HVAC Glossary

Common HVAC terms in one place.
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Filter by Topic: All Topics AC Refrigerant Energy Efficiency HVAC Accessory HVAC Certification HVAC Component HVAC Sizing HVAC System Indoor Air Quality Measurements Thermostat Thermostat Settings Thermostat Wiring

A

AC Recharge

AC recharge refers to the process of adding or replacing the refrigerant in an air conditoner or a heat pump...

Energy Efficiency

AFUE

AFUE (Annual Fuel Utilization Efficiency) measures how effectively a furnace or boiler converts fuel (natural gas or propane) into usable...

HVAC Certification

AHRI Certification

AHRI stands for the Air-Conditioning, Heating, and Refrigeration Institute. It is a North American trade association that represents manufacturers of...

Air Conditioner

An air conditioner is an HVAC system that helps regulate temperature and humidity in your home. The unit works by...

Indoor Air Quality

Air Filter

An air filter is a component installed in an HVAC system to capture dust, dirt, pet dander, pollen, and other...

Air Handler

An air handler is a part of an HVAC system that circulates conditioned air throughout your home. It works in...

Indoor Air Quality

Air Purifier

An air purifier is a device designed to clean indoor air by removing airborne particles, allergens, gases, and microorganisms. Indoor...

HVAC Certification

ASHRAE Certification

ASHRAE certification is a professional credential provided by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. It serves as...

Thermostat Settings

Auto Changeover Thermostat

An auto changeover is a thermostat feature that automatically switches an HVAC system between heating and cooling modes to maintain...

Thermostat Settings

Auxiliary Heat

Auxiliary heat, commonly shown as AUX on thermostats, is a secondary or backup heating source used by heat pump systems...

Thermostat Settings

Auxiliary Lockout

In extreme weather conditions, heat pumps become less efficient and rely on a backup heating source called auxiliary heat to...

B

Boiler

A boiler is a heating system that generates heat by boiling water and distributing it throughout a building to provide...

British Thermal Unit (BTU)

British Thermal Unit (BTU) is the amount of heat required to raise the temperature of one pound of water by...

C

Thermostat Wiring

C-Wire Adapter

A Common Wire Adapter, often called a C-wire adapter (CWA), is a device that provides a dedicated C-wire (common wire)...

Energy Efficiency

Carbon Footprint

A carbon footprint is the total amount of greenhouse gases emitted into the atmosphere by the activities of an individual,...

Central Air Conditioner

A central air conditioner cools your home by circulating conditioned air through a system of supply and return ducts. It...

Energy Efficiency

Coefficient of Performance

COP stands for the Coefficient of Performance and measures how efficiently an HVAC system operates. It compares the amount of...

Cold-Climate Heat Pump

A cold-climate heat pump is designed to heat homes even in extreme weather, with some systems performing reliably down to...

Energy Efficiency

Combined Annual Efficiency

Combined Annual Efficiency (CAE) measures the amount of heat delivered per unit of fuel cost. It indicates how efficiently a...

Compressor

A compressor is one of the most critical components of an HVAC system, located in the outdoor unit. It is...

Cubic Feet Per Minute (CFM)

Cubic feet per minute (CFM) is the measurement of how much air moves through a space in one minute. In...

D

Damper

HVAC dampers are small, adjustable valves or metal plates installed inside ductwork to regulate airflow. They allow you to divide...

Indoor Air Quality

Dehumidifier

A dehumidifier is a device that removes excess moisture from the air, helping to maintain ideal humidity levels. Reducing excess...

Energy Efficiency

Department of Energy (DOE)

The U.S. Department of Energy (DOE) is a federal agency established in 1977 to oversee national energy and nuclear research...

Dual-Transformer System

A dual-transformer HVAC system uses two independent transformers: one dedicated to heating and the other to cooling. This setup is...

Ductless Heat Pump

A ductless heat pump is an HVAC unit that heats or cools a room without needing any ductwork. The system...

Ductwork

Ductwork refers to the network of tubes or channels that carry heated or cooled air from an HVAC system to...

E

Energy Efficiency

EER2

The Energy Efficiency Ratio (EER) is a key metric used by the US Department of Energy (DOE) to measure the...

Thermostat Settings

Emergency Heat

Emergency heat, or EM heat, is a backup heating source used only when your heat pump is non-operational or is...

Energy Efficiency

ENERGY STAR®

ENERGY STAR ® is a certification program developed by the US Environmental Protection Agency (EPA) to identify and promote energy-efficient...

Energy Efficiency

Energy Tax Credit

Energy tax credits are government-backed incentives for homeowners and businesses to invest in energy-efficient technologies and systems. These credits encourage...

Energy Efficiency

EPA

The Environmental Protection Agency (EPA) is a U.S. federal agency responsible for protecting human health and the environment by regulating...

F

Fan Coil Unit

Fan Coil Units (FCU) are standalone systems that use a fan and a coil to provide heating or cooling without...

Energy Efficiency

Fan Energy Rating

The Fan Energy Rating (FER) is a standard set by the US Department of Energy (DOE) that measures the airflow...

Furnace

A furnace is an HVAC system that generates heat and distributes it throughout indoor spaces using ducts and vents. It...

G

Geofencing Thermostat

A geofencing thermostat is a smart thermostat that creates a virtual boundary or “geofence” around your home and automatically adjusts...

Geothermal Heat Pump

Geothermal heat pumps, also called ground-source or geo-exchange systems, use the earth’s stable underground temperature to heat and cool your...

