In HVAC practice, which type of heat exchange system uses the earth as a heat source or sink?

• A. Geothermal heat pump
• B. Air conditioner
• C. Furnace
• D. Chiller

Answer: (A)

Using the earth as a heat source or sink is what geothermal (ground‑source) heat pump systems do. They circulate a fluid through buried loops, exchanging heat with the ground. In heating mode, the ground’s relatively constant underground temperature provides heat that the heat pump collects and distributes into the building. In cooling mode, the system transfers heat from the building to the cooler ground, using the earth as the heat sink. This setup offers steady performance and high efficiency because the ground doesn’t heat up or cool down as much as outdoor air does.

Other options don’t use the earth for heat exchange: an air conditioner exchanges heat with outdoor air, a furnace relies on combustion to generate heat, and a chiller cools water through a refrigerant cycle without using the earth as a heat source or sink.