What is a Heat Pump and how does it work?

You’ve probably heard of the term or maybe you have one currently installed in your house, but what exactly is a “heat pump?”


This article gives an overview of what a heat pump is and how it works!

A heat pump often looks the same and gives the same outcome, but in most cases operates more efficiently than a traditional air conditioner. The difference is found in the components that cool and heat your house. Both an air conditioner and heat pump use refrigerant to move heat from inside your house to outside in cooling mode. It’s important to note that providing cool air is predicated on the removal of heat from inside your house. The advantage of a heat pump is that it doesn’t rely on a furnace to heat your home in the wintertime like an air conditioner does. A heat pump cools and heats your home efficiently.


How does a heat pump remove heat?

Another term you’ve likely heard of is “refrigerant.” Hopefully you’ve never experienced a refrigerant leak in the middle of the summer, but if you have, you know how crucial the product is. Side note - it’s important to have your refrigerant levels checked as part of a routine maintenance inspection - refrigerant is responsible for the removal of heat from inside your house during cooling mode. It absorbs heat inside, carries it outside, and dispels it into the outside atmosphere.

The Refrigerant Flow Cycle


Refrigerant travels through an expansion valve at the evaporator coil (located in the air  handler, often in your attic or crawl space) in a cool, liquid state. As the air from inside your home travels through the ductwork and across the cold evaporator coil, the refrigerant absorbs the heat energy and evaporates into a gas. Think back to your middle school science classes – when a liquid heats up, it turns to gas.



The refrigerant continues to travel, now toward the outdoor unit’s compressor. “Compressor” is a great name for the part because it compresses the gas, heating it up as it moves on to the outdoor condenser coil.



The fan in the outdoor unit moves air across the condenser coil, simultaneously cooling the hot gaseous refrigerant. This process cools the refrigerant down, so much so that it turns back into a warm liquid state. The heat (from inside your home) the refrigerant was carrying, is dispelled into the outside air via the outdoor unit’s fan. If you ever put your hand over the outdoor unit fan, you should notice the air is warm – now you know why.



The warm liquid refrigerant travels back to the expansion valve where it is metered and de-pressurized. This process cools the refrigerant significantly, allowing it to be a cool liquid when it hits the evaporator coil. The room-temperature air from your ductwork’s return system blows over the cold evaporator coil and travels through the supply ducts, giving you a blast of cool air.

What about heat-mode?

 Now that you know how refrigerant flow works, it’ll be easy to understand how a heat pump can provide cool air in the summer and warm air in the winter. A heat pump system has a nifty part called a “reversing valve.” The reversing valve is responsible for switching the flow of refrigerant. Because of this valve, the refrigerant can travel in the opposite direction and provide heat in the winter. Believe it or not, refrigerant captures heat from the outside winter air, and moves it inside your house. The aforementioned evaporator coil and condensing coil switch roles and continue the refrigerant cycle.


Do you feel like an expert yet? Even if you don’t, the next time you are getting “tech talk” from an AC repairman, you’ll better be able to understand what they’re saying. At Speir Heating and Air, we believe in educating our customers so they can make decisions that best fit their specific needs. A heat pump is a great option for our area of the country. Typically, our winters don’t get cold enough to need a gas furnace, however there are some applications where gas furnaces are the preferred choice. It’s important to have all options available to you when deciding on a new system. Our staff is fully trained to help you along the way!