NATE Air Conditioning and Heat Pumps Practice Exam 2026 – All-in-One Guide to Master Your Certification!

The correct answer is related to the requirement for power supply to specific components of the thermostat. Electromechanical thermostats often incorporate display lights on their subbase, which provide visual feedback regarding the thermostat's status and settings. These display lights need a continuous source of power to function correctly, and connecting to both sides of the transformer ensures that they receive the necessary voltage and current to illuminate reliably.

While components like cooling or heat anticipators are important for the regulation of system performance, they typically do not necessitate such a direct and continuous power connection from both sides of the transformer in the same way that display lights do. A microprocessor, on the other hand, would generally be found in more advanced digital thermostats, which may not fall under the category of electromechanical devices. Thus, focusing on the lighting functionality elucidates why this answer is appropriate given the context of electromechanical thermostat operation.