Which of the following is NOT a typical application for a PLR?

• A. HVAC functions
• B. Small residential circuits
• C. Room lighting control
• D. Large, complex industrial processes

Answer: (D)

PLR devices are meant for simple, localized control tasks with a limited number of inputs and outputs and basic programming capabilities. They’re compact, cost-effective solutions for straightforward automation needs, so they fit well in settings like HVAC control, small residential circuits, and room lighting control where you don’t need a lot of I/O or advanced features.

Because of that limited I/O, memory, and processing power, a PLR isn’t well-suited to handle large, complex industrial processes that require extensive input/output, robust programming, networking, redundancy, and advanced diagnostics. Those demanding environments typically rely on more capable controllers like PLCs or DCS systems.

So, the choice describing large, complex industrial processes isn’t a typical PLR application.