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Knowledge Base

HVAC Glossary

Plain-language definitions of common heating, cooling and air-quality terms — search to find any term instantly.

Air Changes Per Hour (ACH)

The hourly ventilation rate divided by the volume of a space.

Air Conditioner

An appliance, system, or mechanism designed to dehumidify and extract heat from an area.

Air Conditioning & Refrigeration Institute (ARI)

An industry trade association that develops standards for measuring and certifying product performance.

Air Handler (AH)

The indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork.

Annualized Fuel Utilization Efficiency (AFUE)

A measure of furnace heating efficiency. The higher the AFUE, the more efficient the furnace.

Bioaerosol

A suspension of airborne particles that contain living organisms or were released from living organisms.

Boiler

An appliance intended to supply hot liquid or vapour for space-heating, processing, or power purposes.

British Thermal Unit (BTU)

A measurement of heat energy equal to the heat needed to raise one pound of water by one degree Fahrenheit.

British Thermal Unit Per Hour (BTUh)

The number of British thermal units of heating or cooling delivered per hour.

Capacitor

An electrical component that stores and releases energy to help start and run the motors in your AC or furnace.

Carbon Monoxide (CO)

An odourless, colourless, tasteless, poisonous and flammable gas produced when carbon burns with insufficient air.

Central Air-Conditioning System

A system in which air is cooled at a central location and distributed to and from rooms by fans and a series of ducts.

Coefficient of Performance (COP)

The ratio of heating or cooling delivered to the energy consumed, commonly used to rate heat pumps.

Combined Annual Efficiency (CAE)

A measure of the heat produced for every dollar of fuel consumed for both home and water heating.

Communication Module

A component that shows the system status and environmental benefits in real time.

Compressor

The part of an outdoor air conditioner or heat pump that compresses and pumps refrigerant.

Condensate Pump

A small pump that removes water produced by an AC or high-efficiency furnace when gravity drainage is not possible.

Condenser Coil

The outdoor portion of an air conditioner or heat pump that either releases or collects heat.

Contactor

An electrically controlled switch that supplies power to the compressor and condenser fan.

Cubic Feet Per Minute (CFM)

A measurement of how many cubic feet of air pass a stationary point in one minute.

Damper

A movable plate in the ductwork that regulates airflow and directs it to the areas that need it most.

Decibel (dB)

A unit used to measure the relative intensity of sound.

Defrost Cycle

A heat pump's automatic process of melting frost off the outdoor coil during cold weather.

Dehumidifier

An indoor air quality product that removes excess moisture from the air for comfort and mold prevention.

Dry-Charged Unit

An air conditioner or heat pump that is shipped dry and charged with refrigerant at the place of installation.

Dual Fuel

A comfort system that pairs an electric heat pump with a gas furnace and alternates between fuel sources for efficiency.

Ductless / Mini-Split System

A heating and cooling system with an outdoor unit connected to one or more indoor units, requiring no ductwork.

Ductwork

A system of ducts used to distribute air, as in a ventilation or heating and cooling system.

ECM Motor

An Electronically Commutated Motor: a highly efficient, variable-speed blower motor that lowers energy use and improves comfort.

Electronic Air Cleaner

An electronic device that filters out large particles and bioaerosols in indoor air.

Energy Efficiency Ratio (EER)

A measure of an air conditioner's cooling efficiency at a single peak operating condition.

Energy Recovery Ventilator (ERV)

A ventilator that swaps stale indoor air for fresh outdoor air while transferring both heat and moisture to save energy.

ENERGY STAR

A designation of the U.S. Environmental Protection Agency identifying energy-efficient products.

Environmental Protection Agency (EPA)

A U.S. government agency that develops and enforces federal environmental regulations.

Evaporator Coil

The part of an air conditioner or heat pump that absorbs heat from the air inside your home.

Flame Sensor

A safety device that confirms the burner has ignited and shuts off the gas if no flame is detected.

Fresh Air Intake (FAI)

An opening through which outside air is drawn into the building.

Furnace

An appliance fired by gas, oil, or wood in which air or water is heated to be circulated throughout a building.

Furnace Filter

A device between the return-air vent and the furnace that protects components and improves indoor air quality.

Garage Heater

A natural-gas or propane unit that provides warmth for car garages during the winter months.

Geothermal Heat Pump

A highly efficient system that exchanges heat with the stable temperature of the ground through buried loops.

Grille

A facing across a duct opening, often rectangular, containing multiple parallel slots.

Heat Exchanger

A heating component located in the furnace that transfers heat to the surrounding air.

Heat Pump

An HVAC unit that heats or cools by moving heat between the indoor and outdoor environments.

