Glossary of Terms

AFUE

Annualized Fuel Utilization Efficiency is the fuel efficiency rating for warm-air, gas or oil-fired furnaces less than 150,000 Btuh. The higher the AFUE, the more efficient the furnace. The minimum percentage established by the Department of Energy (DOE) for furnaces is 78%.

Airflow

The distribution or movement of air.

Air Handler/Coil Blower

The indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your home. An air handler is usually a furnace or a blower coil.

AOH

Annual Operating Hours is the total ration of full- and part-load operating hours in a geographical area.

AHRI

The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) is the trade association representing manufacturers of air conditioning, heating, and commercial refrigeration equipment. An internationally recognized advocate for the industry, AHRI develops standards for and certifies the performance of many of these products. AHRI's 300 member companies account for more than 90 percent of the residential and commercial air conditioning, space heating, water heating and commercial refrigeration equipment manufactured and sold in North America.

Bioaerosols

Microscopic living organisms that grow and multiply in warm, humid places.

Btu

A British thermal unit is a unit 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.

Btuh

British thermal units per hour.

CAE

Combined Annual Efficiency is a measure of the amount of heat produced for every dollar of fuel consumed for both home and water heating.

Capacity

The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTUs; for cooling, in tons.

Carbon Monoxide

An odorless, colorless, tasteless, poisonous and flammable gas that is produced when carbon burns with insufficient air.

Central Air Conditioning System

System in which air is treated at a central location and distributed to and from rooms by one or more fans and a series of ducts.

CFM

Cubic Feet per Minute is a measurement that indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air that is being forced through the ductwork by the system.

Compressor

The part of the outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet cooling requirements.

Condenser Coil

The outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.

Damper

A movable plate, located in the ductwork, that regulates airflow. Dampers are used to direct air to the areas that need it most. Typically used in a zoning application.

dB

A decibel is a unit used to measure the relative intensity of sound.

DOE

The Department of Energy is a United States federal agency responsible for setting industry efficiency standards and monitoring the consumption of energy sources.

Downflow

Air enters at the top of an air handler or furnace and is discharged vertically out the bottom.

Ductwork

A square channel or round tube by which air is distributed from the air handler (e.g.,rooftop unit, furnace, fan coil or VAV box) to the room.

Electronic Air Cleaner

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

ENERGY STAR®

A label attached to HVAC systems that meet or exceed the EPA guidelines for energy efficiency. Applies to products 20 tons and less.

EPA

The Environmental Protection Agency develops and enforces federal environmental regulations for the United States. The EPA oversees the nationwide ENERGY STAR® program.

Evaporator Coil

The part of the air conditioner or heat pump that is located inside the air handler. Its primary function is to absorb the heat from the air.

Fan Coil

A unit that includes a cooling and/or heating coil and a fan to move air through the ductwork to a room. Air filters and accessories to introduce outside ventilation air may also be included.

Heat Exchanger

Transfers heat from one fluid to another without the fluids coming into direct contact with one another.

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 the air ducts. In the summer, it reverses the process and removes heat from the space and releases it outdoors.

Horizontal Flow

Air enters at the end or any side of the unit and is discharged horizontally out the other end or side.

HSPF

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

Humidifier

An indoor air quality device that introduces moisture to heated air as it passes from the furnace into the ductwork for distribution throughout the building.

Humidistat

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

HVAC

Stands for heating, ventilation and air conditioning.

IEER

Integrated Energy Efficiency Ratio expresses cooling part-load EER efficiency for commercial unitary air conditioning and heat pump equipment on the basis of weighted operation at various load capacities.

Indoor Coil

See Evaporator Coil.

IPLC

Integrated Part-Load Capacity is the cooling capacity of the system operating at part-load conditions.

IPLV

Integrated Part-Load Value is the efficiency performance factor at part-load cooling capacity. This performance is critical due to the higher quantity of operating hours under part-load conditions than at full load.

ISO 9000

A family of international standards for quality management and assurance.

LEED

Leadership in Energy and Environmental Design is a green building rating system, with certification indicating a building’s sustainability through high-efficiency and cost savings.

MERV Rating

The Minimum Efficiency Reporting Value rating of a filter describes the size of the holes in the filter that allow air to pass through. The higher the MERV rating, the smaller the holes in the filter and the greater the efficiency.

Micron

A unit of measure equal to one thousandth of a millimeter.

Odors and Chemicals

Air contaminants in the form of gases.

Outdoor Coil

See Condenser Coil.

Particles

Any substances measuring less than 100 microns in diameter. The EPA has found that small particles (less than 2.5 microns) are responsible for some of the most concerning health effects of poor air quality.

Programmable Thermostat

A thermostat with the ability to record different temperature and time settings for your heating and cooling equipment.

R-410A Refrigerant

A chlorine-free refrigerant that meets the EPA's newest, most stringent environmental guidelines.

Refrigerant

A chemical that produces a cooling effect while expanding or vaporizing.

Refrigerant Lines

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

Scroll Compressor

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

SEER

The Seasonal Energy Efficiency Ratio is an energy efficiency rating for air conditioners. The higher the SEER, the better the energy performance and savings. The Department of Energy’s established minimum SEER rating for cooling is 10.00. This rating applies only to equipment 5 tons and under.

Single Package

A heating and cooling system contained in one outdoor unit.

Split System

A combination heat pump or air conditioner with indoor components, such as a furnace or blower coil. Split systems should be matched for optimal efficiency.

Thermidistat

Monitors temperature and humidity and adjusts a heating or cooling system to maintain desired levels.

Thermostat

Usually found on an inside wall, this device controls heating and cooling equipment, allowing simple adjustments of temperature and other comfort control factors, such as humidity and airflow.

Ton

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

Two-Stage Operation

When a unit provides two levels of heat output for greater temperature control.

Upflow

Air handler or furnace configuration in which air enters at the bottom of the unit and is discharged vertically out the top.

USGBC

Stands for U.S. Green Building Council.

Variable-Speed Motor

A variable speed motor provides a quiet, consistent flow of air for enhanced comfort, efficiency and humidity control. According to the Office of Energy Efficiency & Renewable Energy, a variable-speed motor running continuously at a half speed may use up to 75% less power that a single-stage motor uses to move the same amount of air.

Ventilator

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

Zoning

A way to increase comfort and energy efficiency by controlling when and where heating and cooling occurs. Programmable thermostats are used to control operating times of the equipment. Dampers are used to direct air flow to specified zones of a building.