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Making informed purchasing decisions and getting the best performance from your home comfort system is easier when you know the common terms.

The HVAC industry is stuffed full of jargon and vocabulary unfamiliar to the average consumer. Without an understanding of key terms like AFUE and SEER, it is nearly impossible to make an educated, informed furnace or air conditioner purchase. To help you learn the lingo and gain a little insight into the industry we love, here is a thorough list of HVAC terms and definitions.

A

ACCA
ACCA (Air Conditioning Contractors of America) is the association of HVAC (heating, ventilation, air conditioning, building performance) contractors.

AHRI (Air Conditioning, Heating and Refrigeration Institute)
AHRI is an abbreviation for the Air Conditioning, Heating and Refrigeration Institute, a trade association that develops standards for measuring and certifying product performance. AHRI standards and guidelines are used throughout the world. Equipment with the AHRI Certified® mark has AHRI’s assurance that it will perform accurately and consistently.

Air Conditioner
A system or an assembly comprised of components designed to control air temperature, relative humidity and air flow.

Air Handler
An air handler, or air handling unit, is the indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your home. It is usually a large metal box containing important elements of an HVAC system that controls airflow and filtration. 

Annualized Fuel Utilization Efficiency (AFUE)
A measure of furnace heating efficiency. The higher the AFUE, the more efficient the furnace.

B

Bioaerosols
Bioaerosols, or biological aerosols, are tiny airborne particles that are biological in nature. High concentrations of bioaerosols in indoor air can lead to respiratory problems and disease. Maintaining proper home humidity levels and installing advanced filtration devices can help reduce bioaerosols and maintain a healthy environment.

British Thermal Unit (BTU)
A measurement of heat energy. One Btu is the amount of heat required to raise one pound of water by one degree Fahrenheit. The higher the Btu rating, the greater the heating capacity of the system.

British Thermal Unit Per Hour (BTUh)
British thermal units per hour.

C

Capacity
The heating or cooling capabilities of a unit. Normally, this is displayed in BTUs.

Carbon Monoxide (CO)
Carbon monoxide (sometimes referred to by its chemical abbreviation, CO) is an odorless, colorless, tasteless and poisonous gas that’s produced when fuels such as natural gas burn with insufficient air. When carbon monoxide leaks into your home’s air, it can lead to serious health problems for your family. Regular maintenance of your home’s heating and ventilation system will help ensure it’s not a source of a carbon monoxide leak.

Central Air-Conditioning
Central air conditioning (or central A/C) is a system in which air is cooled at a central location and distributed to and from rooms by one or more fans and ductwork. 

Charge
The amount of refrigerant in a system.

Coil
There are typically two HVAC coils in a system—the condenser coil in the outside air conditioning condenser unit and the evaporator coil in the indoor unit. The coils are what increase or decrease the temperature via heat transfer.

Combined Annual Efficiency (CAE)
Combined Annual Efficiency (CAE) is a measure of the amount of heat produced for every dollar of fuel used to heat your home’s air and water. It is used to compare efficiencies of integrated water and space heaters.

Compressor
An AC or heat pump compressor is the part of an outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements.

Condenser
A condenser (or AC condenser) is the outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.

Cubic Feet Per Minute (CFM)
Cubic Feet Per Minute (CFM) is a measurement of airflow volume, determined by how many cubic feet of air pass by a stationary point in one minute. Having an accurate estimate of your home’s CFM is key to choosing an HVAC system with the right capacity for your space and needs.

D

Damper
A movable plate, located in the ductwork, that regulates airflow and redirects it to specific areas of the home. Dampers are typically used in zoning or “zone control” systems.

Decibel (dB)
A decibel (dB) is a unit used to measure the relative intensity of sound. For example, sound levels in a library are normally about 40 dB, normal conversations range from about 50 to 60 dB, and an operating motorcycle or garbage truck can be as high as 100 dB.

Department Of Energy (DOE)
The U.S. Department of Energy (DOE) is a federal agency responsible for monitoring the consumption of energy sources and setting industry efficiency standards for all heating and cooling units manufactured in the U.S.

Dry-Charged Unit
An air conditioner or heat pump that is shipped dry and charged with refrigerant at the place of installation. Dry-charged units are appropriate for homeowners who need a replacement unit compatible with R-22 refrigerant.

Dual Fuel
A comfort system that pairs an electric heat pump with a gas furnace and alternates between the two fuel sources to maximize comfort and efficiency.

