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How Does Ductless Air Conditioning Work?

A ductless system focuses the power and efficiency of a central air and heating system into single rooms or enclosed spaces within a home without the many drawbacks of installing ductwork. For consumers asking how ductless air conditioning works, a ductless unit is actually a conventional heat pump scaled down to accommodate the cooling and heating load of a limited space. Indoor and outdoor components are connected by a single conduit that conveys refrigerant between the units and requires only a 3-inch hole in an exterior wall. The ductless installation procedure is standardized and a two-person team of HVAC professionals can usually install a ductless mini-split in a single day.

Basic Components of a Ductless System

How do ductless air conditioners work with such simplicity? The ductless system consists of an indoor unit mounted directly in the room or space to be served and an outdoor unit usually situated in the backyard or immediately to the side of the home. The indoor and outdoor components can be as much as 50 feet apart.

Indoor Unit

The inside constituents of ductless cooling and heating commonly include a downsized wall-mounted air conditioner unit. Some models may be installed on the ceiling and floor units are also available. The air handler incorporates a blower fan and a coil that contains refrigerant circulated from the outdoor unit. In cooling mode, the coil functions as an evaporator, absorbing heat energy from the room and removing humidity. In heating mode, the indoor coil disperses heat extracted from outdoor air by the exterior unit. The indoor air handler in a ductless unit normally integrates two types of filtration: a standard air filter and a plasma IAQ (indoor air quality) filter. Condensation removed from indoor air is collected by a drip pan, then drained through a line to the outdoors or plumbed into a household drain.

Outdoor Unit

Outside, a cabinet encloses the basic components of a heat pump. In cooling mode, the outdoor coil disperses heat removed from the inside of your home and conveyed outdoors by the refrigerant. In heating mode, the outdoor coil contains refrigerant that absorbs heat from the winter air, concentrates the molecules of heat energy with a compressor mounted adjacent to the coil, then moves the hot refrigerant inside to disperse warmth as it circulates through the indoor coil. In addition to the coil and compressor, the outdoor unit includes a coil fan to enhance the efficiency of the coil.

Mini-split versus Multi-split

The ductless multi-split simply expands on the possibilities of a mini-split. The capacity of the outdoor coil and compressor of a typical mini-split is often sufficient to accommodate up to five individual indoor air handler units installed in different rooms of your home. Each of these indoor units is an independent cooling/heating zone, controlled by its own individual thermostat. Installing a multi-split permits the expansion of mini-split efficiency and comfort to additional rooms in a home without the necessity to install interconnecting ductwork.

Where Ductless Is Needed

Ductless cooling and heating technology is a good match for homes in which the complexity and expense of installing ductwork for central air conditioning isn’t feasible or financially viable. When evaluating how much ductless AC costs, the savings that come from eliminating expensive ductwork and lower monthly energy bills that come from efficient design are substantial. It’s a natural match when a home has existing central or room AC, but new add-on rooms are being constructed or previously unconditioned rooms are being renovated for other purposes, such as a home office. In these cases, a ductless system answers the cooling and heating needs of the new space without extending existing ductwork or installing additional room units. In climates in which cooling and heating is required only in certain rooms, such as bedrooms and a family room but not the entire living space of the home, ductless units can be used to target just those individual spaces efficiently and effectively.

An Air Conditioner Small Enough For:

  • Server rooms
  • Condos
  • Basements
  • Garages

An Air Conditioner Quiet Enough For:

  • Hospitals
  • Churches
  • Bedrooms
  • Recording Studios

Powerful Enough For:

  • Office Buildings
  • Multi-Tenant Dwellings
  • High-Rise Buildings
  • Hotels

High-Efficiency Perfect For Everyone

When comparing ductless AC vs. central AC vs. window units, ductless technology comes out on top for two reasons. First, residential ductwork is notorious for wasting energy, leaking as much as 20 percent or more of the conditioned air that it's supposed to convey throughout your living spaces. A system that does not utilize ducts is therefore inherently more efficient. Second, in heating mode, the heat pump in a ductless system operates by simply moving heat from outdoors to the indoors, not by generating heat by combustion. Conventional gas-fired heating systems lose some percentage of the available heat energy in the combustion process as hot gases are exhausted. This is money that literally goes "up the vent." Ductless systems typically offer across-the-board energy savings of up to 50 percent, depending on local electricity and natural gas costs.