Learn The Lingo With Our Detailed Glossary
Welcome to our comprehensive guide on HVAC terminology. Whether you're a homeowner looking to understand your heating and cooling system better, an aspiring HVAC technician, or simply someone interested in learning more about this essential aspect of modern living, this page provides clear and concise definitions of key terms in the HVAC industry.
From fundamental concepts like air conditioning and heat pumps to specific components such as compressors and evaporator coils, our glossary covers a wide range of terms to help you navigate the complexities of HVAC systems. Understanding these terms will not only enhance your knowledge but also enable you to make informed decisions about installation, maintenance, and troubleshooting of your HVAC equipment.
A
AC (Air Conditioning): A system or process for controlling the temperature, humidity, and sometimes the purity of the air in an interior space.
ACCA (Air Conditioning Contractors of America): A non-profit association that represents HVAC contractors and promotes professional standards in the industry.
A-Coil: A type of evaporator coil that is shaped like an "A" and is commonly used in residential air conditioning systems.
AC or DC (Alternating Current or Direct Current): Types of electrical current; AC is commonly used in homes and businesses, while DC is used in battery-powered devices.
Acoustical: Related to sound; in HVAC, it often refers to the control of noise generated by HVAC systems.
AFUE (Annual Fuel Utilization Efficiency): A measure of the efficiency of a furnace or boiler, representing the percentage of fuel converted into usable heat.
AGA (American Gas Association): An organization representing natural gas companies, promoting safety, and advancing the use of natural gas.
AHRI (Air-Conditioning, Heating, and Refrigeration Institute): A trade association that develops standards for the HVACR industry and certifies equipment performance.
Air cleaner (also Air Filtration System): A device that removes contaminants from the air to improve indoor air quality.
Air Conditioner: A device or system that cools and dehumidifies the air in a space.
Air Filtration System (also Air Cleaner): Equipment used to remove particulates and contaminants from the air, improving indoor air quality.
Air flow volume: The amount of air moving through a space, usually measured in cubic feet per minute (CFM).
Air handler: The component of an HVAC system that circulates and conditions air, typically including a blower, heating or cooling elements, and filter.
ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers): A professional association seeking to advance HVACR technology and set industry standards.
B
BTU (British Thermal Unit): A unit of energy used to measure heating and cooling capacity, defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
BTUH (British Thermal Units per Hour): A unit of power representing the rate of energy transfer, used to quantify heating and cooling system capacities.
Burner: The component in a furnace or boiler where fuel is mixed with air and ignited to produce heat.
Burner Orifice: The opening in a burner through which fuel passes before being ignited.
Burner (sealed combustion): A burner that draws air from outside the home for combustion, improving efficiency and safety.
C
CADR (Clean Air Delivery Rate): A rating indicating the volume of filtered air delivered by an air cleaner, measured in cubic feet per minute (CFM).
Capacity: The ability of an HVAC system to heat or cool a given space, usually measured in BTUs or tons.
Celsius: A temperature scale where water freezes at 0 degrees and boils at 100 degrees, used internationally.
Certified Matched System: An HVAC system where all components are tested and certified to work together for optimal performance and efficiency.
CFM (Cubic Feet per Minute): A measure of the volume of air moved by a system or component, such as a fan or blower.
Charge: The amount of refrigerant in an HVAC system, crucial for proper operation and efficiency.
Comfort™ coil (also evaporator coil or indoor coil): The coil in an air conditioner or heat pump that absorbs heat from indoor air, often branded as Comfort™.
Compressor: A component in an air conditioning or refrigeration system that increases the pressure and temperature of refrigerant vapor.
Condensate: The liquid formed when moisture in the air condenses, often collected and drained away in HVAC systems.
Condenser coil (or outdoor coil): The coil in an air conditioning or heat pump system where heat is released to the outdoor air.
Condenser fan: The fan that moves air across the condenser coil to aid in the heat release process.
Contactor: A relay that switches electrical power to HVAC components like compressors and fans.
Crankcase heater: A heater used in compressors to prevent refrigerant migration and oil dilution during off-cycles.
CSA (Canadian Standards Association): An organization that develops standards and certifies products for safety and performance in Canada.
D
Damper: A device that regulates airflow in ducts or vents, controlling the volume and direction of air in an HVAC system.
DB (Decibels): A unit of measure for sound intensity, used to describe the noise level of HVAC systems.
DC (Direct Current): A type of electrical current that flows in one direction, commonly used in battery-powered devices.
Defrost: A process that removes frost or ice buildup from HVAC components, particularly in heat pumps.
