Purchase now: Allen-Bradley 1756-IM16I Isolated Input Module
Purchase now: Atlantechdrives provides you the 1756-IM16I, a heavy-duty, industrial-grade 16-point 220V/240V AC digital input module flawlessly engineered by Rockwell Automation for the elite ControlLogix 1756 programmable automation controller (PAC) system. While modern machine control generally utilizes 24V DC, legacy heavy industries—such as primary steel smelting, massive port crane operations, and legacy power generation facilities—frequently rely on 220V to 240V AC control circuits to overcome massive voltage drops across sprawling physical distances. The 1756-IM16I is the ultimate bridge for these high-voltage signals. Crucially, the «I» designation signifies that this module is Individually Isolated. Each of its 16 input channels possesses dedicated internal galvanic isolation and its own separate electrical return (common) terminal. This sophisticated architecture allows control engineers to safely land 240V AC signals sourced from entirely different electrical grids, disparate transformers, or opposing motor phases directly into a single ControlLogix chassis without the catastrophic risk of phase-to-phase short circuits or highly destructive ground loops.
Technical Specifications of the 1756-IM16I
The 1756-IM16I delivers an incredibly robust physical barrier between the extreme high-voltage factory floor and the highly sensitive 5V DC silicon logic of the PLC backplane, guaranteeing maximum CPU protection against lightning strikes and severe electrical surges.
- Part Number: 1756-IM16I
- Platform: ControlLogix 1756 System
- Input Type: Digital AC Input (Individually Isolated)
- Number of Inputs: 16 Points (16 separate commons)
- Operating Voltage Range: 159…265V AC, 47…63 Hz
- Nominal Input Voltage: 220V / 240V AC
- Maximum Input Current: 13 mA at 265V AC per channel
- Required Terminal Block (RTB): 1756-TBCH (36-pin cage clamp) or 1756-TBS6H
- Backplane Current Draw: 100 mA at 5.1V DC; 3 mA at 24V DC
Expert Tips: The Danger of Shared Commons at 240V AC
Specifying an isolated module for 240V AC applications is often a matter of critical plant safety. Expert Tip: If you attempt to wire multiple 240V AC signals from different phases (e.g., L1 and L2) into a standard, non-isolated module that shares a single common terminal, you will instantly bridge those phases together. This creates a violent 400V+ AC phase-to-phase dead short that will obliterate the input module and potentially cause a severe electrical fire inside the control panel. The 1756-IM16I provides 16 electrically independent circuits, meaning you can safely land an L1 signal on Channel 0 and an L2 signal on Channel 1 without any cross-conduction, giving you ultimate architectural freedom when retrofitting older machinery.
Installation Advice: Managing High-Voltage Wire Routing
Because every channel is individually isolated, the 1756-IM16I requires two physical wires for every single input (the hot signal and its dedicated neutral). A fully populated module will force 32 physical high-voltage wires into the 36-pin Removable Terminal Block (RTB). You must exercise extreme caution during installation. 240V AC can be lethal. Ensure that all wire insulation is properly stripped—not too short, and not too long—and that high-quality insulated wire ferrules are used. A single stray copper strand jumping between adjacent terminals at 240V AC will cause an immediate arc flash. Furthermore, these 240V AC wires must be strictly segregated from your low-voltage Ethernet and analog cables inside the panel’s wire ducting to prevent induced electromagnetic noise.
Frequently Asked Questions (FAQs)
Q: What is the off-state leakage current limit for this module?
A: The 1756-IM16I has a maximum off-state leakage current specification of 2.5 mA. If your field device (like an older AC proximity switch) leaks more than this when «OFF», the module will register a false «ON» signal. You must install a bypass resistor in the field to drain this excess current.
Q: Can I hot-swap the 1756-IM16I while the PLC is running?
A: Yes, it supports Removal and Insertion Under Power (RIUP). However, because you are dealing with 240V AC, you must physically unclip and remove the front wired RTB to disconnect the lethal field power before pulling the actual electronic module out of the chassis.
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here.
This high-voltage isolated AC input module fits perfectly into a standard 1756-A10 10-slot chassis for system expansion.
