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Frequently Asked Questions

Whether customers are buying a new HVAC system or replacing an existing system, they often have questions about the different products on the market. This helpful FAQ sheet can serve as a guide to some of your most commonly asked questions. By reading these air conditioner FAQs, you can acquire more information about ductless systems and have a better understanding of how they operate. You can also learn about maintenance, energy efficiency and the different types of ductless systems.

What is a ductless air conditioning system?

A ductless air conditioning system is similar to a central air conditioner, but it does not require ducts for air movement. Ductless systems are very energy efficient and are typically used to heat and cool different zones in the same building. The system consists of an outdoor compressor and one or more indoor evaporator units. The outdoor and indoor units are joined by a thin conduit, and this passes through your wall. The conduit contains the refrigerant, suction tubes, condensate drain and power cable.

The compressor does not need to be installed close to the indoor units. In fact, your HVAC contractor can place the compressor up to 100 feet away from the evaporators. When installing your system, the contractor can adjust the length of the conduits to fit with your home's design. The indoor units are relatively thin and are typically mounted on or near the ceiling. However, it's also possible to place the evaporator on the floor. A ductless system that has multiple indoor units is known as a ductless mini-split system. In this type of system, each evaporator unit is controlled independently, so each zone can maintain its desired temperature.

Do I need to keep my existing HVAC system?

It's not necessary to keep your existing system, but some customers decide to use their old systems for additional temperature control. A ductless system is designed to be the primary source of cooling for your home, and ductless heat pumps provide both heating and cooling. However, because ductless systems are primarily focused on certain zones, you may want to have additional heating or cooling in some areas of your home. During periods of extreme heat or cold, your existing system may be able to provide additional temperature control for the areas that need it. A ductless system is designed to work well with radiant panels, heat pumps and other types of heating and cooling units, so you can enjoy a comfortable indoor climate all year.

How do ductless HVAC systems operate?

A ductless unit operates in the same way as a traditional heat pump, but there is no ductwork involved. A ductless system contains reversible mechanics that provide both heating and cooling for specific zones within the same building. The outdoor unit houses a variable speed compressor, a condensing coil, a fan and an expansion valve. The indoor units house the evaporators and fans to help distribute the air into the rooms. The outdoor unit is connected to the indoor units by narrow conduits. During the cooler months, the heat pump operates on a heating cycle, and during the warmer months, the system operates on a cooling cycle.

During the heating cycle:

  • The compressor pulls ambient air from the outside and passes it over the condensing coils.
  • The internal fan cools the coils and prevents the system from becoming overheated.
  • The heated air passes through the conduit into the evaporators and is distributed to zones within the building.

During the cooling cycle:

  • The system extracts warm air from the inside of your home and carries it to the outdoor unit.
  • As the air passes over the evaporator coils, the refrigerant cools the air.
  • The cooled air is then distributed to each zone by the unit's fan.
  • The evaporator also dehumidifies the rooms and allows for a more pleasant indoor environment. Because the humidity is gone, the thermostat can be set higher, which saves a great deal of energy.

Each system features inverter technology, which helps to conserve energy. Instead of continuously rotating on and off, variable speed compressors help maintain the desired temperature for longer periods of time. This technology also allows for more uniform temperatures in each zone and provides a more comfortable home environment. Also, each evaporator is operated by a separate control and can be programmed to an exact temperature.

How is a ductless system controlled?

A ductless system can be operated by either a remote control or a wall-mounted control, and your choice depends largely on personal preference. With a remote control, you can operate the unit from anywhere inside the zone, so if you are sitting down, you can still adjust the temperature. On the other hand, a wall-mounted device prevents children from inadvertently adjusting the temperature and prevents you from misplacing the remote. A ductless system allows you to set the exact temperature, so you can maintain a more comfortable indoor climate. You can also use your control to switch between cooling and heating modes and day and night settings. These features allow you to conserve energy and still remain comfortable. In addition, each evaporator in a mini-split system has its own controls and thermostat.

Can a ductless system be installed in any type of building?

A ductless system can be installed in many different places. You can speak with your HVAC contractor to find out if this type of system is the right fit for your home or office building. Many older buildings do not have installed ductwork, and it may be inconvenient to have the ductwork installed. Also, ductwork requires enough space to house the ducts, and not all buildings have this kind of room. Here are some scenarios where a ductless system would be an ideal fit.

  • Existing Structures without Ductwork – If a building does not have ductwork installed, it may be difficult or impossible to retrofit the building with ducts.
  • New Room Additions – When a new room is added a home, installing a ductless system is a cost-effective solution to controlling the climate in the new room. Extending the existing ductwork is expensive, and often, fans, space heaters and window air conditioners don't do an adequate job of heating and cooling the room. A ductless system is also ideal when you are converting a garage, basement or attic into a livable space.
  • Upgrading Older Systems – Some older homes and buildings have air conditioning and heating systems that are extremely inefficient and outdated. A ductless system is an energy-saving alternative to an outdated window unit, space heater, baseboard heater or stove.
  • New Homes – If you are building a new home, it may be more cost effective to install a ductless system instead of adding ductwork. Depending on how large your home is, you can install one system or multiple ductless systems for controlling various zones within your home. If you are building a two-story home, you may find that a ductless system works better than a forced-air system for cooling and heating the second story.
  • Supplementing an Existing System – Even if you have an existing energy-efficient HVAC system, you may find that not every area in the home feels comfortable. Some rooms can benefit from extra heating or cooling, and a ductless system can provide the extra climate control you are looking for. You can choose a ductless system for the main zone or smaller rooms.
  • Seasonal Homes – If you have a summer or winter home, you might find it more cost effective to use a ductless system. When the home is in use, the ductless system can provide efficient climate control, but you won't have to worry about maintenance when the home is not occupied.

