How Does a Heat Pump Work?

Have you ever asked yourself how something works? Well, in this video we’re going to see how a heat pump actually heats and cools your home.

Hi, my name’s Bryan from Fire & Ice. The modern air conditioner was invented well over 100 years ago in 1901. By 1948 the ability to produce heat through the same methods was discovered. In this video we’ll take a look at what heat pumps are, how they work, and the factors that can affect their performance.

What is a heat pump HVAC system?

Heat pumps are unique because they are able to both heat and cool. While they may look like an air conditioner, they differ in a number of ways. The heart of every heat pump is the outdoor unit. Inside is the compressor, fan, condenser coil, and reversing valve. The indoor unit consists of the evaporator coil. Running between the two units is the line set which consists of a liquid and suction line. And in order to circulate the air inside your home a blower is needed which is typically found in an electric air handler or inside a gas furnace. The last thing to complete the system is a thermostat, which allows for all the pieces to communicate.

How does a heat pump work?

Now that we know what a heat pump system is made of, let’s look at how they all work together to provide heating and cooling for a home.

Like an air conditioner, a heating and cooling cycle works thanks to thermodynamics and some physical changes the refrigerant goes through as it runs through the system. In other words, the refrigerant inside the line set goes from a liquid to a gas and back again. And this process allows heat to be absorbed from inside the home and dissipated outside to cool or take heat from the outside and pump it inside. See what I did there?

Let’s take a moment to see how this works. Whether or not you’re heating or cooling both processes start the same. When the indoor temperature goes beyond the thermostat’s set point a call for heating or cooling is sent to the outdoor unit and to the furnace’s blower. 

For the sake of simplicity, let’s look at the cooling side first. Outside, the compressor takes the refrigerant via the suction line and compresses the refrigerant down. At this point the refrigerant is in a cold gaseous state and as it’s compressed down the pressure increases causing the refrigerant to become very hot. The compressor also pumps the refrigerant through the condensing coil. As the heated refrigerant runs through the condenser the heat is dissipated by the fan inside the condenser and absorbed by the ambient outdoor temperature. As the refrigerant cools it goes from a hot gas to a liquid and travels through the liquid line to the evaporator coil inside your home.

Inside, the blower in your furnace or air handler has been collecting the hot unconditioned air throughout the house via the return air ducts. The air is then pushed over the evaporator coil located above the furnace. As the refrigerant travels through the liquid line from the condenser through the evaporator coil the temperature is much cooler than the air blowing over it. During this phase the refrigerant absorbs the excess heat in the air while the conditioned, cooler, air continues to blow throughout the rest of the house. By the time the refrigerant exits the evaporator coil the liquid has evaporated back into a gas where it continues its cycle. The whole system runs until the thermostat senses the desired temperature and sends a signal to turn off the cycle.

As for the heating process, it’s really the same thing but in reverse. The evaporator coil becomes the condenser and vice versa. Effectively the heat from ambient temperature outside is absorbed and is distributed over the indoor coil warming the air. In fact, some modern heat pumps are able to produce heat in temperatures well below freezing, since there’s still technically some heat in the outside air.

What factors affect your heat pump’s performance?

There are three main factors that determine a heat pump’s performance: capacity, efficiency, and features. First is the size, often referred to as tonnage. It’s important to get the right sized heat pump, since having one that’s too powerful or not powerful enough can create long-term mechanical issues.

The next factor is their efficiency. Unlike air conditioners, heat pumps have two efficiency ratings. One for heating and one for cooling. For heating they use a Heating Seasonal Performance Factor or HSPF and a Seasonal Energy Efficiency Ratio or SEER for cooling. 

Both ratings measure the amount of energy used during the average heating and cooling season. With both numbers the higher the rating the better its efficiency and associated cost savings. Most heat pumps on the market are rated between 7.7 and 11 HSPF and between 14 and 22 SEER.

Last are the features and benefits each heat pump has to offer. There are tons of options to choose from and it can be a bit overwhelming to choose. A trusted HVAC partner can help you figure out which is best for you, like whether or not you need a single-stage or multi-stage unit.

What to do next?

Let’s talk about what to do next. If you’d like to find out more information on heat pumps or other heating and cooling solutions visit our learning center at the top of the screen. If you’d like to schedule a time to discuss cooling options for your home, click the free estimate to schedule a time for a free in-home estimate. Thank you for watching and we look forward to making your day better.