Degree-day: A measure of heating or cooling demand, calculated as the difference between outdoor temperature and a baseline indoor temperature over a 24-hour period.
Dehumidifier: A device that removes excess moisture from the air to improve comfort and prevent mold growth.
Diffuser: A device that distributes air evenly in a space, often installed in ceilings or walls.
DOE (Department of Energy): A U.S. government agency responsible for setting energy efficiency standards and regulations for appliances, including HVAC systems.
Downflow furnace: A furnace designed to blow heated air downward into ducts below the unit.
Drain pan: A tray that collects condensate from HVAC systems, preventing water damage.
Dry bulb temperature: The air temperature measured with a standard thermometer, without accounting for humidity.
Dry bulb thermometer: A standard thermometer used to measure air temperature.
Dual Compressors: An HVAC system feature with two compressors, providing better efficiency and staging capabilities.
Ductwork: A system of ducts that distribute conditioned air throughout a building.
DX (Direct Expansion): A type of HVAC system where refrigerant evaporates directly in the coil to cool the air.
E
Ecologic: Relating to environmentally friendly and energy-efficient HVAC systems.
EER (Energy Efficiency Ratio): A measure of an air conditioner's efficiency, calculated as the cooling capacity (BTUs) divided by the power input (watts).
Electronic Air Cleaner (EAC): A device that uses electrically charged plates to remove particles from the air.
EPA (Environmental Protection Agency): A U.S. government agency responsible for protecting human health and the environment, including regulations for HVAC refrigerants.
Evaporator coil (also Comfort™ Coil or Indoor coil): The coil in an air conditioner or heat pump that absorbs heat from indoor air.
Expansion valve: A device that regulates the flow of refrigerant into the evaporator coil, controlling cooling capacity and efficiency.
F
Fahrenheit: A temperature scale where water freezes at 32 degrees and boils at 212 degrees, commonly used in the United States.
Fan: A device that moves air in HVAC systems, used for ventilation, cooling, and heating.
Filter: A device that removes particles from the air, protecting HVAC equipment and improving indoor air quality.
Flue: A duct or pipe that vents combustion gases from a furnace or boiler to the outdoors.
Furnace: A heating device that generates and distributes warm air through a building.
Fuse: A safety device that protects electrical circuits from overcurrent, used in HVAC systems to prevent damage.
G
GAMA (Gas Appliance Manufacturers Association): A trade association representing manufacturers of gas appliances, now part of AHRI.
Gas furnace heat exchanger: The component in a gas furnace that transfers heat from combustion gases to the air being heated.
H
Heat exchanger: A device that transfers heat between two or more fluids, used in HVAC systems for heating and cooling.
Heat gain: The increase in temperature in a space due to internal and external heat sources.
Heating coil: A coil that heats air in an HVAC system, typically using electric resistance or hot water.
Heat loss: The decrease in temperature in a space due to heat escaping to the outside.
Heat pump: An HVAC system that can both heat and cool a space by reversing the flow of refrigerant.
Heat transfer: The movement of heat from one area to another, a fundamental principle in HVAC systems.
HEPA filter (High-Efficiency Particulate Air filter): A type of air filter that can trap very small particles, improving indoor air quality.
Hertz: A unit of frequency, representing the number of cycles per second of an alternating current.
Horizontal flow: An HVAC system configuration where air flows horizontally through the unit.
HSPF (Heating Seasonal Performance Factor): A measure of the efficiency of a heat pump in heating mode, calculated as the total heating output divided by the total energy input.
Humidifier: A device that adds moisture to the air to improve indoor comfort and prevent dry conditions.
Humidistat: A device that measures and controls humidity levels in an indoor space.
Humidity: The amount of moisture in the air, affecting comfort and indoor air quality.
Humidity, absolute: The total amount of moisture in the air, usually measured in grams per cubic meter.
Humidity, relative: The percentage of moisture in the air relative to the maximum amount the air can hold at a given temperature.
HVAC (Heating, Ventilation, and Air Conditioning): The systems and technologies used to control the temperature, humidity, and air quality in indoor spaces.
Hybrid heat (also Hybrid System): An HVAC system that combines a heat pump with a traditional furnace for improved efficiency and comfort.
Hybrid system (also Hybrid Heat): See "Hybrid heat."
I
Ignition: The process of igniting fuel in a furnace or boiler to produce heat.
Indoor coil (also Comfort™ Coil or evaporator coil): The coil in an HVAC system that absorbs heat from indoor air.
Indoor/Outdoor system (also split system): An HVAC system with separate indoor and outdoor units, connected by refrigerant lines.
