channel is physically separated, it offers a massive 1500V AC dielectric withstand isolation between individual output channels, as well as between the field wiring and the PLC backplane.
- Part Number: 1746-OX8
- Module Type: Individually Isolated Relay Output
- Compatible System: Allen Bradley SLC 500 (1746 Series)
- Number of Outputs: 8 Isolated Relay points (Normally Open)
- Operating Voltage (AC): 5…265V AC
- Operating Voltage (DC): 5…125V DC
- Continuous Current per Point: 2.0 Amps (Resistive)
- Isolation: 1500V AC between individual channels
- Backplane Current Draw: 85 mA at 5V DC, 90 mA at 24V DC
Expert Installation Advice: When to Use Isolated Relays
Choosing between grouped relays and isolated relays is a critical safety decision. Expert Tip: You should strictly specify the 1746-OX8 over standard relay modules when dealing with different phases of AC power or mixing safety-critical circuits. For example, if you need to switch a 120V AC Line 1 (L1) circuit on Channel 0, and a 120V AC Line 2 (L2) circuit on Channel 1, using a standard module with a shared common will cause a phase-to-phase dead short (240V explosion). Because the 1746-OX8 has individually isolated contacts, you can safely switch L1, L2, 24V DC, and an external piece of equipment’s dry contact interlock all on the very same module without any electrical interference.
Maintenance and Load Planning
Because the 1746-OX8 requires two wire connections per channel (power in, power out to load), the Removable Terminal Block (RTB) wiring is denser than a standard module. During maintenance, ensure that wires are neatly stripped and do not fray, as a stray copper strand between adjacent isolated terminals completely defeats the safety isolation of the module. Although each point can handle 2.0 Amps, ensure you still implement RC snubbers or diodes on inductive loads, as isolated relays are still susceptible to mechanical contact pitting from electrical arcing.
Frequently Asked Questions (FAQs)
Q: Can the 1746-OX8 be used as a safety relay?
A: While the isolation is robust, standard PLC modules should not be used as primary safety relays in a Category 3 or 4 emergency stop circuit. Always use dedicated, force-guided safety relays for human protection circuits.
Q: Does this module draw more backplane power than the OW8?
A: No, the backplane current draw (85mA at 5V) is practically identical to the OW8. The primary difference lies entirely in the physical separation of the copper traces on the field-wiring side of the circuit board.
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This specialized isolated relay module provides superior protection when paired with a 1746-P4 AC power supply.