Is a ductless system energy efficient?

Ductless systems are renowned for being extremely energy efficient and for having low operating costs. Ductless air conditioners and heat pumps enjoy high SEER ratings and also high HSPF ratings for heating. The typical SEER rating on a ductless unit is 22, and the HSPF rating is often higher than 10. These are significantly higher than the minimum energy-efficiency requirements in all 50 states. Ductless systems typically consume up to 50 percent less energy than ducted systems.

By featuring variable speed compressors, ductless designs and zonal control, these systems are able to save energy and often contribute to lower utility bills.

  • Ducts that leak air or are too small often account for up to 30 percent of the system's energy loss.
  • A zonal system heats and cools the rooms that require the most climate control.
  • By using a variable speed compressor, a ductless system can conserve energy by adjusting the speed to maintain a constant temperature.

Where did ductless systems originate?

The technology behind ductless air conditioning originated in Asia and was concentrated in Japan. Asian building design made it difficult to install ductwork, and most buildings utilized window air conditioners. However, these units took up needed space and were often loud, so by the 1970s, engineers were looking for ways to improve this design. Ductless systems were ideal for controlling the climate, and they used less space and were considerably quieter than window units. Ductless units provided an ideal solution for controlling the indoor air climate in places where ducted systems were not possible.

Eventually, the new technology and innovation spread to North America, Europe and other areas of the world. As time went on, ductless systems began to offer additional benefits and new features. The new designs included longer conduits, larger system capacities, programmable controls and wider temperature ranges. Today, ductless systems are common throughout Europe and Asia, and many commercial buildings in the United States have been using these systems for more than 20 years.

How much do ductless systems typically cost?

Although there are various factors that can affect the cost of a ductless system, the average price of a single indoor unit ranges from $3,000 to $5,000. The cost can increase if more units are installed to cover multiple zones. In addition, the price often varies between models, manufacturers and the system's size. You also need to factor in the added costs for installation, and this is determined by the contractor you hire. Even though the initial costs may be high, the system's energy efficiency and your reduced utility bills will end up saving you money in the long run.

Are incentives or rebates available for ductless systems?

Both the federal and state governments offer incentives for purchasing and installing energy-efficient equipment. In most cases, you can also receive incentives from the manufacturer. Typical incentives include tax credits and cash rebates. Additionally, you may be able to qualify for incentives from your local utility company. Here are some things to look for.

  • Manufacturer Rebates – When you purchase your ductless system, check to see if there are any incentives offered by the company that manufactures the equipment. Not all companies offer incentives, but it can be worth your while to find out.
  • Federal Tax Credits – You may be eligible for a federal tax credit after you purchase and install a qualifying energy-efficient ductless system. Some credits are only for business owners, but others are offered to homeowners. Not all ductless systems are eligible, but you can check with your accountant or visit the Energy Star website.
  • State Tax Credits – For information on state tax credits and other incentives, you can check your individual state's tax rules. One helpful resource is the Database of State Incentives for Renewables and Efficiency. Here, you can locate more information on tax credits for ductless systems.
  • Cash Rebates – Many utility companies offer their customers cash rebates for purchasing and installing a ductless system. You may qualify if you buy a new system or upgrade your existing system, and you may be able to qualify for special financing. You can contact your local utility company for additional information.

What is the average lifespan of a ductless heating and cooling system?

With regular maintenance and upkeep, most ductless systems last for over 20 years. Ductless systems are extremely durable and are manufactured to provide superior climate control for a long time. In most cases, recalls are very rare. In fact, customers who purchased ductless systems in the 1980s are still enjoying the benefits of their energy-efficient units.

What type of maintenance does a ductless system require?

Like all HVAC systems, ductless units require regular maintenance to keep them running smoothly, but the maintenance is minimal. Each month, you should clean or replace the air filter to ensure that your home is receiving clean air. Each quarter, the evaporator and condenser coils should be cleaned, and this can usually be accomplished by wiping them with a damp rag. You can also have the maintenance performed by your local contractor. By keeping your ductless system properly maintained, you can prolong its lifespan and ensure optimal performance.

Ductless systems come in various sizes. How can I determine the correct size for my home?

Every home is different, and ductless systems come in various sizes to handle the heating and cooling requirements of various homes and businesses. The size of a ductless system is determined by BTU capacity ratings, and both indoor and outdoor units have different capacities. In a home with a multi-zone system, the outdoor compressor unit's load is required to meet the combined loads of all of the indoor units. Typically, the size of the system is determined by the square footage of your home and the required volume for each zone. The capacities of most indoor units can range from 9,000 to 30,000 BTU. In larger homes, it's common to find more than one ductless system. However, the best way to determine the correct size for your home is to speak with your Mitsubishi Electric Diamond Contractor.