Inverter Compressor: A compressor that adjusts its speed to match the heating or cooling demand, improving efficiency and comfort.
K
Kilowatt (kW): A unit of power equal to 1,000 watts, used to measure electrical consumption.
L
Latent heat: The heat required to change the state of a substance (e.g., from liquid to gas) without changing its temperature.
Load calculation: A process to determine the heating and cooling requirements of a building, ensuring the HVAC system is properly sized.
M
Media: Materials used in filters and air cleaners to capture and remove particles from the air.
N
NATE (North American Technician Excellence): An organization that certifies HVAC technicians based on their knowledge and skills.
NEC (National Electrical Code): A set of standards for electrical installations in the United States, including guidelines for HVAC systems.
NEMA (National Electrical Manufacturers Association): A trade association that sets standards for electrical equipment, including HVAC components.
O
OEM (Original Equipment Manufacturer): A company that produces components or systems used in HVAC equipment, often branded by another company.
Operating cost: The cost to run an HVAC system, including energy consumption, maintenance, and repairs.
Orifice: An opening through which fluid or gas passes, used to control flow in HVAC systems.
Outdoor coil (also Condenser coil): See "Condenser coil."
P
Packaged system (or Packaged unit): An HVAC system with all components contained in a single unit, typically installed outdoors.
Packaged unit (or Packaged system): See "Packaged system."
Payback analysis: An evaluation of the time required for energy savings to offset the initial cost of an HVAC system.
PSI (Pounds per Square Inch): A unit of pressure, used to measure the force exerted by a fluid or gas in HVAC systems.
PSIA (Pounds per Square Inch Absolute): A measure of pressure relative to a perfect vacuum.
PSIG (Pounds per Square Inch Gauge): A measure of pressure relative to atmospheric pressure.
PVC (Polyvinyl Chloride): A type of plastic commonly used for pipes and fittings in HVAC systems.
R
Reciprocating compressor: A type of compressor that uses pistons to compress refrigerant, commonly used in HVAC systems.
Reclaiming: The process of recovering and cleaning refrigerant from HVAC systems for reuse.
Recycling: The process of reprocessing used materials for use in new products, including refrigerants in HVAC systems.
Refrigerant: A fluid used in HVAC systems to transfer heat, changing state between liquid and gas.
Refrigerant charge: The amount of refrigerant in an HVAC system, essential for proper operation and efficiency.
Refrigerant lines: Tubes that carry refrigerant between the components of an HVAC system.
S
SEER (Seasonal Energy Efficiency Ratio): A measure of an air conditioner's efficiency over a cooling season, calculated as the total cooling output divided by the total energy input.
Self-contained system: An HVAC system where all components are housed in a single unit.
Sensible heat: The heat that changes the temperature of a substance without changing its state.
Sensor: A device that detects and measures physical properties, such as temperature or humidity, used to control HVAC systems.
Setpoint: The desired temperature or humidity level set on a thermostat or controller.
Spine-Fin™ coil: A type of coil with a unique design for increased heat transfer efficiency, branded by a specific manufacturer.
Split system (also indoor/outdoor system): See "Indoor/Outdoor system."
T
Thermostat: A device that controls the temperature of a space by regulating the operation of an HVAC system.
Thermostatic expansion valve: A device that regulates the flow of refrigerant into the evaporator coil based on temperature.
Ton: A unit of cooling capacity, equal to 12,000 BTUs per hour.
Two-stage compressor: A compressor that operates at two different capacities, improving efficiency and comfort.
Two-stage heating/Two-stage cooling: An HVAC system with two levels of heating or cooling output, providing better efficiency and comfort.
U
U-Factor: A measure of heat transfer through a building component, used to evaluate insulation performance.
UL (Underwriters Laboratories): An organization that tests and certifies products for safety, including HVAC equipment.
Upflow furnace: A furnace designed to blow heated air upward into ducts above the unit.
V
Vacuum: A space devoid of matter; in HVAC, it often refers to the process of removing air and moisture from refrigerant lines.
Volt: A unit of electric potential, used to measure the electrical supply to HVAC equipment.
Voltage: The electric potential difference between two points, used to power HVAC systems.
W
Watt: A unit of power, used to measure the energy consumption of HVAC equipment.
Wet Bulb Thermometer: A thermometer with a wet bulb that measures temperature and humidity, used in HVAC to assess cooling efficiency.
Z
Zoning: The division of a building into different areas with independent HVAC control, improving comfort and efficiency.
Zoning System: An HVAC system with multiple zones, each with its own thermostat and control.
