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Ductless Systems 101

What is a ductless system?


Ductless air conditioning systems are also referred to as mini split systems. They are available as straight air conditioning or as heat pumps, providing both cooling and heating. Just as split system air conditioning is comprised of two parts, an indoor air handler and an outdoor condenser, the mini split system is also divided into indoor and outdoor units but with a difference. A split system has only one indoor air handler that sends conditioned air throughout a building through a network of ducts. A mini split system delivers air to each space directly through individual air handlers. Each space to be conditioned will have its own independent unit with individual temperature control. A ductless system can be set up for as few as one space to as many as eight spaces with a single condenser. In homes requiring more than eight spaces, multiple condensers can be set up, further customizing the air conditioning design.


How do mini splits work?


The process used in with ductless systems is basically the same as with split systems. For details on the actual process please see Central Air Conditioning 101 and Heat Pump 101. Rather than having a large air handler in the basement or garage, small air handlers are located in each space to be cooled.  The most common models are mounted high on the wall but other models can be ceiling flush or recessed mounted as well as low wall or floor mounted. These units have dampers (or fins) at the top that draw room air in. The air flows across the coil which pulls the heat out before it is filtered and passed out through the dampers at the bottom of the unit. The indoor units are operated by remote controls, either wall mounted or hand held with a remote for each unit. Many manufacturers offer options for centralized control of the system as well as for WiFi control.


Why should I choose ductless air?


While ductless systems are more expensive to purchase than split systems are, they do have some advantages with regard to ease of installment, flexibility in placement, energy savings and complete, true zoning comfort. Since each space has its own air handler, each room’s occupant can adjust the temperature setting to suit their own needs. Rooms such as a kitchen, playroom or home gym may require more conditioning at times while an infant’s room may require less conditioning. With central air, there is little or no way to adjust for that without making other rooms uncomfortable. With a mini split system, adjusting a single space will not affect any other room and in rooms that are unoccupied, air conditioning doesn’t have to be wasted. This ability to condition only occupied rooms is a huge energy savings.


Since forced air heating and cooling systems require ductwork, they are less efficient. Ductwork is usually run through unconditioned spaces such as attics and basements causing some degree of cooling loss. In fact, energy.gov states that this cooling and heating loss can account for more than 30% of energy consumption of the conditioned space. Since mini splits deliver the cooled air directly into the space, the efficiency is very high.


Installing a central air system into an older home can be very difficult. Often the architecture dictates the use of large, unsightly bulkheads which intrude on the living space, lowering ceiling area and sometimes loosing cabinet spaces. Home extensions and renovations often lead to difficulties and major expenses when it comes to adding conditioning. It is not always convenient or feasible to extend existing ductwork into such spaces. Mini splits don’t have cumbersome ductwork and can easily be retrofit into older homes. The refrigerant is supplied to air handlers through small runs of line set which require only a 3" hole through the wall. When multiple floors require conditioning, line set can be run on the outside of the house and concealed with line set cover which looks like a standard down spout and can be painted to match the home’s exterior.


Mini split condensers are much smaller than traditional split system condensers so they can be more easily installed in smaller spaces. In cases such as condominiums, coops, and very small yards, mini split condensers can be mounted to the exterior wall. The air handlers can also be conveniently installed above windows or doorways, freeing up wall space. Mini splits are whisper quiet and highly efficient making them a great choice for home air conditioning. As to the cost, look for rebates and local power company incentives to offset the expense.