August 7, 2022


Mini-split in St. Louis, MO

Many of our neighbors here in the St. Louis area have a ducted furnace as well as a separate air conditioning system. It can be difficult to have two separate systems to maintain and repair. There has been a lot of buzz in the HVAC world about ductless heat pumps, so many ask us at Scott-Lee Heating Company if a ductless heat pump would be a good choice for our area and climate. People have heard that these systems can provide both heating and cooling and are thinking that it might be easier to have just one system that performs both functions.

What Is a Ductless Heat Pump?

A ductless heat pump is also sometimes called a “mini-split” system. These are units that often provide both heating and cooling year round. They are ductless because they don’t have the large, forced-air ducts that you likely have in your home. Instead of ducts that supply air through vents throughout your home, these systems rely on passing refrigerant through small diameter lines. There is an outdoor unit and one or more indoor units. The indoor units are called “heads.”

A ductless heat pump, unlike your ducted furnace system, can provide targeted heating or cooling to different zones in your home, depending on where you have decided to place the heads. If you are not using the bedrooms during the day, you can shut off or lower the amount of heating or cooling provided to those rooms while still providing heating and/or cooling to other rooms currently in use. Also, you can literally heat one room and cool another at the same time. The ability to regulate the heating or cooling in each zone separately makes them very energy efficient, saving you money each month on your heating and cooling bills.

How It Works

In order to understand how one unit can heat your home in the winter and cool it in the summer, we need to look at the parts of the system. Between the heads and the outdoor unit, there are just a few lines. One line contains the refrigerant. Another line is the electrical wiring that supplies electricity between the outdoor unit and the heads. There is also a line that contains the condensate to send excess water outdoors. These lines only take a three-inch diameter hole in order to go through walls, floors and ceilings.

One of the great things about the electrical functioning of ductless heat pumps is that they turn your household AC, or alternating current, to DC, or direct current. This allows these units to run more energy efficiently on kilowatt hours than a central air conditioning system that simply uses AC.

The secret to the magic of being able to cool in the summer and heat in the winter is the refrigerant. In order to understand how this helps both heat and cool, you need to know that refrigerant has an incredibly low boiling point. It boils in temperatures well below freezing. Refrigerant circulates through a ductless heat pump, moving in a cycle from the outdoor unit to the indoor units. When refrigerant is liquid, it can absorb heat. When it is a gas, it can release heat.

The state of the refrigerant is controlled by the action of the compressor that compresses the molecules of the refrigerant to make the temperature of the refrigerant hotter. Depending upon whether the unit is in a heating or a cooling cycle, the refrigerant is either used to release heat through the outside unit’s coil and fan or inside your home when you need to provide heating.

There is an evaporator coil in the indoor units of the ductless heat pump system. When in cooling cycle, the refrigerant flows through the evaporator coil, absorbing heat. The indoor unit also has a fan that circulates the cooler air into the room. Then, the refrigerant flows to the outside unit. There, heat is released by the condenser coil and a fan.

It is hard to understand how heat is absorbed from the outside air in winter to be conditioned and distributed in your comfort zones in winter. Again, realize that refrigerant boils at a very low temperature. Thus, the refrigerant can indeed absorb heat and become gaseous in winter from the outside air. This heat is then sent through the refrigerant lines to be released by the indoor coil and blown out into your room in the winter.

Best Use Cases for Ductless Heat Pumps

Ductless heat pumps are best utilized in homes that have a closed floor plan. They are not as well suited for homes that have large rooms or open floor plans. Each indoor unit has a limit to its BTU or heating and cooling capacity measurement. Larger rooms would need multiple indoor units, which is not as energy efficient.

They are also best utilized in homes that do not already have ductwork installed. It is sometimes very difficult and expensive to install ductwork into older homes for the first time. Another really good use for ductless heat pumps is when you have an outbuilding, a granny house or an addition that is not already served by your ductwork. Then, you can have a hybrid system where most of your home is served by central air and heating but a portion is served by a ductless heat pump.

These units don’t have the loses of energy you will find in ducted systems. In fact, the Department of Energy states that ducted comfort units can lose as much as 30% of their heating capacity when the ducts run through areas of your home that you are not conditioning. Their flexibility is also a big advantage because you can create zones with indoor heads in any location you desire.

What About Using Ductless Heat Pumps in the St. Louis Area?

Ductless heat pumps perform well in our St. Louis area in a properly sized home because our winters are milder. Ductless heat pumps are best utilized for heating in climates that do not stay well below freezing for many days each season. In well below-freezing weather, they are not as efficient in extracting heat, even though their refrigerant does have a very low boiling point.

Call Us for All of Your Heating and Air Conditioning Needs

At Scott-Lee Heating Company in St. Louis, our neighbors have been counting on us to take care of all of their heating and air conditioning needs for over 40 years. We provide heating and air conditioning installations, maintenance and repair services. We guarantee heating and air conditioning repair service within 24 hours, whichever day you call. Our technicians are NATE certified, and we are a Lennox Premier Dealer. The Better Business Bureau company (BBB) has given us a rating of A+.

We are pleased to offer financing of installations on approved credit through Synchrony as well.

Call us today at Scott-Lee Heating Company in St. Louis with any questions you have about ductless heat pumps. We are here to help you figure out what is best for your home and floor plan.