HVAC Glossary

If you’re unfamiliar with HVAC work, the terminology can become overwhelming, and it’s easy to feel like you’re in over your head. This glossary of terms will help you get a clearer picture of heating, cooling and indoor air quality products and enable you to make the right decisions for your home.

AFUE

Annual Fuel Utilization Efficiency (AFUE) is a metric for a furnace’s relative heating efficiency . A higher AFUE percentage is indicative of a more efficient furnace.

Airflow

Airflow refers to the relative movement or dispersal of air.

Air-Conditioning and Refrigeration Institute (ARI)

The Air-Conditioning and Refrigeration Institute (ARI) is an industry trade association which sets parameters for measuring and certifying a product’s performance. In example, the ARI Standard 270 sets guidelines for acceptable sound emissions of outdoor air-conditioning equipment.

Air Handler/Coil Blower

This refers to the indoor section of a heat pump or air conditioner that disperses heated or cooled air through a home’s ductwork. An air handler is typically either a blower coil or a furnace.

Bioaerosols

Bioaresols refer to microscopic bacteria, fungi and viruses suspended throughout the air which multiply in warm, humid places.

BTU

A British Thermal Unit (BTU) is the amount of heat required to elevate the temperature of one pound of water by one degree Fahrenheit, and is a commonly used unit of heat energy. A higher BTU rating signifies a greater heating capacity.

BTUH

British Thermal Units per Hour (BTUH) refers to a furnace’s relative heating capacity over time.

CAE

Combined Annual Efficiency (CAE) is a metric that measures the relative amount of heat produced for every dollar of fuel consumed, and is used to evaluate the efficiency of both home and water heaters.

Carbon Monoxide

Carbon Monoxide is an odorless, colorless and tasteless gas produced when carbon burns with an insufficient oxygen supply. It is fatal when inhaled and highly flammable.

Central Air Conditioning System

In a central air conditioning system, air is treated in a central location and distributed throughout the home with one or more fans through ductwork.

CFM

Cubic Feet per Minute (CFM) signifies how many cubic feet of air circulate past a stationary point in one minute. A higher CFM indicates that more air is moved through ductwork by a system.

Composite Fan Blades

Composite fan blades are manufactured with strengthened material and are angled to improve operation and durability. Composite fan blades are frequently used in outdoor heat pump or air conditioning units.

Compressor

A compressor is the component of an outdoor heat pump or air conditioner that compresses and pumps refrigerant to cool air.

Condenser Coil

The condenser coil either releases or collects heat in an outdoor heat pump or air conditioner, depending upon whether the air is being heated or cooled.

Damper

Dampers are movable plates in ductwork that regulate airflow, directing air to where it is most needed. Dampers are typically used where zoning is required.

dB

The decibel (dB) is used as a unit to measure sound’s relative intensity.

Dual Fuel

A dual fuel system pairs an electric heat pump with a gas furnace, and is more energy-efficient than conventional furnace/air conditioners combinations.

Ductwork

Ductwork is used to channel air from a furnace or blower coil throughout a building.

Electronic Air Cleaner

Electronic air cleaners filter large particles and bioaerosols from indoor air.

ENERGY STAR^®

ENERGY STAR^® is an Environmental Protection Agency (EPA) designation certifying that products meet or exceed government standards for efficiency.

EPA

The Environmental Protection Agency (EPA) establishes and implements federal environmental regulations, and oversees the ENERGY STAR^® program.

Evaporator Coil

The evaporator coil is located inside an air handler or furnace in an air conditioner or heat pump, and absorbs heat from a building’s air.

Garage Heaters

Garage heaters run on either natural or propane gas, or are used to heat garages and workshops. Garage heaters have heating capacities for various size garages to meet the needs of your application.

Grid-tied

A grid-tied unit refers to a solar heating unit in which the electric system of a building remains attached to the utility company’s network of power stations, which provides electricity when a solar system isn’t producing energy, such as at night. This is the most common and inexpensive residential solar system.

Heat Exchanger

The heat exchanger is located in the furnace, and transfers heat to surrounding air, which is then circulated throughout the building.

Heat Pump

A heat pump is a type of HVAC unit that heats or cools by moving heat. When a building needs to be heated, a heat pump draws heat from outdoor air and releases it into the building. For cooling, the heat pump removes heat from a building’s air and pumps it outdoors.

