Ductless Mini Splits
Ductless, mini split-system air-conditioners (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 (wood, kerosene, propane). They can also be a good choice for room additions and small apartments, where extending or installing distribution ductwork (for a central air-conditioner or heating systems) is not feasible.
Ductless, mini-split-system heat pumps (mini splits), as their name implies, do not have ducts. Therefore, they make good retrofit add-ons to houses or buildings with “non-ducted” heating systems, such as hydronic (hot water heat), radiant panels, and space heaters (wood, kerosene, propane). They can also be a good choice for room additions, where extending or installing distribution ductwork is not feasible.
How Ductless, Mini-Split Heat Pumps Work
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. Some models have multiple air handling units that all connect to one outdoor unit. Each air handling unit is assigned to a different zone or room, which is controlled by its own thermostat.
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 and air sealed). Each of the zones has its own thermostat, so you only need to condition occupied spaces. This will save energy and money.
Ductless mini-split systems are easier to install than some 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. Most manufacturers of this type of system can provide a variety of lengths of connecting conduits, and, 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 house, but locate the compressor in a more advantageous or inconspicuous place on the outside of the building.
Mini splits have no ducts, so they avoid the energy losses associated with the 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 interior design flexibility. 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 are about seven inches deep and have 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 help keep your home safer, because there is only a small hole in the wall. Through-the-wall and window-mounted room air conditioners can provide easy access for intruders.
Ductless Mini Splits
The popularity of ductless air conditioners continues to grow as consumers search for alternatives to window units and conventional central air conditioning systems. Sometimes referred to as “mini splits,” ductless technology provides a cost effective alternative for applications where the use of ducted A/C equipment would be impractical.
The Basics of Ductless Air Conditioning
A ductless air conditioner operates in essentially the same manner as its ducted counterpart. The heart of every A/C system includes a compressor that applies force to low pressure refrigerant and transforms it into a high pressure gas. The condenser and fan work together to dissipate the accumulated heat, and the refrigerant emerges as a high pressure liquid. At the evaporator coil, the liquid extracts heat from the indoor air and the resulting low pressure gas is pumped back into the compressor to complete the cycle.
Like a conventional split system, ductless air conditioners include an outdoor condensing unit to help minimize interior noise. While central air conditioners employ a single air handler, blower, and evaporator coil, mini split systems house all three components together in separate indoor units that are strategically placed throughout the building. Stylish enclosures are hung on interior walls or placed in the ceiling, which completely eliminates the need for ductwork in the air distribution design.
Ductless split systems are available in a variety of configurations through the utilization of different components. When assembling a complete system, it is important to understand the various equipment options as identified in the table below.
Applications of Ductless Split Systems
Ductless split systems are extremely versatile and can be used to provide cool comfort for a variety of different applications.
In addition to replacing central air conditioning equipment, ductless systems are often a suitable alternative to room air conditioners. Since the evaporator and condenser are separate components, mini splits are much quieter and more energy-efficient than room air conditioners. Security is also enhanced since ductless components do not need to be positioned in an open window.
Advantages of Ductless Technology
Ductless air conditioners have many advantages when compared to traditional central air conditioning systems. The growing popularity of the technology is driven by a variety of factors.
Conventional air conditioning systems utilize a network of interconnected duct runs that are used to deliver conditioned air to the various sub-domains within the home or building. Constructed of metal or flexible plastic, ductwork is a relatively inefficient distribution method. Connections are prone to leakage, and flexible duct can sag over time. The loss of efficiency from a poorly designed or improperly installed air distribution system can account for as much as 30 percent of total system energy consumption.
In contrast, point-of-use air handlers deliver conditioned air directly into the room without passing through thermally inefficient ductwork. By positioning the air handler directly at the delivery point, ductless systems increase efficiency by eliminating friction loss, leakage, and design deficiencies. Additionally, the placement of individual fan coil units throughout the building creates independent cooling zones that can be adjusted through individual thermostats to meet the lifestyle demands of the occupants. Zone cooling allows for higher temperature settings in unoccupied rooms, which can result in substantial energy savings.
Although the cost of ductless air conditioning equipment may be higher when compared to a conventional system or a room air conditioner, ductless split systems are very cost effective over the life of the equipment. In new construction, eliminating ductwork and the air distribution system can result in substantial cost savings. Ductwork often causes unnecessary building design modifications that are eliminated by using ductless equipment.
Room air conditioners are generally noisy and inefficient. Ductless split systems provide quiet comfort, enhanced cooling options, and superior energy efficiency ratings that can result in significant savings in annual utility costs.
Over time, dirt and debris accumulates in the interior of an air distribution system. When moisture is added through condensation, biological agents have the nutrients they need to propagate. Mold and fungi can degrade indoor air quality and aggravate allergies, asthma, and other respiratory problems. Window units are almost impossible to completely seal, which allows outdoor contaminants to enter the livable area in a home or office.
The evaporator coil in a ductless system is accessible and easy to clean. The absence of ductwork deprives harmful organisms of the environment they need to flourish. Eliminating the dirt and debris that accumulates in ductwork can help keep a home cleaner, healthier, and smelling fresh.
When a central air conditioner malfunctions, the entire structure is affected, and the indoor temperature will remain uncomfortable until the unit is repaired. In areas where summer heat is extreme, this can create health risks for the elderly and small children. Since ductless systems often employ multiple condensing units in different zones, occupants can move to the areas of the home or office that are still air conditioned.
Ductless split systems are unique in that the most recent manufactured products include inverter technology. When a room has a light cooling load, a variable speed motor allows the compressor to run more slowly, which reduces energy costs. When the room has a higher cooling demand, the motor signals the compressor to run at a higher speed. In addition to saving energy, the unit is far more responsive and quick to provide a measured amount of conditioned air into the living space.
Understanding SEER Ratings
Every air conditioning unit has an associated Seasonal Energy Efficiency Rating (SEER) that is used to measure its performance relative to other brands and models of equipment. These ratings were developed and adopted by the U.S. government to provide consumers with a meaningful way to compare the energy usage of the equipment produced by different manufacturers. SEER ratings are percentage based, so a 16 SEER system is about 37 percent more efficient than a 10 SEER system. In practical terms, for every $100 spent on fuel costs for a 10 SEER air conditioner, a 16 SEER system would cost only $63.