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How Does Ductless Air Conditioning Work?

The physical realities of new construction or remodeling projects often limit the amount of space available for building infrastructure systems. Building plans and expectations sometimes have to be made so that all necessary systems can be included and installed to work at the required level. Heating and cooling systems are of particular concern when working with lesser amounts of space or restricted renovation options in home-based projects. HVAC systems commonly require large amounts of available room for the installation of equipment and ductwork.

For homeowners and construction professionals who need a space-saving alternative to traditional ducted HVAC equipment, ductless mini split heat pumps offer a practical and fully functional solution. How does ductless air conditioning work? The following brief guide will introduce you to ductless air conditioning.

Why Use a Ductless Air Conditioning System?
Ductless air conditioning systems are also known as ductless mini split systems, or mini splits. Ductless HVAC systems are usually more than air conditioners--they are full-featured heat pumps that provide both heating and cooling. They are particularly useful in construction and remodeling projects where:

  • Available space for installing a large, bulky ductwork system is limited or not available, such as in many types of urban construction projects or historical renovations.
  • A ducted infrastructure does not already exist, or the existing ductwork is inadequate.
  • Structural changes to accommodate a duct network are not feasible because of the building's historical significance, owner preferences or other factors.

How Does Ductless Air Conditioning Work?
Ductless mini splits consist of sets of both indoor and outdoor components. The outdoor cabinet, usually installed near an external wall, contains the main system components, such as the condenser, compressor and evaporator. The indoor components consist of up to eight smaller air-handling units that distribute the warm or cool air produced by the equipment. The indoor units are connected to the outside unit via a conduit in the wall. The conduit contains power cables, refrigerant lines and drainage pipes.

Ductless air conditioning systems work the same as standard heat pumps. They use the principle of capturing heat and moving it to a different place. In the summer, the system moves heat out of your indoor spaces, which generates cooling. In the winter, the unit brings heat in from outdoor air or other sources, providing indoor heating.

Heat capture and release is accomplished using the liquid refrigerant that circulates through the indoor and outdoor components. In the evaporator, the refrigerant changes state from liquid to gas. As it does so, the refrigerant absorbs heat. The hot gas circulates through the system and is returned to liquid form in the condenser. As the gaseous refrigerant returns to liquid form, it releases the heat it contains. The refrigerant flows back through the system for the cycle to begin again.

As the heat is captured and released, the indoor air handling units distributed heated or cooled air to the inside of your home. Each indoor unit has an independent thermostat, which offers complete control over the amount of heating or cooling it provides. The small size and flexibility of the indoor units mean they can be placed almost anywhere within your home, limited only by the length of the pipes and cables that connect them to the outdoor units.

Advantages of a Ductless Air Conditioning
As a popular alternative to traditional HVAC equipment and heat pump systems, ductless mini splits offer many attractive and practical advantages. Though ductless HVAC systems are usually smaller than standard heat pumps, they are just as efficient and effective as their larger-sized counterparts. Heat pumps are well known for being highly energy efficient and economical to operate, producing substantial amounts of heating and cooling at the lowest possible cost. Ductless mini splits offer the same functional advantages, just in a smaller overall package.

  • Ease of installation: Since ductless systems require no ductwork, they are easier to install than larger heat pumps. The outdoor unit is usually about the same size as that found in a ducted heat pump system. However, the indoor air handlers are small enough to place almost anywhere. They are commonly installed either on the wall, the ceiling or the floor. Wall-mounted units often look like small fans or rectangular radiators, while floor mounted units tend to resemble a square radiator.
  • High efficiency: Just like a standard head pump, ductless mini splits are highly efficient. They must carry a minimum Seasonal Energy Efficiency Ratio (SEER) of 13, the same as central air conditioners. Higher efficiency systems will have higher SEER numbers. In general, mini split systems can reduce monthly heating and cooling costs by 30 percent or more.
  • Better cooling and heating: The quality of heating and cooling is often better when using a ductless system. Since there is no ductwork, there is no chance of leaks in the air distribution system, which causes the loss of conditioned air. More heated or cooled air reaches the inside of your home, improving indoor comfort levels. The lack of ducts also means there is less chance for particulates or other contaminants to enter your air distribution system and be carried into your living spaces.
  • Independent operation: The individual thermostats on the air-handling units mean that they can be operated independently of each other. This is useful in creating a zoned heating or cooling system that focuses conditioning in certain rooms or areas of your home. Room occupants can choose their preferred temperature settings without interfering with heating or cooling in nearby areas. If you have an area of your home that needs more heating or cooling than another space, you can add an additional indoor unit to boost the conditioning there. If you have an area that doesn't need heating or cooling at all, you can choose to not put an indoor unit there, which means you'll not be wasting money and energy conditioning an unused space.
  • Increased room design options: Since the indoor units of ductless systems can be placed in various locations, they offer homeowners better interior design options. The indoor units can be incorporated into any designs or, if desired, can be placed out of sight where they will not interfere with the placement of furniture, rugs or other room design elements.

Maintenance Needs
Like any other heat pump system, your ductless air conditioning equipment will need regular preventive maintenance to keep it working properly. Lack of maintenance is a prime cause of system malfunctions and breakdowns. A poorly maintained ductless system will be more expensive to operate because it will be less efficient, and at the same time the quality of heating and cooling it produces will be reduced.

Preventive maintenance should be performed at least annually. Since ductless systems are often used in both winter and summer, twice-yearly maintenance and service inspections, one at the beginning of each season, may be a better option. Contact your local trusted HVAC contractor to schedule a service appointment or to establish a service contract.

To keep your ductless HVAC system working at its best, either you or your HVAC professional should perform the following maintenance tasks:

  • Change filters regularly: Air filters are required for removing particulates and contaminants from your indoor air. They are also necessary for providing proper airflow for system function. Dirty filters are a primary cause of HVAC system malfunctions, damage, and breakdowns. Filters should be checked at least monthly and changed if they are dirty. If your indoor air tends to contain more contaminants than normal, it may be necessary to check and change filters more often.
  • Clean the outdoor unit: Remove any accumulations of dirt, grass, leaves, sticks or other material that could block airflow or interfere with the unit's function. Keep the coils free of accumulated material that could affect heat transfer and system function. Trim tree limbs, shrubs, grass and other vegetation to allow two feet of clearance on all sides of the outdoor unit and five feet of clear space above it. A light coat of automobile wax on the outdoor cabinet will help protect it from sunlight and the elements.
  • Maintain recommended refrigerant levels: The manufacturer will indicate the amount of refrigerant that is necessary for proper system function. Too much or too little refrigerant will affect system performance. Check refrigerant lines for leaks and, if any are found, have them repaired immediately. Consider installing locks or other security features to prevent refrigerant theft.
  • Test and adjust system controls: Make sure all controls are working properly. Repair or replace any controls that need it.
  • Check the drains: Keep the drains clear and free of blockages. Apply algaecide to prevent algae growth in the drain system or clean the drain pan with a bleach solution, if necessary. Ensure no standing water is in the drain pans and that water can flow freely down the drain pipes.

Mitsubishi ductless air conditioning systems provide top-quality home comfort with all the benefits and conveniences of a ductless cooling system. For more information on ductless air conditioning, contact your local Mitsubishi Electric contractor.


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