When you set your air conditioner (AC) to "heat," it doesn't function as a traditional cooling AC unit. Instead, most modern AC systems, particularly central heating, ventilation, and air conditioning (HVAC) systems, are designed as heat pumps. A heat pump can work in both heating and cooling modes by transferring heat from one place to another.
Here's how the heat pump functions when you set it to "heat":
Reversing Valve: Heat pumps have a component called a reversing valve. This valve allows the heat pump to switch between heating and cooling modes. When you set the thermostat to "heat," the reversing valve changes the flow of refrigerant in the system.
Absorbing Heat: In heating mode, the heat pump absorbs heat from the outside air, even in cold weather. The refrigerant in the system absorbs this heat energy and becomes a warm gas.
Compressor: The warm gas is then compressed by the compressor in the heat pump. Compression increases the temperature of the gas even further.
Condenser Coil: The hot gas passes through a condenser coil inside your home. As the hot refrigerant circulates through the coil, it releases heat to the indoor air, warming up your home.
Blower and Ducts: The blower in the heat pump's indoor unit then circulates the heated air through the ductwork of your home, distributing it to different rooms.
Cooling Mode: When you set the thermostat to "cool," the reversing valve changes the flow of refrigerant once again, and the process is reversed. The heat pump now acts as a traditional air conditioner, absorbing heat from inside your home and releasing it outside.
It's important to note that heat pumps work most efficiently in moderate climates. In extremely cold climates, the heat pump may struggle to extract enough heat from the outside air, and supplementary heating, such as electric resistance heating or a backup furnace, may be required to provide adequate warmth.
By having this dual-functionality, heat pumps offer a convenient and energy-efficient way to maintain comfortable indoor temperatures both during hot summers and chilly winters.