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HVAC Terminology

hvac terminology
Get To Know Your HVAC System

Learning common terminology about your heating, ventilation,and air conditioning (HVAC) system will help you better communicate with an HVAC professional and make better purchasing decisions. At LA Construction, Heating and Air we are committed to making sure our customers are well-informed about their HVAC systems. Below we highlight common HVAC terminology including basic components, so you have more of an understanding about how the HVAC system in your home keeps you comfortable year-round.


AFUE (Annual Fuel Efficiency Ratio) – Is the measurement of the energy efficiency of your heating system whether a furnace or a boiler. It measures how much fuel is used to heat your home vs. how much energy is lostthrough the exhaust. A furnace with 80% AFUE means that 80% of the fuel is converted to heat while 20% is lost through the exhaust. The higher the AFUE the more efficient the product.

Air Conditioner (AC) – A system that controls the humidity, ventilation, and temperature in a building or home, typically to maintain a cool atmosphere in warm conditions. A room air conditioner is installed in a window or on awall and delivers conditioned air without a duct system. A central air conditioner uses fans and ducts to disperse cooled air from the unit to the rooms in your home or in a building.

Air Conditioning – Is the process by which an air conditioner removes moisture and heat from the air to provide a more comfortable space.

Air Handler- Is the indoor unit that contains the blower and circulates the air through the duct system.



Balancing- The process of adjusting the flow of air in duct systems, or water flow in hot-water heating systems. Proper balancing is performed using accurate instrumentation to deliver the right amount of heating or cooling to each area or room of the home.

BTU(British Thermal Unit) – Is the amount of energy (heat) required to raise the temperature of one pound of water by one-degree Fahrenheit. In HVAC systems it indicates the rate of cooling, dehumidifying, or heating in an HVAC system.  

Burner- The device that facilitates the combustion of air and gas.

Burner Orifice- The opening in the burner through which the gas or fuel passes prior to combustion.



Capacity- HVAC capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.

CFM (Cubic Feet per Minute)- A measurement of airflow volume.

Chiller- Is a device that removes heat from a liquid through a vapor compression or absorption refrigeration cycle. The cooled liquid then flows through the pipes in a building and passes through the coils in air handlers,fan – coil units or other systems to cool and dehumidify the air.

Condenser- Is the outdoor unit of an air conditioning system and functions as a heat transfer point for collecting heat from and dispelling heat to the outside air.

Compressor- Is the pump inside the condenser that moves the refrigerant from the indoor evaporator coil to the outdoor condensing unit and back to the evaporator. It is responsible for circulating and raising the pressure of the refrigerant in your system.

Condensate-As warm air is pulled or pushed across the cool evaporator coil the coil perspires,creating liquid, or condensate which is mechanically drained away from the equipment.

Condenser Coil- A network of refrigerant-filled tubes where heat leaves the hot refrigerant vapor. The vapor then condenses into a liquid capable of absorbing more heat.



Damper- A device that located in the ductwork to adjust air flow. It is a movable plate that opens and closes to control airflow. There are two types of dampers: Manual and motorized. A manual damper generally consists of a sheet metal flap, shaped to fit the inside of a round or rectangular duct. By rotating a handle located outside of the duct a technician can adjust air flow to match the needs of an area or room. A motorized damper is generally used in a zoned system to automatically deliver conditioned air to specific rooms or zones.

Dehumidifier- Is equipment that reduces the level of humidity from the air. It works by cooling air to the point where water turns to liquid from vapor form, which is then removed.

Ductwork- Is a network of specialized pipes or channels for the airflow(including supply air, return air and exhaust air) within a home. Ducts can be made from several different materials including galvanized steel (the most common), aluminum, fiberglass, polyurethane, and plastic (called flexible ducting).



EER- The Energy Efficiency Ratio of a particular cooling device is the ratio of output cooling energy (in BTU) to input electrical energy at a given operating point. EER changes with the inside and outside conditions, falling as the temperature difference between inside and outside gets larger.

Energy Star®- ENERGY STAR is a U.S. Environmental Protection Agency (EPA) voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency

Evaporator Coil- The portion of a heat pump or central air conditioning system located in the home and functions as the heat transfer point for warming or cooling indoor air. It can be used to absorb heat from air or from a liquid.



