HVAC Terminology

Understanding your air conditioning and heating system means being familiar of all associated air conditioning and heating terms. Below you will find a glossary of HVAC terms that you should know. If you have any questions or we can assist you in any way, please contact Air Repair at 972-625-1400.

Adequate Exposure Diversity (AED) – Adequate Exposure Diversity is a calculation of the total glass load to see if any hourly total exceeds the 12 hr average by more than 20 or 30%.

AFUE – AFUE is an acronym that means Annual Fuel Utilization Efficiency. AFUE reflects how efficiently a gas furnace converts fuel to energy. An AFUE of 90 means that approximately 90 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent escapes as exhaust.

Air Balancing – Air Balancing is the adjusting of an air conditioning system so that the right amount of air is delivered to the right places in your home in order to achieve the proper cooling and heating effect.

Air Cleaner– An air cleaner is a device that removes allergens, pollutants and other undesirable particles from air.

Air Conditioner – An air conditioner is equipment that conditions air by cleaning, cooling,heating, humidifying or dehumidifying it.

Air Filter – An air filter is a device that removes particulate material from the air stream.

Air Handler – The air handler of your cooling and heating system is the portion of your air conditioner or heating system that forces air through your home’s ductwork.

ARI – ARI is an acronym that stands for Air Conditioning and Refrigeration Institute, The ARI is a non-profit, voluntary organization composed of heating, air conditioning and refrigeration manufacturers.

Aspiration – Aspiration is a term means to draw up gas. Air is discharged at a high velocity from our outlets creates a vacuum, and the air is then pulled into the and creates a blend of conditioned air.

Balance Point – The balance point is an outdoor temperature, usually between 30° F and 45° F, at which a heat pump’s output exactly equals the heating needs of the home. If it is below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

Brazing – Brazing is a process that is used to bond materials by melting a filler metal between the components being joined.

Breaker – A breaker is a heat activated electrical device used to open an electrical circuit to protect it from excessive current flow.

BTU – BTU is an acronym that stands for British Thermal Unit (BTU) which is the unit of heat required to raise 1 pound of water by 1 degree Fahrenheit. A BTU is a measure of the heat given off when fuel is combusted. For cooling, it’s a measure of heat extracted from your home. (One BTU equals the amount of heat given off by a wooden kitchen match.

BTUH – BTUH is an acronym that stands for British Thermal Units per Hour.

Capacity– Capacity is the production capability of a piece of cooling or heating equipment. Cooling and heating capcity are normally referred to in BTU’S.

Capillary Tube – A capillary tube is a refrigerant control consisting of a small diameter tube which controls flow by restriction. They are sized by inside diameter and length for each particular application.

Central Air Conditioner – Central air conditioning systems have two parts. An evaporator that removes unwanted heat from the air and transfers it to a refrigerant; and a condenser that removes unwanted heat from the refrigerant and transfers that heat outdoors. The primary component of a condenser is typically the condenser coil, through which the refrigerant flows.

CFM – CFM is an acronym that stands for Cubic Feet per Minute. This measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air is being forced through the system.

Circuit Breaker – A circuit breaker is a device that opens an electric circuit when an overload occurs.

CLF – CLF is an acronym that means Cooling Load Factor

Compressor – The compressor squeezes the molecules of the refrigerant gas together, which increases the pressure and temperature of the refrigerant.

Condensate – Condensate is the moisture that is collected on an evaporator coil.

Condenser Coil – The condenser is the outdoor portion of a split-system air conditioner or heat pump. The condenser will converts the refrigerant from a gas form to a liquid and then carry the refrigerant to the outside. This is also referred to as an Outdoor Coil.

Condensing Unit – The condensing unit is the outdoor component of a cooling system. This includes a compressor and condensing coil that is designed to give off heat. It also changes the vapor gas mixture back to a liquid for return to the system.

Damper – THe damper is a type of “valve” used in duct work that opens or closes to control airflow. Dampers are used in zoning to control the amount of warm or cool air entering certain areas of your home.

Dehumidification – Dehumidification is the reduction of water vapor by cooling the air below the dew point,as well as the removal of water vapor from the air by chemical means.

Delta T – Delta T is a term that indicates a temperature relationship between two temperatures or temperature variation between two points.

Drip Pan – A drip pan is a pan shaped to collect moisture condensing on an evaportator coil in an air conditioning system.

Dry Bulb Temperature – Dry bulb temperature is the temperature read with an ordinary thermometer.

Ductwork – Ductwork are hollow pipes used to transfer air from the Air Handler to the air vents throughout your home. The Ductwork is one of the most important components of your homes’ cooling and heating system.

EER – EER is an acronym that stands for Energy Efficiency Ratings. EER measure the efficiency by which a product uses energy to function. It is calcuated by dividing a product’s BTU output by its wattage.

Electric Heat – Electric heat is the process of converting electrical energy into heat.

Electronic Air Cleaner – An electronic air cleaner is an electronic device that filters out contaminants in indoor air. In addition it also pulls particles that have been magnetized, such as viruses and bacteria.

Evaporator Coil – The evaporator coil is the part of a split-system air conditioner or heat pump that is located indoors and cools and dehumidifies the air by converting liquid refrigerant into a gas. The warmed refrigerant is then carried through a tube to the outdoor unit or condenser coil.

Fan Coil Unit – In the fan coil unit the fan distributes air through the plenum; the coils cool (or heat and cool) the air, depending on individual needs and system configuration.

Geothermal Heat Pump – A geothermal heat pump is a heat pump that uses the earth or water in the earth for its heat sources and sinks.

Heat – Heat is a form of energy that acts on substances to raise their temperature.