Energy Efficiency

Global Warming Potential

Global Warming Potential (GWP) measures how much heat a greenhouse gas traps in the Earth’s atmosphere over a set period....

H

Heat Exchanger

A heat exchanger is one of the most essential components in an HVAC system. It is responsible for safely and...

Heat Pump

A heat pump is an HVAC system that heats and cools your home by moving heat rather than generating it....

Energy Efficiency

Heating Capacity Ratio (HCR)

The Heating Capacity Ratio (HCR) is a performance metric that indicates how effectively a heat pump maintains its heating capacity...

Energy Efficiency

HSPF2

HSPF stands for Heating Seasonal Performance Factor and measures how efficiently a heat pump provides heat over an entire heating...

Indoor Air Quality

Humidifier

A humidifier adds moisture to indoor air, helping maintain ideal humidity levels. It’s particularly beneficial during dry winter months, easing...

Indoor Air Quality

Humidistat

A humidistat is a humidity monitoring tool that helps maintain ideal humidity levels in a space. Also known as a...

HVAC

HVAC stands for Heating, Ventilation, and Air Conditioning. It is an umbrella term to describe systems that control indoor temperature...

Hydrofluoroolefins (HFOs)

Hydrofluoroolefins (HFOs) are a new generation of refrigerants composed of hydrogen, fluorine, and carbon. They are an eco-friendly alternative developed to...

Indoor Air Quality

Hygrometer

A hygrometer is a device used to measure humidity levels in your home. Humidity refers to the amount of water...

I

Indoor Air Quality

Indoor Air Quality (IAQ)

Indoor air quality (IAQ) refers to the levels of pollutants in indoor spaces and how they affect the health and...

Inverter Heat Pump

An inverter heat pump uses a variable-speed compressor that adjusts its output as needed, making it more efficient than a...

J

Thermostat Wiring

Jumper Wires

In HVAC systems, jumper wires are those handy little electrical wires that connect two terminals on a thermostat or HVAC...

L

Load Calculation

HVAC load calculation is the process of determining the heating and cooling requirements of your home in order to find...

M

Matched System

A matched system consists of different indoor and outdoor HVAC components designed to work together for optimal performance and efficiency....

Indoor Air Quality

MERV

MERV, short for Minimum Efficiency Rating Value, measures the effectiveness of an air filter. The higher the rating, the better...

Micron

A micron, or a micrometer, is a unit of measurement equivalent to one-millionth of a meter. 1 micron = 0.000001...

Mini-Split

A mini-split provides zoned heating and cooling for specific rooms without requiring ductwork. It’s easy to install and is ideal...

N

N+1

The N+1 redundancy in HVAC is about adding an additional unit (+1) beyond the number required to meet normal load...

HVAC Certification

NATE Certification

NATE Certification is a credential awarded by North American Technician Excellence, a non‑profit organization, to HVACR professionals. NATE ensures that...

Non-Programmable Thermostat

A non-programmable thermostat, or a manual thermostat, is a basic temperature control device that requires users to adjust the temperature...

O

O/B Reversing Valve

The O/B reversing valve in a heat pump controls the changeover between heating and cooling modes. It works by reversing...

Operating Cost

The HVAC operating cost is the total cost of running and maintaining your HVAC system over a year, including air...

P

Indoor Air Quality

Pleated Filters

Pleated filters are a type of air filter installed in HVAC systems, air purifiers, and other IAQ devices. They use...

Programmable Thermostat

A programmable thermostat lets you adjust your home heating and cooling automatically according to preset schedules. You can program different...

R

R-410A Refrigerant

R-410A refrigerant was widely used in air conditioners and heat pumps from around 2010 to 2023. It is a hydrofluorocarbon...

R-454B Refrigerant

What Is a Refrigerant? A refrigerant is a chemical substance used in air conditioning and refrigeration systems. It is found...

Recovery Mode

Thermostat recovery mode starts heating or cooling earlier than your scheduled time. Instead of waiting for the set time to...

Refrigeration Cycle

The refrigerant cycle is the process by which the refrigerant circulates through the four main components of an HVAC system:...

S

Scroll Compressor

A compressor is a key component of your HVAC system that compresses the refrigerant, allowing it to move through the...

Energy Efficiency

SEER2

SEER measures how efficiently an air conditioner or heat pump cools your home over an entire cooling season. The higher...

Sensible Heat

Sensible heat is the heat energy that causes a change in temperature of a substance but doesn’t modify its state....

Setback Thermostat

Thermostat setback is the practice of adjusting your thermostat during specific periods to lower energy consumption. Also called a setback...

T

Two-Stage Cooling

A two-stage cooling system relies on a compressor that can operate at two different capacities. Instead of running at 100%...

Two-Stage Heating

Two-stage heating refers to an HVAC system that can operate at two distinct output stages or capacities to meet your...

U

Indoor Air Quality

UV Lights

Ultraviolet lights are used to kill microorganisms such as viruses, bacteria, and fungi. In HVAC systems, UV lights are installed...

V

Variable-Speed Motor

A variable-speed motor is an advanced technology utilized by modern HVAC systems. It allows your unit to run at different...

Indoor Air Quality

Ventilator

A ventilator plays a crucial role in enhancing indoor air quality by managing the flow of fresh air into a...

W

Wet Switch Flood Detector

A wet switch flood detector in HVAC systems is a crucial safety device that detects water and prevents damage from...

Z

Zoning

A zoning system divides your home into multiple zones, each controlled by its own thermostat. Instead of using a single...

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