How Does A Heat Pump Work In Winter?

Heat pumps cool indoor air in summer, but how does a heat pump work in winter? Interestingly, heat pumps operate the same way whether cooling or heating. The refrigerant’s direction determines whether heat is removed from or supplied to a building. Heat pumps are two-for-one systems that can replace air conditioner and furnace combos.

Although heat pumps are not often recognized as home heating systems, they are superior to other electric heaters in efficiency. Heat pump systems use roughly fifty percent less energy than electric furnaces and baseboard heaters, yielding lower utility bills. Dual climate-control abilities and energy efficiency make heat pump installation worth considering.

A heat pump is a highly efficient heating and cooling system that transfers heat between a building and the outdoor air, ground, or water. Heat pumps are essentially two-way air conditioners. Though heat pumps are predominantly electric, gas absorption heat pumps run on alternative energy sources.

Many styles of heat pumps are available today. Heat pump systems come in different sizes, configurations, and price points. They can be components of forced-air systems and deliver treated air through ductwork or be packaged in single units that directly distribute air. Some heat pump systems have extensive installation requirements and others have minimal demands. However, every heat pump system transfers heat between indoor and outdoor spaces with refrigerants. Heat transference allows all heat pumps to be incredibly energy efficient. The most common types of heat pumps are classified by the source with which they transfer heat–air, ground, and water.

Heat pumps operate like reverse air conditioners in winter, absorbing heat from the outdoor air and transferring it indoors. The reversing valve reverses the refrigerant’s flow: the indoor evaporator becomes the condenser and vice versa. Thermal energy is always available in the outdoor air, even in cold temperatures.

Although heat pumps work in winter, they often include auxiliary heat backup systems. Electric heat strips in the air handler are commonplace, but some houses use boilers and furnaces. A dual-fuel heat pump combines a heat pump with a gas furnace, which is a good option for cold climates. Heat pump heat is milder than furnace heat but shouldn't be cold. A heat pump blowing cold air in winter typically signifies an issue.

The outside air is the heat source in heating mode, and the heat energy transfers inside—the outdoor coil functions as an evaporator, and the indoor coil functions as a condenser.

1. Cold, liquid refrigerant in the outdoor unit’s coil absorbs heat from the outside air. The refrigerant evaporates into a gas as it heats up.

2. The compressor pressurizes the refrigerant, increases its temperature, and sends it to the indoor coil.

3. The refrigerant flows through the indoor coil. Cold household air blows over the coil and the refrigerant’s heat transfers to the atmosphere. A fan blows the heated air into the home. The refrigerant cools and condenses into a liquid.

4. The refrigerant returns to the outdoor unit and the expansion valve reduces pressure and decreases temperature. The refrigerant returns to a cold, liquid state and repeats the cycle.

The heat pump defrost cycle removes frost accumulating on the outdoor coil during winter weather. Ice accumulations form on the coil amid cold temperatures and high humidity levels, decreasing heat absorption and system efficiency. When frosty conditions occur, the defrost cycle automatically activates. The heat pump reverses the refrigerant’s flow and directs the hot refrigerant to the outdoor coil. During the process, the indoor coil absorbs the home’s heat in cooling mode, and cool air blows from the system. The defrost cycle typically ends when the outdoor coil reaches 58°F and lasts five to fifteen minutes. The cycle repeats every thirty to ninety minutes.

The house’s air is the heat source in cooling mode, and the heat energy transfers outside—the indoor coil functions as an evaporator, and the outside coil functions as a condenser.

1. Cold, liquid refrigerant in the indoor coil absorbs heat from the home’s air. The refrigerant evaporates into a gas as it heats up.

2. The refrigerant flows to the outdoor unit. The compressor pressurizes the refrigerant, increases its temperature, and pumps it through the outdoor coil.

3. The refrigerant flows through the coil while a fan supplies air, and heat releases into the outdoor air. The refrigerant cools and condenses into a liquid.

4. The expansion valve reduces the refrigerant’s pressure and decreases its temperature. The refrigerant returns to the indoor coil in a cold, liquid state and repeats the cycle.

How do heat pumps work in winter? Electric heat pumps work the same way in both seasons; heat transfers outside in summer and inside in winter. The reversing valve changes the refrigerant’s direction, and the two coils reverse operations to switch between heating and cooling. In heating mode, the refrigerant absorbs heat in the outdoor coil and flows inside the house to release the heat in the indoor coil. In cooling mode, the refrigerant absorbs heat in the indoor coil and rushes outside to release heat in the outdoor coil. The defrost cycle is an additional setting that mimics the cooling process and directs hot refrigerant to the outdoor coil to melt ice accumulations. Air-source, ground-source, and water-source heat pumps are energy-efficient systems that meet your home’s heating and cooling needs.