Special Offers
Glossary of Terms
Ductless HVAC Glossary of Terms

Air Conditioner

A system for controlling the temperature and humidity of the air in a building. Controlling the temperature is being able to heat and cool. Not only cool.

Air Handler

The air handler is an important part of your air conditioning equipment. Its job is to effectively circulate conditioned air throughout your home.

BTU (BTU stands for British Thermal Unit).

One British Thermal Unit (BTU) represents the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit. The heat extracted from your home by an air conditioner is measured in BTUs.


Some systems are measured in British Thermal Units per Hour (BTUh). The heat extracted from your home by an air conditioner is measured in BTUs, while cooling and heating capacities are referred to in British Thermal Units per hour. For reference, 12,000 BTUh equals one ton of cooling.


The coil, also known as an evaporator coil or an indoor coil, is the unsung hero of any home heating or cooling system. Its job, heat transfer, is one of the most important factors in achieving heating and cooling efficiencies that keep your home comfortable all year long.


A compressor is a device that increases pressure on a fluid. In an air conditioner or heat pump, the compressor changes the refrigerant from a gaseous state back into to a liquid state.

EER (EER stands for Energy Efficiency Ratio).

Like SEER, the Energy Efficiency Ratio (EER) of a cooling unit is determined by the output cooling divided by the electrical power input. As opposed to SEER which is calculated over a range of outside temperatures, EER is typically determined by a set outside air temperature, a set inside air temperature and a 50% relative humidity. For a comparison point, 11 EER is roughly equivalent to 13 SEER.


ENERGY STAR is a voluntary labeling program developed by the U.S. Department of Energy and the Environmental Protection Agency (EPA) in 1992 to promote awareness of energy-efficient products.

Heat Pump

A heat pump is a piece of equipment that moves heat from one area to another via a refrigerant. In cooling mode, heat is removed from indoor air and transferred outside; in heating mode, the refrigerant is reversed and the heat is removed from the outdoor air and transferred indoors.

HSPF (HSPF stands for Heating Seasonal Performance Factor).

HSPF stands for heating seasonal performance factor. The HSPF denotes the efficiency of a heat pump; the higher the HSPF, the greater the heating efficiency. It is calculated as a ratio between the heat production over a heating season and the watt-hours of electricity used.


HVAC is an acronym for heating, ventilation and air conditioning. It refers to the different systems, machines and technologies used in indoor settings such as homes, offices and hallways, and transportation systems that need environmental regulation to improve comfort.

Indoor Unit

The indoor unit is the part of an air conditioning system that sits inside the room or structure and distributes heated and cooled air to the indoor space. It contains a fan, filters, motor, coil and an air filtering device; the air filtering device is often called the air handler.

Inverter Technology

The Inverter technology (DC) is the latest evolution of technology concerning the electro motors of the compressors. An Inverter is used to control the speed of the compressor motor, so as to continuously regulate the temperature. The DC Inverter units have a variable-frequency drive that comprises an adjustable electrical inverter to control the speed of the electromotor, which means the compressor and the cooling / heating output.

Outdoor Unit

The outdoor unit is the part of an air conditioning system or heat pump that sits outside of the room or structure. It serves as a heat exchange point; in summer, it removes the heat from the indoor air and dispels it to the outside. In winter, it removes heat from the outdoor air and delivers it indoors. The outdoor unit contains a compressor, fan and coil.


A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. Ductless Mini Split Heat Pumps uses R-410A, which is environmentally friendly and does not deplete the ozone.

Refrigerant Lines

Refrigerant lines carry the refrigerant between the indoor and outdoor units. They are usually made of copper.

SEER (SEER stands for Seasonal Energy Efficiency Ratio).

The Seasonal Energy Efficiency Ratio (SEER) measures air conditioning and heat pump cooling efficiency, which is calculated by the cooling output for a typical cooling season divided by the total electric energy input during the same time frame. A higher SEER rating means greater energy efficiency.

Split-Ductless System

A split-ductless system is a cooling system where the condenser (outside unit) is separated from the air handler (indoor unit); the two are connected via electrical and refrigerant lines. The air handler delivers conditioned air directly to a room or space.

Split-Zoning System

The same as a split-ducted system. Split-zoning allows each space to be controlled separately.


A zone is a room or space to be heated or cooled. Zoning provides ultimate comfort control because the temperature in each zone is unrelated.