Fan- A device consisting of a motor and a blower wheel that creates air flow.

Filter- The air filter is integral to the system intake ducting, the filter prevents contaminants from entering the equipment and must be maintained or replaced on a routine schedule.

Flue- A vent that removes the byproducts of combustion from a furnace.

Furnace- The unit responsible for heating a home. A furnace facilitates the combustion of fuel and air to create heat and then circulates it through the home by means of a fan.


Grille- The facing across a duct opening,often rectangular in shape, containing multiple parallel openings through which air may be delivered to a ventilated space. The grille directs the airflow in a particular direction and prevents the passage of debris.



Heat Exchanger-   A device through which heat is transferred to a cold or warm area or surface.

Heat Pump- Is a type of air conditioner that contains a valve that allows it to alternate between heating and cooling. A heat pump looks like a typical condensing unit, but it can use electricity to efficiently heat your home in the winter and also cool your home in the summer just like a standard air conditioning system.

HSPF- The acronym means Heating Seasonal Performance Factor. A measure of a heat pump's heating efficiency. The higher the HSPF, the more efficient the product.

Humidifier-A device that adds humidity, or moisture, to the air.

HVAC- The acronym for Heating, Ventilation and Air Conditioning.



IAQ- Indoor Air Quality characteristics of the indoor climate of a building, including the gaseous composition, temperature, relative humidity, and airborne contaminant levels.



Line Set- The two lines of refrigerant that connect the evaporator coil and condensing unit. The small, copper tube is the liquid line, while the large and more insulated tube is the suction line.

Load Calculation- This calculation determines how much heating or cooling your home needs.



MERV- Minimum Efficiency Reporting Value. This is how a filter is rated for your system. The higher the rating, the more efficient a filter is.



NATE- North American Technician Excellence is the nation’s largest non-profit certification organization for heating, ventilation, air conditioning and refrigeration technicians. NATE is the only technician certification organization governed,owned, operated, developed and supported by the HVACR industry.



Package Unit- A year-round heating and air conditioning system that has all of the components completely encased in one unit outside the home.

Plenum- This is the box that is attached to the side of the air handler where the ducts are attached. On the return side, you may find a filter between the air handler and the plenum. On the supply side, you may see the evaporator coil that is separately housed from the blower. The plenum is usually made of insulated sheet metal but can be made of other materials.



R-Value: A measure, in Btu/(ft2 F), of the resistance to transmission of heat by an insulating material. The higher the R-value of a material, the greater its insulating properties and the slower the heat flow through it. The specific value needed to insulate a home depends on climate,type of heating system and other factors.

Refrigerant- A substance that produces a refrigerating effect while expanding or vaporizing.Air conditioning systems use Refrigerant in the Evaporator Coil to cool air as it passes by. Refrigerants absorb heat in evaporator by change of state from a liquid to a gas and releases its heat in a condenser as the substance returns from the gaseous state back to a liquid state.

Register- Combination grille and damper assembly covering an air opening or end of an air duct. Coverings for the ducts where they open to the conditioned space.



SEER- Seasonal Energy Efficiency Ratio. It measures the efficiency of an air conditioner by taking the BTU/hour of cooling divided by the watts of electricity over an entire cooling season. The higher the unit’s SEER rating the more energy efficient it is and the more money you will save on your electric bills.

Split System- A heat pump or central air conditioning system with components located both inside and outside the home.



Thermostat–Typically found on an interior wall it is a temperature-control device that monitors and regulates a heating or cooling system.

Tonnage- This is a measure of the cooling capacity of the air conditioner. One ton of cooling is equal to 12,000 BTU/hour. It is used to measure how much heat the air conditioner can remove. Typical sizes for single family residences are between two and five tons.



Zoning- A system that divides a home, office or space into different regions in order to better control the temperature and effectiveness of a heating and cooling system independently. This can be achieved by installing multiple independent systems or by use of motorized dampers.


With all the terminology that exists in the HVAC industry,it can be easy to be overwhelmed and confused by your HVAC system. Reach out to us today by calling 818-341-3406 or contact us online if you need help understanding any terms or need to schedule service, we would be more than happy to assist!

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