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Ductless Mini Splits - How They Work and Why They're Superior to Window Units

Ductless mini splits deliver a plethora of advantages to homeowners seeking an efficient and simple means to provide primary or supplemental heating and cooling for remodeled rooms, new additions and more. If you're remodeling your home or just seeking practical space heating and cooling, explore the many benefits of ductless systems, and you'll understand why ductless systems are earning a reputation as the best heating and cooling solutions for home improvement projects.

What Are Ductless Mini Splits?

Developed by Mitsubishi Electric more than 30 years ago, ductless mini splits are heat pumps and air conditioners with redesigned sleek components, which allow for more versatile, practical and space-saving installation options than their ducted forced-air counterparts.

Ductless systems heat and cool by the same refrigeration principles as conventional heat pumps and air conditioners, but their highly-efficient and compact components are housed in three separate units, which include an outside cabinet, a thin conduit and one or more indoor air handlers with no obtrusive ducts.

Ductless Mini Splits or Window Units

If your home improvement project involves finding a solution for supplemental heating and cooling for existing rooms and spaces, remodeled rooms and/or new additions, perhaps a window A/C or heat pump has crossed your mind. Window-mounted units often cost less than the expense of extending air ducts into new spaces, and, though it's not the simplest do-it-yourself project, window units may be installed by the homeowner.

With versatile and unobtrusive installation options, high-efficiency operation and smart features designed to enhance home comfort and indoor air quality (IAQ), ductless mini splits unpretentiously offer brains, beauty and healthy IAQ while offering energy efficiency.

The following features highlight the points which put ductless systems far ahead of window-mounted units:

  • Aesthetics: The only components of a ductless system that are visible inside the home are the sleek indoor air handlers, which house the evaporator coil, IAQ components and other essential parts. The air handlers may be installed flush in a ceiling panel of a suspended ceiling or mounted high on walls, any ceiling surface or mounted on the floor.

    The inconspicuous location of the air handlers is a stark contrast to window-mounted units, which block sunlight and view and are rather unattractive in many installations. The thin conduit is routed inside walls and other inconspicuous areas, and it may extend to well over 100 feet, which allows for versatile location options of the outside cabinet. The compact outside cabinet may be nestled and hidden among softscapes or installed anywhere you deem appropriate for best aesthetics, if that's your objective.
  • Noise: With ductless mini splits, you don't have to turn up the TV volume to hear your favorite show or raise your voice to hold a conversation in order to heat and cool your home. Noise is a factor which affects the home-comfort experience and rest and relaxation of household occupants. It can be challenging to sleep the night through with a window unit whirring at more than double the decibels of ductless mini splits, and those are the "quiet" window units. The component guilty of making all that stop-and-start whirring noise is the compressor, which, with a window unit, is practically located inside the living space. 

    Moreover, many window units permit outside noise to infiltrate the home's shell through the unit itself. With the compressor located outside the home, many models of ductless mini splits produce no more noise than that of a human whisper, breathing filtered heated and cooled air to exactly the spaces you need it.
  • Energy efficiency: Heating and cooling efficiency for ductless mini splits is displayed as heating seasonal performance factor (HSPF) and seasonal energy efficiency ratio (SEER), and ductless systems boast impressive numbers, easily surpassing the energy efficiency of window units and conventional heat pumps and air conditioners.

    Some of the advanced technologies and performance-driven features which deliver high efficiency ratings are inverter technology and scroll compressors, which are variable-speed compressors that maximize refrigerant efficiency for extracting and releasing heat. Multiple sensors monitor and regulate heat-exchanger coil temperatures for precise temperature control in the living spaces. Additional sensors scan the room, top to bottom, to detect uneven room temperatures and adjust heating or cooling output in real time. A multi-speed fan may be adjusted for energy savings and home comfort.

