An air-air heat pump and an air conditioner in heating mode operate on the same fundamental principle: they both extract heat from one location and transfer it to another. The main difference lies in their intended purposes and design considerations.
An air conditioner primarily focuses on cooling a space. It extracts heat from indoors and transfers it outside, effectively cooling the indoor environment. In cooling mode, an air conditioner utilizes a refrigeration cycle, in which a refrigerant absorbs heat from indoor air, undergoes a phase change from a low-pressure gas to a high-pressure liquid, releases heat to the outdoor environment, and then repeats the cycle.
On the other hand, an air-air heat pump can operate in both heating and cooling modes. It works similarly to an air conditioner in cooling mode, but it can reverse the refrigeration cycle to provide heating. In heating mode, the heat pump extracts heat from the outdoor air (even in cold temperatures) and transfers it indoors to warm up the space. The reversing valve in the heat pump allows it to switch between heating and cooling modes.
The distinction between an air conditioner in heating mode and an air-air heat pump is primarily in their intended use and design optimization. An air-air heat pump is specifically designed to provide efficient heating, even in colder climates, by extracting heat from the outdoor air. It is typically more powerful and has additional features to optimize heating performance. Conversely, an air conditioner in heating mode is generally less efficient in heating and may not be suitable for use in extremely cold conditions.
In summary, while the underlying principles are similar, an air-air heat pump is designed to be a powerful heating unit that can also provide cooling, while an air conditioner primarily focuses on cooling and has limited heating capability.