AC
Abbreviation for alternating current, a type of electric current in which the polarity is constantly reversing causing the electron flow to reverse.

AC or DC
Abbreviation for equipment capable of operating on alternating or direct current.

A-Coil
A heat exchanger consisting of two diagonal coils that are joined together in a manner that looks like the letter “A”.

AFUE
Stands for Annual Fuel Utilization Efficiency. This number represents how efficiently a furnace converts fuel to energy. The higher the rating, the more fuel-efficient the furnace is.Percentage of fuel used for heating.

Air Conditioner
Any device that can change the temperature, humidity or general quality of the air.

Air cleaner
Any device that removes undesirable particles from moving air.

Air flow volume
The amount of air the system circulates through your home, expressed in cubic feet per minute (cfm). Proper air flow depends on the outdoor unit, the indoor unit, the ductwork and even whether the filters are clean.

Air Handler
The portion of your air conditioner or heating system that forces air through your home’s ductwork.

BTU
Stands for British Thermal Units. This number indicates the amount of heat it takes to raise one pound of water one degree Fahrenheit. The higher the BTU rating, the larger the heating capacity of the furnace or air conditioner. Homes are measured to determine the number of BTUs required from a heating or cooling system.

Carbon Monoxide
A colorless, odorless, highly poisonous gas produced when carbon burns without sufficient air nearby.

Celsius
The metric temperature scale in which water freezes at zero degrees and boils at 100 degrees, designated by the symbol “C”. To convert to Fahrenheit, multiply a Celsius temperature by 9, divide by 5 and add 32 (25 x 9 equals 225, divided by 5 equals 45, plus 32 equals 77 degrees Fahrenheit).

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

Charge To add refrigerant to a system
This is refrigerant contained in a sealed system or in the sensing bulb to a thermostatic expansion valve.

Compressor
The Compressor is the most important piece of a heating or cooling system. Located in the outdoor unit, the compressor is responsible for pumping refrigerant throughout the system.

Condenser Coil
The outdoor portion of a heating or cooling system that either releases or collects heat from the outside air, depending on the time of year. The Condenser Coil is connected directly to the home’s Air Handler and is also known as the Outdoor Coil.

Damper
A movable plate that controls airflow through a ductwork system. Dampers are used to direct air to the areas of the home that need it most.

DC
Direct current electricity. This type of electricity (as opposed to Alternating Current, or AC) flows in one direction only, without reversing polarity.

Dehumidifier
An air cooler that removes moisture from the air.

Diffuser
A grille over an air supply duct having vanes to distribute the discharging air in a specific pattern or direction.

Ductwork
Hollow pipes used to transfer air from the Air Handler to the air vents throughout your home. Ductwork is one of the most important components of a home heating and cooling system.

Evaporator Coil
This is where refrigerant evaporates as it removes heat from the air that is passed over it. The Evaporator Coil is located in the indoor unit and is also referred to as the Indoor Coil.

Fahrenheit
The temperature scale on which water freezes at 32 degrees and boils at 212 degrees; designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5 and divide by 9 (77 -32 equals 45, times 5 equals 225, divided by 9 equals 25 degrees Celsius).

Fan
Any device that creates air currents.

Filter
Any device that removes impurities through a straining process.

Flue
Any vent or passageway that carries the products of combustion from a furnace.

Furnace
That part of the heating system in which the combustion of fossil fuel and transfer of heat occurs.

Fuse
A metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it. The fuse is designed to break in order to save more expensive electrical components.

Heat Exchanger
The part of a furnace that transfers heat to nearby air. That air is then distributed through the Ductwork throughout your home.
Heat Pump A heating and air conditioning unit that heats or cools by moving heat.

HSPF
Stands for Heating Seasonal Performance Factor. Indicates how efficiently a Heat Pump is working. A higher number means the unit works more efficiently. Most new units have ratings from 7.0 to 9.4.

Humidifier
A component that adds moisture to the air before it is distributed by the Ductwork throughout the house.

HVAC
Stands for Heating, Ventilation, and Air Conditioning.

Refrigerant
A chemical that cools air as it evaporates. Air conditioning systems use Refrigerant in the Evaporator Coil to cool air as it passes by.

Refrigerant Lines
Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil.

SEER
Stands for Seasonal Energy Efficiency Ratio. An efficiency measurement that is similar to Miles Per Gallon for cars. The higher this number, the more energy efficient they system is. New units have SEER ratings from 10 to 17 BTUs per watt.

Single Package
One outdoor unit that contains both a heating and a cooling system.

Split System
A combination heat pump or air conditioner with indoor components such as a furnace or blower coil. To maximize effectiveness, Split Systems should be matched.

Thermostat
A device that allows you to control the temperature inside your home by telling the heating or cooling system how much air to produce.

Zoning
The dividing of a home into different areas each with their own heating and cooling properties. For example, you might prefer to have the kitchen area of your home be slightly cool, while at the same time keeping the temperature in the bedrooms warmer.