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How Does A Heat Pump System Work? (Simplified Explanation)

Updated: Apr 17, 2023

Have you heard of heat pumps? They're growing in popularity for home use. How do they work though?

Instead of burning fuel or putting electricity through wires to create heat, equipment that makes use of heat energy ALREADY IN THE AIR to redistribute heat at efficiencies ranging from 150% to 700%. This type of equipment is called a heat pump. Heat pumps can be part of many different system configurations; they greatly expand number of heating/cooling options available.

The basic principle behind heat pump operation is that when any gas is squeezed, it heats up; conversely, but when a gas is allowed to expand, it cools down. Consider pumping up a bicycle tire if you have in the past. After you pump up the tire, the pump and tire valve are both much warmer. If instead you release a bunch of air from a bicycle tire, the tire valve gets cold quickly. A heat pump uses the same principle.

A heat pump is a closed loop of tubing in which gas is compressed in one location, moved to a second location, allowed to expand within the tubing, and pushed along back to the starting point to repeat the cycle. When the gas - which we refer to as the refrigerant - is compressed at the first location, it heats up; the heat is released to the environment by radiation and conduction. When the gas expands at the second location, it cools; heat is absorbed from the surrounding environment by radiation and conduction. Any air that is above "Absolute Zero" (-273°C / 0°K / -460°F) has SOME heat energy, so heat may be pulled INTO the home even in winter to provide heating or be pulled OUT of the home in summer to "provide cooling".

The energy we use to operate the pump that moves the refrigerant and to operate the compressor which compresses the refrigerant is minimal. It is a TINY amount compared to the heat energy gained and released by compressing and expanding the refrigerant, and that's enough to warm up or cool down the house. We move several times as much HEAT ENERGY as the amount of KINETIC ENERGY that we use to pump and compress the refrigerant. This relative advantage is why we say a heat pump has more than 100% efficiency and why it saves energy compared to other heating systems.

Even if the temperature where you're trying to pull heat from is very low (e.g. outside during cold winter weather), the refrigerant gas can be compressed enough to generate enough useful heat to be used elsewhere.

In summary: a heat pump has a portion which is hot (compressor + evaporator) and a portion which is cold (expansion tank and condenser). One portion of the system will often be a separate unit sitting outside your house; an automatic valve that controls the refrigerant flow will determine if the indoor unit is giving off heat or sending heat to the outdoor unit.

In my article "What is the Cheapest Way to Heat and Cool Your Home?", I explain and compare all the different systems of heating and cooling. I also discuss mini-split heat pumps, heat pump vs furnace and heat pump vs air conditioner, whether or not a heat pump is enough to heat a house, and if heat pumps are better than furnaces.

If you're considering a heat pump system for a new house or are remodeling your home and are curious about how heat pumps fit into the design, please book a free Diagnostic Session.


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