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If you’re exploring just how well a Mitsubishi Electric Cooling & Heating ductless air conditioner or heater can serve your space, there are some terms you need to know. Here are the most common ones you’ll come across as you research this highly efficient comfort technology.

Air Conditioner

An air conditioner is a device that operates according to the principles of the refrigeration cycle to regulate the temperature and humidity inside a building. Air conditioners are used in warm and hot climates to cool and dehumidify the indoor environment


A British Thermal Unit (BTU) is a standard measurement used to calculate the total amount of thermal energy generated by a heating or cooling unit. In specific terms, one BTU is equivalent to the amount of heat required to raise one pound of water one degree Fahrenheit.

Ductless Condensing Unit

In a ductless split system, the condensing unit houses the compressor, condensing coil and fan. Its primary function is to exhaust accumulated heat energy from the indoor environment during the refrigeration cycle. Heat pump condensing units have the capability to extract heat from outdoors and transfer it indoors when in the heating mode.

Ductless Mini-Split

A ductless mini-split system is a self-contained heat pump or air conditioner that does not require a duct system to function properly. The air handler is connected to the condensing unit by electrical wiring and copper tubing that passes through a small hole in the exterior of the building. Essentially, a mini-split is a heating and air conditioning device that can be used for a single room or multiple zones.

Ductless Indoor Air Handler

The indoor air handler is a fan coil unit that incorporates a blower, evaporator coil, circuit board and controls into a single enclosure. The indoor unit is available as a wall-mounted cabinet or a ceiling cassette. Most ductless systems include a remote control to modify the temperature, fan speed and louver setting.

Ductless Heat Pump

A ductless heat pump incorporates reversing valve technology to accommodate the flow of refrigerant in either direction. This allows a heat pump to serve as both an air conditioning and heating appliance. Ductless heat pumps are best suited for relatively mild winter climates where the outdoor temperature rarely approaches freezing.


The Heating Seasonal Performance Factor (HSPF) is a rating system developed by the Air Conditioning, Heating, and Refrigeration Institute (AHRI) to provide consumers with an effective and simple way to compare the relative efficiency of heat pumps when in the heating mode. The HSPF rating number is a reflection of the quantity of thermal heat energy that is generated relative to the amount of electricity consumed in the heating process. A higher HSPF number indicates a more energy efficient unit.

Inverter Driven Compressors

Ductless air conditioners and heat pumps equipped with inverter technology can regulate the operation of the compressor to provide exceptional efficiencies. The system senses variations in the temperature and adjusts capacity output to precisely match the prevailing load. Mitsubishi offers a variety of inverter equipped heat pumps and air conditioners that provide efficiency ratings up to 26 SEER.

Multi-Zone Ductless Systems

A multi-zone ductless split system is characterized by a single condensing unit that serves multiple indoor air handlers. The condenser integrates several compressor circuits that are individually dedicated to each fan coil. Every indoor unit has its own remote control, so the temperature in each room can be adjusted to suit the comfort expectations of the occupants.


The Seasonal Energy Efficiency Ratio is a measurement of the efficiency of an air conditioner or heat pump while in the cooling mode. Determining the percentage difference in efficiency between two units can be accomplished by dividing the lower SEER rating by the higher SEER rating and using the reciprocal result.

Split Ductless System

This type of system contains both an indoor and outdoor unit. The two are connected by refrigerant lines and the system requires ducts to carry conditioned air.


This is made up of one or more rooms in the same building with each zoning having its own temperature control independent of other zone(s).

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