How Do Air Source Heat Pumps Work?

Air source heat pumps provide both heating and cooling. They operate extremely efficiently, run very quietly, and maintain very consistent temperatures. On top of that, the cost of new equipment and installation is on par with most traditional HVAC options, and they can work for many different applications in your home.

How is all this possible? How do these systems work?  Here is an overview of the basics

Moving Heat for Heating and Cooling

As indicated by the name, air source heat pumps take heat sourced from the air and pump it somewhere else. During the winter, they take heat from the outside air and pump it inside to warm up your home. During the summer, they work in reverse, taking heat from the inside and pumping it outside. The process is very similar to how a traditional AC or refrigerator works.

Mini split heat pumps have two copper or aluminum coils (one in the indoor air handling unit and one in the outdoor compressor). They also have a compressor attached to a reversing valve that allows you to switch between heating and cooling modes. When the system is heating, liquid refrigerant in the outdoor coil absorbs heat from the outside air. New heat pumps feature technology that allows them to be energy efficient even in sub-zero temps.

The heat turns the refrigerant from a liquid to a gas. Then, it moves through the refrigerant lines to the coil in the indoor air handling unit. If you have multiple indoor air handling units, each of them has its own coil for this process. The hot gas heats up the metal coil. Then, as the unit’s fan turns, air moves over the coil, the air gets warmed up, and the air releases heat into the room.

When you switch your air source heat pump to cooling mode, this process happens in reverse. The indoor coil absorbs the heat from your room, and the compressor pumps it outside. Then, the heat gets released from the outdoor compressor—that’s why you feel hot air when you stand next to an AC condenser during the summer.

Connecting the Indoor and Outdoor Units

The indoor and outdoor units of an air source heat pump are connected. Electrical lines, refrigerant cables, and very small drainage pipes run between the two systems. These lines carry power between the units. They also move the refrigerant to make the above processes possible, and they use drainage lines to get rid of condensation that builds up on the metal coils.

Using Technology to Work Efficiently

The above process has always been the way that heat pumps work, but new generations of heat pumps do this process much more effectively than older generations. By extension, they keep your home more comfortable, while also consuming as little power as possible. Here are the features that make that possible:

  • Thermostatic expansion valves – These valves control the flow of refrigerant between the indoor and outdoor units, and they also compress the refrigerant so that more of it turns from liquid into gas. Thermostatic valves ensure that the optimal amount of refrigerant moves between your coils. If too much liquid refrigerant is in the evaporator, then it will take too much heat to turn the liquid into a gas, but if too little refrigerant is in there, it won’t be able to absorb enough heat. This rule applies whether you’re trying to heat or cool your space.
  • Variable speed blowers – Traditional ACs and central furnaces generally have a fan that runs at a set speed. Either the system is on and the fan blades are turning, or the system is off and the fan is still. The indoor air handling units of air source heat pumps work with variable speed blowers, which improve efficiency and comfort. By having the fans always running, you eliminate temperature fluctuations in the room, reduce humidity, keep noise levels low, and avoid issues related to dirty coils or blocked filters.
  • Inverter technology –  Rather than using a lot of power to turn the compressor on and off, heat pumps with inverter technology stay on most of the time. The inverter makes gentle adjustments to the compressor, and this also boosts efficiency and comfort.

Note that the variable speed blowers are in the indoor units, while the variable speed compressor is outside. Pairing this technology really helps your overall efficiency. Well-designed air source heat pumps also have improved coil designs and cooper tubing which is grooved inside to increase the surface area, which helps with the heat transfer of the system.

Using Ducted and Ductless Designs

The classic design of a mini split is ductless. The outdoor compressor connects to each indoor air handling unit, and each indoor air handling unit blows out air to make the space more comfortable. These units are not designed to connect to ductwork.

However, you can use this technology with ducts. You can connect the air source heat pump to your existing ductwork and have it replace your forced air equipment, but although possible, that setup is relatively rare. More commonly, people turn to ducted air source heat pumps when they want a single air handling unit to provide heating and cooling to multiple small rooms. For instance, someone may put an air handler in their attic and then run short ducts from the air handler to each of their bedrooms.

Contact Us About Air Source Heat Pumps

At N.E.T.R., Inc., we have the highest level of dealer training for Mitsubishi and LG heat pumps, and we can help you add this technology to your home. To get help now, contact us today. We’ll connect you with a comfort consultant who can help you choose the best setup for your home and personal preferences. Or to learn more now, check out our e-book on air source heat pumps.