    If you're installing more than one air handler, each air handler heats and cools as a separate zone, leveraging more energy savings by using heating and cooling zones as needed. All of these advanced features are engineered to last with fewer repairs than conventional components, which, in addition to energy savings, is great news for your pocketbook.
  • Indoor air quality (IAQ): The indoor air handlers contain optional IAQ components which greatly enhance the quality and healthfulness of the air inside your home. With ductless mini splits, the air inside the room or area which is being heated or cooled is continuously cycled through the air filtration system. It's as if you have a portable air cleaner in each room containing an air handler. You may select one or more types of filters, including electrostatic filters which literally attract airborne contaminants, carbon-activated filters which neutralize odors and anti-bacterial filters which help protect the living spaces and household occupants from harmful germs.

    The IAQ components of ductless systems are sure to be an attractive option for occupants suffering from respiratory ailments, such as allergies and asthma. Moreover, the air filtration system keeps the evaporator coil and other essential parts clean of debris which may otherwise accumulate and compromise performance and efficiency. And, with no air ducts involved with ductless mini splits, there's no possibility for dust and debris accumulation and subsequent discharge from dirty air ducts.
  • Safety: It doesn't escape anyone's attention that window-mounted units are a potential safety and security issue for the occupants. It doesn't take a rocket scientist to pull a window unit from its mounts, and it may even be easier than other access points to the home. Ductless mini splits present no risks to safety and security. The only opening or protrusion into the home is a small hole, perhaps 3 to 4 inches, which the conduit extends through to connect the outside cabinet to the indoor air handlers.


How Ductless Mini Splits Work

Using the same refrigeration principles as conventional heat pumps and air conditioners, the refrigerant circulating inside the heat-exchange coils extracts and releases heat from and to the air from one location to another, depending on whether the ductless system is in heating or cooling mode. This principle of heat exchange makes ductless mini splits well capable of delivering in excess of 400-percent efficiency of heat energy delivered per electricity consumed.

These are the primary components of ductless mini splits and how they function together to deliver efficient heating and cooling:

Cooling Mode


  • Temperature sensors continuously scan the room for temperature readings and to detect temperature variances in the form of hot and cold spots.
  • The compressor pumps refrigerant through tubing which is housed in the long, thin conduit.
  • The refrigerant flows into the evaporator coil housed inside the indoor air handler.
  • The air handler pulls air through the IAQ components and across the evaporator coil.
  • The refrigerant vaporizes and extracts heat from the air.
  • During this heat extraction process, moisture in the air condenses on to the surface of the evaporator and then drains through the condensate line, which is housed in the conduit, to exit the home.
  • The air handler recirculates the air, which is now cool, to the living space. (The air handler may be multi-speed with oscillating features for optimal comfort and room coverage.)
  • The refrigerant flows to the compressor in preparation for heat release.
  • Refrigerant flows into the outside heat-exchange coil (condenser), and the refrigerant becomes extremely hot as it is condensed.
  • A blower pulls air across the condenser which instigates the refrigerant to release heat to the outside air.

This refrigerant-cycling process of heat extraction from living-space air and heat release to outside air continues for long periods of time, which helps the ductless system maintain indoor temperature to within one degree of the thermostat setting for maximum comfort, humidity management and great energy efficiency. 

If you're installing a ductless mini split heat pump, a reversing valve allows the refrigerant cycle to be reversed, which causes the refrigerant to extract heat from outside air and release the heat inside the home for comfortable and efficient heating.

More Benefits of Mitsubishi Ductless Mini Splits

With the advanced technologies of Mitsubishi ductless mini splits, comfortable cooling capacity is achieved on even the hottest and most humid Virginia summer days. Moreover, Mitsubishi ductless heat pumps are for all seasons. They're fully capable of heating one or more rooms in your home when outside temperatures dip into single digits. No window unit can come close to this kind of performance.
If you're considering heating and cooling options for your home improvement project, contact a Mitsubishi Electric Contractor near your Virginia home for the best service and installation from the company that created ductless mini splits.

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