How does a heat pump operate in heating mode versus cooling mode, and what is the role of a reversing valve?

• A. In cooling mode refrigerant absorbs indoor heat; in heating mode the reversing valve changes flow so outdoor air provides heat; the reversing valve switches between modes.
• B. In heating mode refrigerant absorbs outdoor heat; in cooling mode it releases heat outdoors; no valve movement.
• C. Heat pumps only provide cooling; reversing valve has no effect in heating.
• D. The reversing valve increases system pressure regardless of mode.

Answer: (A)

The main concept here is that a heat pump moves heat rather than generating it, and a reversing valve is what lets it switch the direction of heat transfer. In cooling mode, the indoor air is cooled because the refrigerant absorbs heat from inside the space and rejects it outdoors. In heating mode, the flow is reversed so the outdoor air becomes the heat source and the indoor space receives heat, with the outdoor coil acting as the evaporator and the indoor coil as the condenser. The reversing valve physically redirects the refrigerant flow to switch between these two configurations. This explains why cooling mode involves taking heat from inside, heating mode draws heat from outside, and why the valve’s action is essential to changing modes.