When a stepper motor expansion device receives a signal from the controller, what is its response?

The response of a stepper motor expansion device to a signal from the controller is to rotate a precise, small amount. This is fundamental to its design and function. Stepper motors are designed to move in defined increments, or "steps," allowing for very controlled and accurate adjustments. In HVAC/R applications, this precise movement enables the expansion device to modulate the flow of refrigerant effectively, ensuring optimal cooling performance and efficiency.

The ability to rotate in small, exact increments means that the device can make real-time adjustments based on system demands, contributing to better temperature control and system responsiveness. This level of precision is crucial in balancing the system, enhancing efficiency, and preventing issues like flooding or starvation of the evaporator.

In contrast, while other options may represent different behaviors or components in an HVAC system, they do not accurately depict the function of a stepper motor expansion device. The focus on precise control is what distinguishes it, making this choice the right response to the question.