Heat Recovery Ventilator (HRV)

Like an ERV but transfers heat only, making it well suited to colder climates.

Heating Seasonal Performance Factor (HSPF)

The heating efficiency rating for heat pumps. The higher the rating, the more efficient.

HEPA Filter

A High-Efficiency Particulate Air filter that captures 99.97% of particles 0.3 microns and larger.

Horizontal Flow

An air handler or furnace positioned on its side that draws air in one end and out the other.

Hot Surface Igniter

A modern furnace component that glows hot to ignite the gas, replacing the old standing pilot light.

Humidifier

An indoor air quality product that adds moisture to heated air distributed through the ductwork.

Humidistat

An automatic device used to maintain humidity at a fixed or adjustable set point.

HVAC

Heating, Ventilation and Air Conditioning.

HVAC/R

Heating, Ventilation, Air Conditioning and Refrigeration.

Indoor Air Quality (IAQ)

The air quality within and around buildings as it relates to occupant health and comfort.

Installer

Any individual, firm, corporation, or company engaged in the installation of HVAC equipment.

Inverter Compressor

A compressor that continuously varies its speed to match demand, improving efficiency, comfort and quietness over fixed-speed units.

Latent Heat

Heat associated with changing the moisture content (humidity) of the air.

Load Calculation (Manual J)

The industry-standard method of sizing HVAC equipment based on a home's specific heating and cooling needs.

MERV Rating

Minimum Efficiency Reporting Value. It rates how effectively a filter captures particles; a higher MERV traps smaller particles.

Micron

A unit of measure equal to one millionth of a metre, or one thousandth of a millimetre.

Modulating Furnace

A furnace that adjusts its flame and output in small increments for very precise, efficient comfort.

NATE Certification

North American Technician Excellence, a respected certification proving an HVAC technician's knowledge and skill.

Packaged Unit

A complete heating and cooling system contained in a single outdoor unit.

Particles

Any airborne substances measuring less than 100 microns in diameter.

Plenum

The central air-distribution box attached to the furnace or air handler that connects to the supply and return ducts.

Programmable Thermostat

A thermostat that can store different temperature settings for different times of day.

R-22 Refrigerant

The older standard of refrigerant that is now being phased out.

R-32 Refrigerant

A newer refrigerant with a lower global-warming potential, increasingly used in modern systems.

R-410A Refrigerant

A newer, chlorine-free standard of refrigerant used in modern systems.

Refrigerant

A chemical that produces a cooling effect as it expands (liquid) or vaporizes (gas).

Return & Supply Air

Return air is drawn from the rooms back to the system; supply air is the conditioned air delivered to the rooms.

Scroll Compressor

A specially designed compressor that compresses refrigerant in a smooth, circular motion.

Seasonal Energy Efficiency Ratio (SEER)

An energy-efficiency rating for air conditioners. The higher the SEER, the more efficient.

SEER2

The updated efficiency standard for ACs and heat pumps, measured under more realistic, higher-pressure test conditions than the original SEER.

Sensible Heat

Heat that changes the air's temperature without changing its moisture content.

Smart Thermostat

A Wi-Fi-connected thermostat that learns your schedule and can be controlled remotely from your phone for added savings.

Split System

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

Static Pressure

The resistance to airflow within a duct system; excessive static pressure reduces efficiency and comfort.

Subcooling

The temperature of liquid refrigerant below its condensing point, used to verify a proper refrigerant charge.

Superheat

The temperature of refrigerant vapour above its boiling point, used to diagnose and charge a system correctly.

Thermostat

A unit that allows homeowners to monitor and adjust their heating and cooling equipment.

Thermostatic Expansion Valve (TXV)

A device that precisely meters refrigerant flow into the evaporator coil for efficient operation.

Ton

A unit of measurement for cooling capacity. One ton equals 12,000 BTUh.

Two-Stage Operation

Provides two levels of heating or cooling output for more consistent, efficient temperature control.

Upflow

An air handler or furnace installed in an upright position that discharges air upward.

UV Air Purifier

A device that uses ultraviolet light to reduce mold, bacteria and viruses in the air stream.

Variable Refrigerant Flow (VRF)

An advanced commercial system that can heat some zones while cooling others at the same time.

Variable-Speed Motor

A motor that operates across a wide range of speeds to precisely control the distribution of conditioned air.

Ventilator

A system that exchanges stale, recirculated indoor air with fresh, filtered outside air.

Water Heater

A household appliance with a gas or electric heating unit under a tank that stores heated water.

Zoning System

A system that divides a building into independently controlled zones for tailored comfort and efficiency.

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