mini-splits: ductless air conditioners

Ductless AC - or mini-split air conditioning, or simply mini-splits – is a good alternative to central air conditioning, especially for small apartments, room additions and homes without ducted systems.

Elements of mini-splits

Like central air conditioners, mini-splits use an outdoor condenser unit to run power and the refrigerant elements; they also involve small indoor wall-mounted fans, with each indoor unit connected to the outdoor through conduits.

Instead of mounted in a window like many room/window AC, the ductless units are installed anywhere on the walls.

The number of indoor units depends on cooling or heating needs, but most models have three or four indoor air fans that can be installed in different rooms, all linked to the outdoor unit.

Advantages of ductless air conditioning: Zoning

The big advantage of ductless is their flexibility and small size. The system can be dedicated to each space, allowing an easy adaptation to the needs of individual rooms (zoning). Since each indoor unit has its own thermostat, the system may operate only where needed, saving energy.

Besides, by avoiding the use of ductwork, ductless AC also avoid energy losses associated with central air-conditioning: duct losses can be very significant, especially when ducts are in unconditioned spaces like attics.

Ductless AC is also quieter than a central or window AC (the refrigeration takes place outside).

Disadvantages of ductless air conditioning

The main disadvantage of ductless AC is its higher initial investment. Ductless AC prices are decreasing, but they still are higher than similar room AC units.

Prices between $700 and $1,500 per ton (12,000 Btu per hour of cooling power) are now common.

Comparatively to central air conditioning, the higher initial investment can be offset by lower operating costs and energy savings.

Installation of mini-splits

Mini-splits AC should be correctly sized and located. A too large system has the same disadvantages of oversized room AC systems (see: Air conditioners Oversizing and undersizing). Wrongly located air-handlers can also cause short-cycling, with resulting wastes of energy and losses of performance.

Ductless mini split systems are easy to install but there are few qualified installers. Most installers are accustomed to the most conventional heating and cooling systems, and often refuse to recommend ductless systems.

In most cases installation involves a simple wall hole (3 inch/8 cm) to connect the outdoor and indoor units. The connecting conduits are provided with a large variety of lengths, which allows locating the outdoor unit at the most convenient walls of the building.

Ductless systems manufacturers offer a large flexibility in interior design options: the indoor air handlers can be mounted on a ceiling, suspended on a wall, or placed on the floor (in the case of floor-standing models).