Ductless Mini-Split
A type of air conditioning system that does not use ducts to transfer cool. Instead, the outdoor condenser unit is connected directly to an interior air handler. Because of this direct connection, generally only one room or space can be cooled at a time making ductless mini-splits a viable option for room additions or add-ons. Mitsubishi Electric is the industry standard when it comes to ductless systems; now offering options that connect to your existing ductwork.

Ductwork
Ductwork refers to the system of ducts (metal or synthetic tubes) used to transport air from heating, ventilation and air-conditioning (HVAC) equipment throughout your home. Properly installed and air ducts are a key component of indoor air quality and home comfort.

E

Electronic Air Cleaner
Electronic air cleaners, sometimes referred to as ionizers or electronic air purifiers, use electrically charged filters to reduce the number of airborne contaminants in your home. As air passes through your heating and cooling system, the cleaner uses electrically charged filters to attract and trap harmful particles to prevent them from recirculating through your home.

Energy Efficiency Ratio (EER)
The ratio of cooling capacity to the power input (in watts). The higher the EER rating, the more efficient the air conditioner.

Energy Star®
ENERGY STAR® is a program of the U.S. Environmental Protection Agency (EPA) designed to help consumers and businesses save money by choosing energy-efficient products and technologies. Heating, ventilation and air-conditioning (HVAC) equipment with the ENERGY STAR® label meets or exceeds federal guidelines for energy-efficient performance.

Environmental Protection Agency (EPA)
The U.S. Environmental Protection Agency (EPA) is a federal agency that develops and enforces federal environmental regulations and oversees the nationwide ENERGY STAR® program.

Evaporator Coil
The part of an air conditioner or heat pump that absorbs the heat from the air in your house. It is located inside the air handler or attached to the furnace.

F

Fresh Air Intake
An opening through which outdoor air is drawn into a system.

Furnace
The HVAC component that adds heat to indoor air by burning fuel in a heat exchanger.

G

Gas Furnaces
A gas furnace is the part of an HVAC system that converts natural gas or propane into high-temperate heat for the home.

H

Heat Exchanger
A heat exchanger is a heating component that is located in the furnace and transfers heat to the surrounding air, which is then pumped throughout the home.

Heat Pump
A heat pump is an HVAC unit that heats or cools by moving heat. During the winter, a heat pump draws heat from outdoor air and circulates it through a home’s air ducts. In the summer, it reverses the process and removes heat from the house and releases it outdoors.

Heating Seasonal Performance Factor (HSPF)
The heating efficiency rating for heat pumps. The higher the rating, the more efficient the heat pump.

Horizontal Flow
Describes an air handler or furnace that is positioned on its side and circulates air in one end and out the other. Ideal for attic or crawl space installations.

Humidifier
A humidifier is a device that adds moisture to indoor air in a single room or throughout an entire house. Whole-home humidifiers may use the fan in your furnace or air handler to blow humidified air throughout the ductwork, or they may work independently of your heating and cooling system to maintain humidity levels even when the furnace or air handler isn’t operating.

Humidity
A measure of the amount of moisture in the air.

Humidistat
A humidistat (sometimes called a humidistat control) is a device that works with a home’s heating and cooling system to automatically adjust the amount of moisture in the air to maintain a specific humidity level throughout the home.

HVAC
Heating, Ventilation and Air Conditioning.

I

Indoor Coil
See Evaporator Coil.

ISO 9000
A family of international standards for quality management and assurance.

M

Manual J Load Calculation
Manual J is the protocol used for determining the amount of heating and cooling that a home requires to keep its occupants warm in the heating months and cool and dry in the cooling months. 

Matched Systems
Simply put, matched systems are complete HVAC systems consisting of individually efficient products that realize even greater efficiency when paired together.

MERV Rating
The Minimum Efficiency Reporting Value (MERV) rating is used to rank the efficiency of air filters. Every air filter has holes that allow air and particles to pass through. The smaller the holes, the fewer particles that can pass through. Higher MERV ratings indicate smaller holes, and therefore a more efficient filter.

Micron
A unit of measure equal to one millionth of a meter, or 1/25,000 of an inch. Airborne particles – such as dust, dander, mold and viruses – are measured in microns. These tiny particles can circulate in your home’s air and have harmful effects on your family’s health and comfort.

O

Oil Furnace
An oil furnace is the part of an HVAC system that converts heating oil (similar to diesel) into high-temperate heat for the home.

Outdoor Coil
See Condenser.

P

Packaged Units
Heating and cooling systems contained in one outdoor unit.

