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Ductless Mini Splits


Ductless, Mini-Split Heat Pumps

Ductless, mini-split-system heat pumps (mini splits) make good retrofit add-ons to houses with "non-ducted" heating systems, They can also be a good choice for room additions, where extending or installing distribution ductwork is not feasible.

Like standard air-source heat pumps, mini splits have two main components: an outdoor compressor/condenser, and an indoor air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing, and a condensate drain, links the outdoor and indoor units.


The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling 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). Since each of the zones will have its own thermostat, you only need to condition that place when someone is there. This will save energy and money.

Ductless mini-split systems are also often easier to install than other types of space conditioning systems. For example, the hook-up between the outdoor and indoor units generally requires only a three-inch hole through a wall for the conduit. Also, most manufacturers of this type of system can provide a variety of lengths of connecting conduits. If necessary, you can locate the outdoor unit as far away as 50 feet from the indoor evaporator. This makes it possible to cool rooms on the front side of a building house with the compressor in a more advantageous or inconspicuous place on the outside of the building.

Since mini splits have no ducts, they avoid the energy losses associated with ductwork of central forced air systems. 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.

In comparison to other add-on systems, mini splits offer more flexibility in interior design options. The indoor air handlers can be suspended from a ceiling, mounted flush into a drop ceiling, or hung on a wall. Floor-standing models are also available. Most indoor units have profiles of about seven inches deep and usually come with sleek, high tech-looking jackets. Many also offer a remote control to make it easier to turn the system on and off when it's positioned high on a wall or suspended from a ceiling.

Split-systems can also help to keep your home safer since there is only a small hole in the wall. Through the wall and window mounted room air-conditioners can provide an easy entrance for intruders.


The term ductless means simply that no ductwork is involved. The system is comprised of two units: a slim-line outdoor condenser, and an indoor air handler. The condenser supplies coolant to the air handler through refrigerant lines that run through a small opening in the wall or ceiling and into the back of the unit. The air handler takes in supply air from the room through the front grill and dispenses the newly-cooled air back into the room. For certain models special filters are available that promote added humidity control and filtration.



  • Besides their small size, the advantages of mini splits include ease of installation, lack of ducts and flexibility of placement for heating or cooling separate rooms, which can be controlled by separate thermostats.

Other Facts

  • Mini splits reduce operating costs because no energy is lost through ducts. It's important to select the correct size and location for installation. However, it may be more difficult to find qualified installers for these systems than for regular units



  • Ductless Air Conditioning System Design

As the name implies, ductless air conditioning systems are those that do not rely on ductwork to deliver cool air. A ductless air conditioning system consists of two major parts: a small indoor air delivery unit and a larger outdoor compressor unit. On the inside of a room, the indoor component is installed near the ceiling on an exterior wall. Holes must be made through the wall to the outside, and refrigerant lines must be fed through these holes. The refrigerant lines connect to the outdoor compressor, which typically sits on a level concrete slab on the ground. The outdoor compressor is connected to a source of electricity.

  • The Cooling Process

When a ductless air conditioning system is turned on, the compressor and refrigerant stored in the outdoor unit begin working together to create cool air. Cooled air and electricity are then pumped out of the outdoor unit, along a series of refrigerant lines, into the indoor unit. The electricity delivered to the indoor unit powers a fan, which blows and distributes the cooled air throughout the room in which the system is installed. Hot air inside the room is also pumped out through the indoor units and refrigerant lines, as well as condensation that collects inside the indoor unit because of the cool air.

  • Advantages of Ductless Air Conditioning

Ductless air conditioning offers the best balance of efficiency, cooling power and value for homes that do not have existing ductwork. Many homes built before the development of central climate control were built with thinner walls that cannot accommodate standard ducts. For these homes, there are four air conditioning options; ductwork can be built into the interiors at the expense of living space and d├ęcor, flexible pipes can be installed in the walls in place of ducts, window air conditioner units can be used or ductless air conditioners can be installed. Ductless air conditioners are far more powerful, secure and energy efficient that most window units and are far cheaper and easier to install than in-room ductwork or pipe-based central air conditioning.