A Basic Understanding of How a Heat Pump Functions

January 12, 2022
Heat Pump in North Kansas City, MO

A heat pump transfers heat from one location to another. The basic operation of air and ground source heat pumps is the same. Ground source heat pumps move heat between the ground outside and the inside air. Heat pumps that get heat from the air exchange heat between inside and outside the home.

Your Heat Pump’s Inner Workings

Heat pumps, unlike a furnace, do not create heat. Rather, their sole purpose is to transfer heat between two locations. A furnace uses a flame, a heat exchanger, and a blower to create and distribute heat in a house. Heat pumps work by absorbing heat from outside and bringing it inside the home. It can do this even when it is moderately cold outside.

When you switch your heat pump to cooling mode, it absorbs the heat from inside of your house and releases it to an outdoor unit. It works similarly to your AC unit.

There are several types of heat pumps available. When determining the system that is right for your property, you should consider your local climate, the size of your house, and the design of your home to make the best decision. HVAC technicians at Summit Heating & Cooling can happily help you find the right-sized heat pump for your residence.

The Parts That Make Up a Heat Pump

A typical heat pump has two primary components. The outside unit shares similarities to the external unit of an air conditioner. The indoor unit, or the air handler, is located in the home. Within each of these units, there are subcomponents that make them function.

With the outdoor unit, there is a fan and a coil. The coil can work as an evaporator when heating or as a condenser when in cooling mode. The fan makes heat exchange possible by blowing cool air over the coils.

The air handler also has a fan and a coil. When in cooling mode, the coil functions like an evaporator. In heating mode, it operates as a condenser. The fan moves the air across the coils and pushes it through the air ducts in your home.

Refrigerant runs through the coils and absorbs or rejects heat. This is what allows for heat exchange. The refrigerant is pressurized by the compressor as it travels through the system. A reversing valve allows the system to reverse the refrigerant flow, letting the system function either as a heating unit or a cooling unit. Finally, the refrigerant’s flow is regulated by an expansion valve as it travels through the system. This allows the refrigerant to reduce pressure and temperature.

Can Heat Pumps Work When It Gets Cold Outside?

Heat pumps can work in moderately cold temperatures. It would have to get extremely cold for a heat pump to stop working altogether.

Various models of heat pumps are assigned different ratings for how cold it can be outside before they stop working. Heat pumps are rated based on their output. For example, if a heat pump is rated to provide sufficient heat at 15 degrees below zero Fahrenheit and it is 30 degrees outside, then the pump should produce 100% of its output.

However, as the temperature drops, the output will also start dropping. When the output starts dropping, the heat pump will have to exert itself harder to keep your house at the temperature you want. You can compare it to needing to put your foot on the gas to maintain a set speed when driving uphill.

In older houses with insufficient insulation that have large amounts of heat loss or drafts, a heat pump will need to work harder because of the rapid loss of heat caused by these issues. However, newer homes with excellent insulation are built to fight against heat loss. In this case, the heat created by the pump is kept in the house, allowing the heat pump to function with greater efficiency.

How Does a Heat Pump Work in Heating Mode?

In heating mode, a heat pump works just like in cooling mode. The only difference is that the refrigerant flows in the contrary direction thanks to the reversing valve.

As a result of the reversal, outside air becomes the heating source, even if outdoor temperatures are cool, and the heat produced warms the home. The indoor coil becomes the condenser. The outside coil works as an evaporator.

The basic physics remain the same. The outdoor unit absorbs heat energy via the cold liquid refrigerant. The heat turns the refrigerant into a gas. Pressure turns the cold gas into a hot gas. The heated gas travels to the indoor unit and is cooled by the air passing over the coils. This heats the air, which is distributed through the house. The hot gas becomes a warm liquid. The heated fluid is then depressurized as it travels to the outdoor unit. It becomes a cool liquid, starting the process again.

How Does a Heat Pump Function in Cooling Mode?

A heat pump works by transferring heat. One of the basic principles of heat transfer is that heat naturally wants to travel to areas that have lower temperatures and pressure. A heat pump will then expose the heat to lower pressure and cooler environments, allowing the heat transfer to happen naturally. This is the core of a heat pump’s function.

First, the liquid refrigerant travels through the expansion device of the indoor coil. During cooling, this coil functions as an evaporator. Indoor air is distributed over the coils. The refrigerant absorbs the heat energy. The result is that cooled air is blown through the home’s ducts. As the refrigerant absorbs the heat energy, it rises.

Next, the refrigerant in gas form passes through the compressor, pressurizing the gas. The gas heats up when it is pressurized. The pressurized refrigerant goes through the coil system to the outdoor unit.

The next step involves the outdoor unit’s fan, which pushes air over and around the coils. In this case, the outdoor unit serves as a condenser. Since the outdoor air is colder than the compressed gas refrigerant traveling through the coils, the refrigerant heat is transferred to the air outside. As this happens, the refrigerant condenses into a liquid as its temperature cools. The heated refrigerant in liquid form is then pushed to the indoor unit’s expansion valve.

Finally, an expansion valve reduces the heated liquid refrigerant’s pressure, causing it to cool down drastically. The cool refrigerant is then pumped back into the evaporator coil, starting the process again.

Personalized Heating and Cooling

Our team has over 200 years’ worth of combined experience, and we are equipped to take on both large commercial projects and small residential jobs in Kansas City. We maintain, install, and repair water heaters, ductless mini-splits, air conditioners, and heating units.

Our technicians pride themselves on running diagnostics and repairing HVAC systems of all makes and models. If you decide to replace the HVAC system in your home or business, we are the team you should turn to. Our installation department is second to none. Contact Summit Heating & Cooling today to learn more about our stellar services.

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