Particles
Particles are tiny substances measuring less than 100 microns in diameter. Indoor air can be filled with particles, some of which can be seen with the naked eye, such as dust and dirt. Others can only be seen with a microscope, such as bacteria and viruses, which typically measure only one micron or smaller in diameter. All of these airborne particles can have significant impacts on your family’s health and comfort.

Programmable Thermostat
A programmable thermostat is a thermostat with the ability to adjust home heating and cooling equipment according to a pre-set schedule. For instance, a programmable thermostat could be set to maintain a home temperature of 72 degrees throughout the day, and 65 degrees from 11:00 p.m. to 7:00 a.m. every night.

R

R-22 Refrigerant
The old standard for residential air conditioners, now being phased out by the U.S. EPA. 

R-410A Refrigerant
A chlorine-free refrigerant that meets the U.S. EPA’s newest, most stringent environmental guidelines.

R-Value
R-value is a measurement of the effectiveness of your insulation. Depending on where you live, certain areas are recommended to have specific levels of insulation to keep their energy costs low. 

Refrigerant
A chemical that produces a cooling effect while expanding or vaporizing. Most residential air-conditioning units contain the standard R-22 refrigerant, or freon.

Refrigerant Lines
Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.

Register
A grille and damper assembly that covers the opening or end of an air duct.

Relative Humidity
The ratio of the amount of moisture in the air compared to the amount of moisture the air could hold at the current temperature, expressed as a percentage.

Return Air
The air drawn into the heating unit after having been circulated through a room.

S

Scroll Compressor
A specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Seasonal Energy Efficiency Ratio (SEER)
Seasonal Energy Efficiency Ratio (SEER) is an energy efficiency rating for air conditioners. The higher the SEER, the more efficient the unit.

Split System HVAC
A heating and cooling system that includes an indoor unit, outdoor unit and a thermostat.

Switchover Valve
The mechanism reverses the flow of the refrigerant to change from heating to cooling mode and back again.

T

Thermidistat
A thermidistat is a device that monitors indoor temperature, humidity levels and automatically adjusts your heating or cooling system to maintain desired levels.

Thermostat
A thermostat is a device that monitors the indoor temperature and automatically adjusts your heating or cooling system to maintain the desired level.

Ton
Unit of measurement for determining cooling capacity. One ton equals 12,000 Btuh.

Two-Stage Operation
Provides two levels of heating or cooling output for enhanced temperature control, energy efficiency and indoor air quality.

U

Ultraviolet Light or U.V. Light
Also known as a UV Lamp, a UV light is an air purifier that utilizes ultra-violet light to kill pathogens. This is normally attached to the evaporator coil or installed in the duct work near the furnace.

Upflow Furnace
Describes an air handler or furnace that is installed in an upright position and circulates air through the side or bottom and out through the top. Typically used in basements, closets and attic installations.

V

Variable Speed Motor
A motor that operates at a wide range of speeds to precisely control the distribution of heated and cooled air throughout the home.

Ventilator
A ventilator is a device that replaces the stale, recirculated air inside your home with fresh, filtered outdoor air. An energy recovery ventilator (ERV) is ideal for warm and humid climates, since it cools and dehumidifies the incoming outdoor air. A heat recovery ventilator (HRV) is more appropriate for colder climates, as it transfers heat from recirculated air to the fresh incoming air.

Z

Zoning
A zoning system (also referred to as “zoned HVAC”) is a heating and cooling system that uses dampers in the ductwork to regulate and redirect air to specific areas of the home. This allows for the creation of customized temperature zones throughout the home for increased comfort and efficiency.


Contact Pro-Tech HVAC Home today and let us take care of your heating and cooling needs, using the latest in modern HVAC technology. We’re always happy to help our Annapolis neighbors meet their home comfort goals!

Pro-Tech HVAC Home offers new installation, replacement, repairs and maintenance of heating and air conditioning systems in the Annapolis area. Our customers rely on us for honest and reliable service for air conditioners, heat pumps, gas furnaces, Mitsubishi systems, and more. We’re happy to answer questions, troubleshoot, and help you choose the best HVAC system for you and your family. We’re always happy to help answer your questions, so please give us a call or send us an email.

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About Us

Pro-Tech HVAC Home offers new installation, replacement and maintenance of heating and air conditioning systems in the Annapolis area. Our customers rely on us for honest and reliable service for air conditioners, heat pumps, gas furnaces, Mitsubishi systems, and more. We’re happy to answer questions, troubleshoot, and help you choose the best HVAC system for you and your family.