Horizontal Flow

Horizontal flow refers to when an air handler or furnace is positioned on its side, and moves air in one end and out the other. Horizontal flow is ideal in limited spaces, such as in attics and crawl spaces.

HSPF

Heating Seasonal Performance Factor (HSPF) is a heating efficiency metric for heat pumps. A higher HSPF is indicative of a more energy-efficiency heat pump.

Humidifier

Humidifier is an indoor air quality device that introduces moisture to heated air as it passes from the furnace into the ductwork for distribution throughout the home.

Humidistat

A humidistat is used to maintain humidity at a given setpoint, and is an automated device.

HVAC

Heating, Ventilation and Air Conditioning (HVAC) refers to products and systems used to heat, cool and circulate air in a building.

Indoor Coil

An indoor coil is the same thing as an evaporator coil.

ISO 9000

The ISO 9000 standards are used internationally to set guidelines for quality management and assurance.

MERV Rating

The Minimum Efficiency Reporting Value (MERV) rating of a filter describes the size of a filter’s pores. A higher MERV rating indicates that a filter is more efficicenty.

Micron

A micron is a unit of size equivalent to one millionth of a meter or one thousandth of a millimeter, and is frequently used to describe filters and particulate contaminants.

Odors/Chemicals

Odors and chemicals are gaseous air contaminants that often pose a problem in HVAC systems.

Off-grid or Off-the-grid

Off-grid or Off-the-grid electricity generating systems operate independently from the utility grid, and provide a home’s electricity in its entirety. Off-grid systems are more costly than grid-tied systems, but are ideal for homes in remote locations in which utility service is unavailable.

Outdoor Coil

An coil is the same as a condenser coil shown above.

Particles

Particles are described as any substance 100 microns or less in diameter. According to the EPA small particles measuring less than 2.5 microns are most hazardous.

Programmable Thermostat

A programmable thermostat is able to record different temperature and time settings for heating and cooling equipment.

R-22 Refrigerant

R-22 refrigerant was previously the standard coolant used in residential air conditioners, but the US EPA is now phasing R-22 out in favor of R-410A.

 

R-410A Refrigerant

R-410A refrigerant is chlorine-free and meets or exceeds the EPA’s new environmental guidelines.

Refrigerant

A refrigerant is a chemical that has a cooling effect when expanding or vaporizing. Most residential units utilize either R-22 or Freon.

 

Refrigerant Lines

The refrigerant lines are two copper lines that function to connect an outdoor air conditioner or heat pump to the evaporator coil located indoors.

Scroll Compressor

A scroll compressor is specially designed to work in a circular motion rather than in a conventional up-an-down piston motion.

SEER

Seasonal Energy Efficiency Ratio (SEER) is an energy efficiency rating for air conditioners. A higher SEER denotes a higher energy performance. The DOE requires a minimum SEER rating of 13.00.

SilentComfort™ Outdoor Fan Motor

This is used in some Lennox outdoor or air conditioner heat pump units, and is designed to optimize overall performance while keeping sound levels low using innovative electronic sensor technology.

Single Package

In a single package unit, a heating and cooling system are contained in one outdoor unit.

Split System

In a split system HVAC system, some components of the system are located inside a building and others are located outside. Split systems should be matched for maximal efficiency.

Thermidistat

Thermidistats monitor both temperature and humidity and adjust the heating or cooling system to maintain setpoints in both parameters.

Thermostat

The thermostat is usually installed on an inside wall, and operates as a control to regulate heating and cooling equipment to the desired temperature.

Ton

The ton unit is frequently used to measure the capacity of an air conditioner. However, it does not indicate the unit’s weight, but instead to its efficiency. A ton refers to a capacity of 12,000 BTUs per hour.

Two-Stage Operation

Two-stage operation allows for two levels of heating or cooling output for enhanced temperature control, energy efficiency and indoor air quality.

Upflow

Upflow refers to an air handler or furnace being installed in an upright position, in which air is circulated through the side or bottom and out the top. Upflow is frequently utilized in basement, attic and closet installations.

Variable Speed Motor

A variable speed motor automatically adjusts the flow of warm or cool air for optimal temperature maintenance.

Ventilator

Ventilator systems exchange stale, recirculated indoor air with filtered outdoor air.

Zoning

In zoning, a home is partitioned into independently controlled comfort zones for increased comfort and efficiency.