Heat Gain – Heat Gain is the transfer of heat from outside to inside by means of conduction, convection and radiation through all surfaces of a house.

Heat Pump – A heat pump is a product that works like an air conditioner in cooling mode however, in heating mode, the refrigerant flow is reversed and heat is extrated from the outside air too heat your home.

Humidifier – A humidifier is a device that adds moisture to dry indoor air during wintertime and in hot dry climates.

HVAC – HVAC is an acronym that stands for Heating, Ventilation and Air Conditioning (HVAC).

IAQ – IAQ is an acronym for Indoor Air Quality that refers to the cleanliness and health of the air in a home.

Indoor/Outdoor System – Indoor/Outdoor System refers to a comfort system consisting of components in two locations. Common examples include an outside unit, such as an condensing unit, and an indoor unit such as an fan coil unit.

Infiltration – Infiltration is air that leaks into a structure through cracks, windows, doors or other openings due to less pressure inside the structure than outside the structure.

Latent Heat – Latent heat is heat that when added or removed, causes a change in state – but no change in temperature.

Liquid Line – The liquid line is a tube used to convey the liquid refrigerant from the condenser outlet to the refrigerant control device of the evaporator.

Load Estimate – A load estimate is a series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the cooling and heating capacity needed by your furnace, heat pump or air conditioner.

Manometer – A manometer is an instrument used for measuring the pressure of liquids and gases.

Matched System – A matched system is an air conditioner or heat pump system composed of equipment that has been certified by ARI to work together to deliver the specified cooling and heating capacity at the stated efficiency rating.

Nitrogen – An inert gas that is often used to ‘sweep’ a refrigeration system to help ensure that all refrigerant and contaminants have been removed.

Open-loop heat pump – An open-loop heat pump is a heat pump system that uses water in the earth.

Outdoor Coil/Condensing unit – The outdoor coil is the part of a refrigeration system where the compression and condensation of refrigerant is accomplished. Sometimes referred to as the ‘high side’.

Outlet – An “outlet” is how the conditioned air enters the living space. These 5″ diameter outlets can be placed in the ceiling, wall, or floor.

Plenum – The Plenum carries air to the different ducts to be distributed throughout the house.

Programmable Thermostat – A programmable thermostat is a type of thermostat that allows the user to program a pre-set schedule of times to turn on your air conditioning system.

R-22 Refrigerant – R-22 is a HCFC refrigerant with low ozone depletion potential. It has long been used in the air-conditioning markets but will cease in 2015 as per the Montreal Protocol.

R-410A Refrigerant – R-410A is an HFC refrigerant that has no undesirable ozone depleting properties because it does not contain any chlorine. The operating pressures of R-410A are approximately 50% to 70% higher than that of R-22. R-410A systems use synthetic polyol ester (POE) oil. Unfortunately, POE oils are hydroscopic, meaning they absorb water. This can degrade the oil, causing harm to the entire system. R-410A systems should not be left open to the atmosphere longer than absolutely necessary.

Reciprocating Compressor – A reciprocating compressor is a type of compressor used in air conditioners that compresses refrigerant by using a type of “piston” action.

Refrigerant Lines – Refrigerant lines are a set of two copper lines connecting the outdoor unit and the indoor unit.

Return Air – Return air is air drawn into a heating/cooling unit after having been circulated from the cooling/heating unit output supply to a room.

Return Air Box – The return air box the metal box that mounts directly to the return air grill.

Return Duct – The return duct blows air back through the cooling system.

Reversing Valve – A reversing valve is a device in a heat pump that reverses the flow of refrigerant as the system switches from cooling to heating.

SEER – SEER is an acronym for the Seasonal Energy Efficiency Ratio which is a measure of the cooling efficiency of your air conditioner or heat pump. The higher the SEER number, the more efficient the system is at converting electricity into cooling power.

Sensible Heat – SEnsible heat is energy that raises or lowers the temperature of a gas, liquid or solid when added or removed from that material.

Setpoint – Setppint is the temperature at which a thermostat is set for desired comfort level.

SHGF – SHGF is an acronym for Solar Heat Gain Factor

Split System – A split system refers to an air conditioner or heat pump that has components in two locations. Usually, one part of the system is located inside (evaporator coil) and the other is located outside your home.

Sub Cooling – Sub cooling is the cooling of a liquid , at a constant pressure, below the point at which it was condensed.

Suction Line – A suction line is a tube or pipe used to carry refrigerant gas from evaporator to compressor.

Superheat – Superheat is heat that is added to a vapor after all liquid has been vaporized.

Supplementary Heat – Supplementary heat is the emergency heat that is usually electrically resistance heat that is provided at temperatures below a heat pump’s balance point.

Temperature – Temperature is the measure of the intensity of heat that a substance possesses.

Thermostat – A thermostat is a temperature sensitive switch that controls the operation of a cooling and heating.

Ton – A ton is a unit of measure for cooling capacity. One ton = 12,000 BTUs per hour.

Under Sizing – Indersizing is the practice of selecting an air conditioner with a cooling capacity smaller than the cooling load.

Vacuum Pump – A vacuum pump is a pump used to remove air and moisture from a refrigeration system at a pressure below atmospheric pressure.

Vapor – Vapor is the gaseous state of a substance.

Velocity – Velocity is the speed at which a substance passes a point.

VOC – VOC is an acronym for Volatile Organic Content

Water Manometer – A water manometer is a device used to measure pressure in inches of water.

Zoning – Zoning is the practice of dividing a home into small sections for cooling and heating control. Each section is selected so that one thermostat can be used to determine its requirements.