Purchase now: Allen-Bradley 1756-OW16I ControlLogix Isolated Relay Module
Atlantechdrives provides you the 1756-OW16I, a high-density 16-point N.O. (Normally Open) relay output module. This «I» version stands for individual isolation, providing 16 completely independent relay contacts. This module is the ideal choice for applications that require mixing AC and DC voltages or different power phases on a single module while maintaining total electrical separation.
- Outputs: 16 Normally Open (N.O.) Relays
- Isolation: 100% Point-to-Point Isolation
- Voltage Range: 5-125V DC / 10-265V AC
- Current Rating: 2A per point (limited by total module current)
- Response Time: 10ms (max) for both ON and OFF
Technical Performance: The Versatility of Relay Isolation
The 1756-OW16I is engineered for maximum flexibility in the ControlLogix chassis. Unlike standard relay modules that use common returns for groups of points, the 1756-OW16I provides 16 pairs of contacts that are electrically isolated from each other and the backplane. This allows you to control a 24V DC solenoid on Point 0, a 120V AC motor starter on Point 1, and a 230V AC indicator lamp on Point 2—all within the same module. This individual isolation is critical for preventing cross-phase short circuits and for meeting strict safety standards in power distribution and material handling systems where varied voltage levels are a requirement.
Installation Advice: Protecting Relay Contacts
To ensure the longevity of the 1756-OW16I, protecting the mechanical relay contacts is mandatory. When switching inductive loads (such as solenoids, contactors, or small motors), the resulting back-EMF can cause arcing across the contacts, leading to premature failure or «welding» of the relay. We highly recommend installing RC snubbers for AC loads and flyback diodes for DC loads directly at the field device. For wiring, use the 36-pin 1756-TBCH terminal block. Given that each point has two wires, ensure your wire markers are clear and that you use a wire gauge (18-22 AWG) that allows for easy routing within the terminal block cover.
Maintenance and Lifecycle Management
Mechanical relays have a finite lifespan based on the number of switching cycles and the load current. The 1756-OW16I is a «long-life» module, but we recommend monitoring the cycle counts in your PLC logic for high-frequency outputs. If a point is switching more than once every few seconds, consider replacing that specific device with a solid-state module (like the 1756-OB16E). Periodically check the «Module Info» tab in Studio 5000 for any communication faults. The individual LEDs on the front panel will show you exactly which relays are energized, making it easy to troubleshoot field-side power issues without opening the terminal block.
FAQs
Q: What is the maximum current per point for the 1756-OW16I?
A: It can handle 2.0A per point, but you must respect the total module current limit (typically 16A per module @ 60°C).
Q: Can I mix AC and DC on the same 1756-OW16I?
A: Yes, because every point is individually isolated, you can mix different voltages and types on any channel.
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This isolated relay output module is essential for universal load switching and requires a robust 1756-PA75 AC power supply.
