The Key Feature of Mini-Splits

Mini splits are a great solution to a wide variety of installation challenges giving contractors the ability to put air conditioning — and heat, with heat pump models — in locations that previously seemed impossible. And as awareness of the mini-split’s advantages increases, new applications are being developed practically every day.

Basically, a mini-split does away with the need for ductwork. Like a regular split-system air conditioner or heat pump, the condenser is located outdoors; one or more air handlers are placed indoors. The two are connected by electrical and refrigerant lines that run through a small hole in an exterior wall, generally 3 inches in diameter or less.

Total Zone Control

In addition to eliminating the need for ducting, one of the other big advantages to mini-split systems is true zone control. The air handler is dedicated to the room being conditioned and is controlled by a wireless remote. That room can be kept at temperature and humidity levels that are different from the rest of the house or building.

Multiple zone systems offering the same advantage are also available. In this type of an installation, the single condenser handles two or three air handlers. Each air handler is independently controlled, with its own remote and electronic-based climate controls to regulate temperature and humidity levels, as well as airflow. Units in a bedroom and a home office, for instance, can be programmed for different hours of operation with the 24-hour timer, or two classrooms situated side by side can be set at different temperatures.

Boundless Applications

Ductless air conditioners are practically limitless, noting that ductless mini-splits were ideal for any place where installing ductwork is difficult, prohibitively expensive, or impractical. Residential and commercial applications are both candidates for mini-splits, whether they are new construction projects or existing buildings. Common applications include historic homes; vacation homes and cabins; schools; churches; nursing homes; residential room additions; remote offices, such as those inside a warehouse or factory; utility transfer stations; arena skyboxes; computer rooms; ATMs; and homes with hydronic heat.

In addition to preserving the exterior appearance of a building, mini-splits offer greater security than a window-mounted installation, since the only access to the interior is through a 3-inch hole. On the inside, air handlers are low profile at about 7 inches deep and neutral in color.

Quiet And Efficient

Another plus for mini-splits is that they are surprisingly quiet. Many people don’t even realize they’re running.

High-tech features can also make mini-splits inviting. The tangential fan design moves large volumes of air at low fan speeds, resulting in reduced energy usage and operational sound. A microprocessor continuously adjusts fan speed and louver direction for a gentle, breeze-like effect.

From the contractors’ perspective, it’s nice to know that most mini splits are easy to install, producing a better profit potential. The typical mini-split single-zone installation takes on average three to four hours. With no ductwork to deal with and no time-consuming air balancing, installation can truly be called “fast and easy”.

Ductless air conditioning systems have been around North America for almost 20 years. Mainly considered a niche item, they worked great in old houses or historic buildings that needed cooling but had no space for ductwork. Or, they were used when spot cooling was required, or perhaps when one room needed a little more cooling than the rest of a structure.

But in the last two or three years, mini-splits have enjoyed wider popularity, due in part to the fact that a whole generation has now lived with them and found them to work well. Word of mouth has spread, inducing more people to check out the benefits of mini-splits. Some owners of new houses are even requesting multiple mini-split systems as opposed to one central a/c system.


Another mini-split advantage is its energy efficiency. “People are understanding that true indoor comfort costs include operation and longevity expense in addition to the initial cost.

One of the reasons a mini-split can save energy is that it can be used to cool one zone of a building. In a house, for example, residents often gather in one place for the majority of the time.

However, homeowners should not use a mini split system the same as, say, a window air conditioner. Mini splits are sometimes better to be left on when it’s really hot and humid out. You can put these on a function called the auto mode, which is very cost effective, and it will allow you to keep the room at a temperature in either cooling or in the dry mode, or in whatever mode it needs to maintain the temperature.

Another benefit includes having the air handler section in the living space (as opposed to a central system, which usually relies on a thermostat placed in a hallway or some other place that gives an average temperature of the entire house). With a mini split, the temperature sensor is in the living space, and there will only be a plus or minus 2 degrees F difference in each zone.

In addition, the evaporator coil, which is also in the living space, dries the air better, as it has a 35 degree temperature (30 degrees delta T,) rather than the standard 45 degrees (20 degrees delta T) on a central system evaporator. The dewpoint is achieved quickly, so the discharged air is drier and cooler. With less humidity in the air, occupants have a tendency to turn up their system set points by 2 to 4 degrees, resulting in even more energy savings.

Having a mini-split in an occupied space often brings up concerns about the level of noise. This isn’t an issue, because the evaporator coil features a cross-fan impeller designed with staggered vanes of different lengths. This modifies the sound generated by the air crossing the vanes. Some new designs have wall-mount units operating at under 30 dB at high speed.

As for the concern about condensing units being placed close to a structure, owners need not worry. A lot of people are not aware of how unbelievably quiet the outdoor units are and how they can really be put close to areas that they’re in, how little they impact the area that they’re in.

Because owners are concerned about noise, contractors have a tendency to overextend the amount of line set between the indoor and outdoor units; that hurts the mini split’s performance. Keep the indoor and outdoor units as close to each other as possible because more energy will be saved that way. The system will run more efficiently.


As can be expected, mini split systems are not sized the same way (using cfm as the measurement) as a central a/c system. Where some contractors make a mistake in determining the size of a mini-split is by counting the cfm. Mini-splits average about 250 cfm per ton, rather than the 400 cfm per ton of standard central systems.

As a result, a common problem is oversizing. Interestingly enough, mini split systems usually work better when they’re slightly undersized. If our systems are slightly undersized they’ll do a much better job, not only because they’ll run longer but because they’re dealing with latent heat; the evaporator temperature is so low, they’ll do a great job of moisture extraction.

Another issue is the location. A mini-split’s fan blows constantly, allowing the entire area to circulate, mixing the air and eliminating temperature stratification. For this reason, the system should be put in a place that’s going to provide a constant good sweep of the air, while not blowing air directly onto occupants or directly into a wall. You want to have at least 15 to 20 feet in front of the unit, so the air returning is indicative of the temperature in the entire room.

Another benefit is that the first cost of a mini split is now becoming comparable to more traditional air conditioning equipment. Consider that the rest of the world, which historically has much higher energy costs than the United States, has used this technology for the last 30 years. Maybe it’s worth taking the time to check out mini splits a little more closely.