In most air-to-air heat pump systems, what is true about the indoor and outdoor coils?

The choice indicating that the indoor and outdoor coils are the same size and have the same physical capacity is often based on design considerations for most air-to-air heat pump systems. While the coils perform different functions—one absorbs heat from the indoor air and the other dissipates heat to the outdoor air—their physical dimensions can be similar to ensure balanced system performance and efficiency.

In practice, the design of heat pump systems aims to maintain efficiency across various operating conditions. Having coils of similar size can aid in achieving a balanced heat exchange, allowing the system to operate effectively under varying temperature conditions. However, the specific heat transfer capacity of each coil can differ, as they are optimized for their respective environments (indoor vs. outdoor).

It's important to note that while option C is often true in a general context, there may be exceptions in specialized systems designed for particular climates or performance needs. However, in general HVAC practice, assuming a base level of efficiency and compatibility between the coils supports the provided reasoning.

The other choices suggest different scenarios about size and function. The outdoor coil being larger or operating at different pressures introduces variables that are not uniformly applicable to all air-to-air heat pump systems. Clarifying these distinctions highlights how uniformity in coil sizing can contribute to