What is a Mini-Split Air Conditioner

A “split” air conditioner consists of two main parts: the outdoor unit and the indoor unit.

A mini-split system is therefore “split” into the compression and expansion stages of the refrigeration cycle. Refrigerant lines and electrical wires connect the condenser to the evaporator. The outdoor unit contains a compressor which pumps the refrigerant to the indoor evaporator where it expands and cools. A fan behind the evaporator coil blows the cool air into the room. Because the coil and fan blow directly into the room, the term “ductless” applies because no distribution system is required.


How a Mini-Split Air Conditioner different from other AC Units

Like central air systems, but unlike a window air conditioner, also known as a “self contained” or one piece, a mini-split air conditioner or a mini-split heat pump consists of two separate components including an outdoor condenser/compressor and an indoor evaporator, or air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing and a condensate drain, links the outdoor and indoor units.

Mini splits have numerous potential applications in residential, commercial and institutional buildings. The most common applications are in multifamily housing or as retrofit add-ons to houses with non-ducted heating systems, such as hydronic (hot water heat), radiant panels and space heaters. They can also be a good choice for room additions and small apartments, where extending or installing distribution ductwork is not feasible.


Benefits of a Mini-Split Air Conditioning System

This kind of air conditioner has many advantages over traditional air conditioners including quiet performance. The parts of the air conditioner that make the most noise are the compressor and the fan that cools the condenser, which in a split system, are located outside of the room being cooled and therefore the major sources of noise are removed, unlike with window units.

Other advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. Central air conditioners usually cool an entire area, but mini splits can be more selective and heat or cool specific areas and individual rooms. Many models can have as many as four indoor air handling units (for four zones or rooms) connected to one outdoor unit. The number depends on how much heating or cooling is required for the building or each zone, which in turn is affected by how well the building is insulated. Each of the zones will have its own thermostat, so you only need to condition that space when it is occupied, saving energy and money.

Ductless mini split systems are often easier to install than other types of air conditioning systems. A ductless mini-split system is similar to a central air system in that the evaporator is “split” from the condenser, but unlike a central air system, no duct work is required. The hookup between the indoor and outdoor units  generally requires  only a two- to three-inch hole through the wall for the conduit, Also, most manufacturers of this type of system can provide a variety of lengths of connecting conduits so that if necessary, you can locate the outdoor unit as far as 50 feet from the indoor evaporator.

Because there is no ductwork required, mini split systems are not only easy to install but also more economical and better for the environment. The ductwork required for many traditional air conditioning units generally increases energy expenditures, as many centralized AC units lose a lot of energy due to heat exchange in the air duct system. So, without a duct system, there is very little opportunity for heat or energy loss in a split air conditioning system. Duct losses can account for more than 30% of energy consumption for space conditioning, especially if the ducts are in an unconditioned space such as an attic.

A mini-split heat pump will also supplement an inadequate heating system and add comfort to a room. However, as in the case with all heat pumps, it may not be sufficient and might require an auxiliary heating source. This depends on the climate you reside. Some areas require considerably more BTU of heating than cooling, so the proper size air conditioner may not be the proper size heat pump. Over sizing is not a good idea for two reasons. You will loose efficiency by running a large air conditioner than needed. And, over-sized cooling will cool, but not dry effectively.


Disadvantages of a Mini-Split Air Conditioning System

The primary disadvantage of mini splits is their cost. Such systems can cost anywhere between $1,500 to $2,000 per ton (12,000 BTU per hour) of cooling capacity, which is about 30% more than central systems, not including ductwork, and may cost twice as much as window units of similar capacity.

An installer must correctly size each indoor unit and judge the best location for the installation. Oversized or incorrectly located air-handlers often result in short-cycling, which wastes energy and does not provide proper temperature or humidity control. Too large a system may also cost more money and use more energy to operate.

Although there will be more control of cooled areas, refrigerant lines and electrical wires must be installed from each evaporator to the condenser. There must also be a place to drain condensate water near the outdoor unit. Unlike window and central air conditioners which have brazed joints, most mini splits have flared copper to brass refrigerant connections, making it possible to loosen and leak. Because the refrigerant lines come pre-attached to the evaporator, mini splits can also be more difficult to “rough-in” on new construction or remodels. Mini splits are simpler to install on finished wall.

The indoor section of a mini split is good sized, however physically locating it can present a problem at times. Built-ins, windows and doors and décor can also be implements to prime locations and some people may not like the appearance of the indoor part of the system.  While less obstructive than a window room air conditioner, they seldom have the built-in look  of a central system.



The indoor unit will most likely have an air filter, which will require periodic cleaning or replacement, depending on how often the unit runs. The outdoor unit should be kept clear of plants and debris. It would not hurt to have a professional HVAC technician clean and test the condenser, which we recommend yearly. If you would like to have this done, Call ACE HI today at 970-667-0300. We service Fort Collins, Colorado and Loveland, Colorado.


A split air conditioner is an efficient and cost effective way to cool your home, however, qualified installers and service technicians for mini splits may not be easy to find. It should be noted that the initial cost  of this type of air conditioning unit is significantly higher than a window unit and does require professional installation. The amount you will save on your energy bills as well as the longevity of the unit will make it worth your while in the end.