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ThermAll Heating, Cooling & Electric Blog

How Does a Heat Pump Change Between Heating and Cooling Mode?


Heat pumps are versatile HVAC systems that can both heat and cool spaces efficiently. But have you ever wondered how they seamlessly switch between heating and cooling modes? Understanding the mechanism behind this transition can provide insight into the functioning of these devices.

ThermAll Heating, Cooling & Electric provides heat pump service in Yakima, WA, and is knowledgeable in the workings of heat pumps. In this article, we will delve into the inner workings of heat pumps and explore how they switch between heating and cooling modes.

Heating Mode

When a heat pump is in heating mode, it extracts heat from the outside air (even in cold temperatures) and transfers it indoors. This process involves the following steps:

Refrigerant Absorption: The heat pump contains a refrigerant, typically a fluid with a low boiling point. In heating mode, the refrigerant absorbs heat from the outdoor air through the outdoor unit’s coils.

Compression: After absorbing heat, the refrigerant is compressed by the compressor, which increases its temperature and pressure. This compression process is essential for raising the refrigerant’s temperature to a level suitable for indoor heating.

Heat Exchange: The hot, pressurized refrigerant is then circulated to the indoor unit, where it passes through a coil. Here, the refrigerant releases heat into the indoor air, warming it up.

Cooling Mode

Switching to cooling mode involves reversing the flow of refrigerant to absorb heat from indoors and release it outdoors. Here is how it works:

Reversing Valve: Heat pumps are equipped with a reversing valve, which changes the direction of refrigerant flow. When switching to cooling mode, the reversing valve redirects the flow of refrigerant so that the outdoor coil functions as the evaporator, and the indoor coil acts as the condenser.

Refrigerant Evaporation: In cooling mode, the refrigerant absorbs heat from the indoor air as it passes through the indoor coil. This heat absorption causes the refrigerant to evaporate into a low-pressure, low-temperature gas.

Compression and Heat Release: The now-gaseous refrigerant is compressed by the compressor, increasing its temperature and pressure. As a result, the refrigerant releases heat to the outdoor air through the outdoor coil.


One of the biggest advantages of a heat pump over a standard heating, ventilating, and air conditioning (HVAC) unit is that there is no need to install separate systems to heat and cool your home. Heat pumps also perform very efficiently, because they simply transfer heat rather than burn fuel to generate it. This makes them greener and more eco-friendly than a gas-burning furnace.

Heat pumps are remarkable HVAC systems that efficiently provide both heating and cooling by simply reversing the flow of the refrigerant. Whether extracting heat from the outdoor air for heating or removing heat from indoors for cooling, the mechanism remains fundamentally the same, with the refrigerant playing a crucial role in heat exchange. Understanding how heat pumps transition between heating and cooling modes can help users appreciate their versatility and energy-saving capabilities.

Contact ThermAll Heating & Cooling & Electric: We are “Your Home Comfort Hero!”

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