Industry Terminology


A – Coil
This heat exchanger depends on two coils, placed diagonally and then connected in the middle. The result is a coil that looks like the letter “A”.

This electric current rapidly changes its direction of flow. See also DC (Direct Current).

AC or DC
These abbreviations stand for Alternating Current and Direct Current, and represent forms of electrical circuiting.

Air Conditioning Contractors of America.

A derivative of the word “acoustic”. When a system is acoustical, it makes or conducts sound well.

This yearly measurement is an efficiency test of the conversion of fuel to energy by a furnace. A high rating on an AFUE test indicates a good furnace. Service Champions technicians can do AFUE tests.

Abbreviation for American Gas Association, Inc.

Air Cleaner
Also known as an air filter, this equipment removes dust, debris, and other particles floating in the air. When air moves through the air cleaner, these particles are caught.

Air Conditioner
This system is usually placed outside the home, and controls the humidity, ventilation, and temperature of the air inside.

Air Flow Volume
This is a measurement of an air conditioner’s output. Airflow volume is calculated by measuring the cubic feet per minute that the air conditioner circulates.

Air Handler
This piece of the air conditioning system regulates and directs air throughout the ductwork, spreading heated or cooled air through the home.

Air Conditioning & Refrigeration Institute.

American Society of Heating, Refrigeration and Air Conditioning Engineer


British thermal unit. The standard of measurement used to gauge the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit).

Equal to about 1.06 kilojoules, this measurement is taken in heating and cooling when assessing the power output of an air conditioner or furnace. BTU measurement can also be taken by the hour, and are known as BTUh.

This piece of a furnace conducts heat using electric or gas fuel.

Burner (sealed combustion)
A piece of a furnace that conducts heat using the air outside of the system.

Burner Orifice
The piece of the burner that inputs gas. The gas is then mixed with air and used as fuel.


The capability of a heating or cooling system to fill a required space.

The metric scale of temperature. When measured on water, the freezing point is 0˚C, and the boiling point is 100˚C. Conversion from Celsius to Fahrenheit is as follows.
Multiply by 9, then divide by 5, then add 32

CFM – (Cubic Feet per Minute)
The airflow rate in an air conditioning system.

The process of adding refrigerant to an air conditioning system. Refrigerant is stored in a sealed system and aids in the overall cooling factor. Refrigerant moves from the indoor evaporator to the outdoor condenser and then back to the indoor evaporator.

The piece of equipment pumps refrigerant through a sealed system.

The process of a chemical that changes from its vapor form to its liquid form.

Condenser coil (or outdoor coil)
Also known as an outdoor coil. This piece of the air conditioner removes heat from refrigerant in vapor form. When the heat is removed, the refrigerant becomes liquid and moves back to the inside of the machine.

Condenser Fan
This piece of equipment cools the condenser by blowing air on it.

This piece of equipment cycles electrical current. A contactor switches on and off; connecting and breaking an electrical current.

Crankcase Heater
A piece of equipment that maintains the vapor form of refrigerant in the crankcase part of the system. By heating the crankcase oil to a higher temperature than the coldest part of the system, refrigerant remains in its vapor form.


A plate that opens and closes to regulate air flow through the ductwork system.

DC – (Direct Current)
This electric current travels in a direct route. See also AC (Alternating Current).

The process in which removes frost buildup from the outdoor coil. This usually takes place when the weather is cold and the air conditioner is not in use.

Measurement of required for an amount of space. It is equal to the outside temperature minus 65˚F.

This piece of equipment extracts humidity from the air. It cools air to the point where water turns from vapor to liquid form and then removes the liquid.

Placed over ductwork, this part separates air with vanes going in differing directions.

Department of Energy

Downflow Furnace
This type of furnace processes air from top to bottom.

Drain Pan
This part catches any condensate left in the machine. Not all machines need a drain pan.

Dry Bulb Temperature
A measurement of heat intensity independently of humidity. A dry bulb thermometer takes this measurement.

Dry Bulb Thermometer
An device that measures air temperature independently of humidity.

This system of pipes transports heat from the central air conditioning or heating system to the rest of the building.

This refers to the expansion of refrigerant. This process conducts heat.


This is a measurement of the cooling capacity of an air conditioner.
BTUh: electrical watt input.

This Federal Agency encourages the use of eco – friendly, non –pollutant, and energy efficient equipment in every sector, including heating and air conditioning.

Evaporator Coil (or Indoor Coil)
Also known as the indoor coil, this piece of equipment removes heat and humidity from the air inside the building.

Expansion Valve
This part measures the pressure and temperature of refrigerant.


This temperature scale is used mostly in the United States. When measured in water, the freezing point is 32˚F and the boiling point is 212˚F. Conversion to the Celsius temperature scale, use the equation below:
Deduct 32, then multiply by 5, then divide by 9

This piece of equipment uses motion to create an air current.

This part removes particles of dust and other debris from the air. (See MERV Rating).

This part of the equipment vents out exhaust gases.

This heating system uses fuel to produce heat for a building.

This part protects against overcurrent. When too much electricity is running, the fuse melts and breaks the current.


Gas Appliance Manufacturers Association.

Gas Furnace Heat Exchanger
This part of the system moves heat from inside the furnace into the air outside the furnace. The duct system transfers this air to rooms in the building.


Heat Exchanger
The part of the system allows heat to be transferred from the hot parts of the machine to the cold parts of the machine.

Heat Gain
This is a total amount of heat an area receives from all heat conducting machines including furnaces, appliances, lighting, respiration and solar energy.

Heat Loss
This is a measurement of the rate heat escapes from the inside of a building to the outside of the building.

Heat Pump
This compressor cycles hot or cold air to the building.

Heat Transfer
The process where heat moves from one area to another.

Heating Coil
This part of the system conducts heat.

The measurement of electrical energy per second. Standard frequency is 6- Hertz.

HSPF – (Heating Seasonal Performance Factor)
The measurement of heat efficiency over the period of a heating season.

The sensor which measures and regulates humidity.

The sensor which measures and regulates humidity.

The measurement of moisture volume in the air.

Humidity, Absolute
The ratio of humidity between saturated and non – saturated air. It is taken by measuring the grams of water vapor in 1 cubic meter of air.

Humidity, Relative
The ratio of current humidity to the humidity if the air were 100% saturated.

HVAC – (Heating, Ventilating and Air Conditioning)


Beginning of the combustion process, ignition requires a gaseous mixture to take flame form.


Kilowatt (kW)
The electrical measurement of 1,000 watts.


Latent Heat
The type of heat that controlled the state of a substance rather than the temperature.


The part of an air filter which traps dust particles, debris and other impurities in the air. This can be made of fiberglass, polyester, dog hair, blue/green, and charcoal, among other materials.

MERV rating (Minimum Efficiency Reporting Value)
Numbered from 1 to 16, this measurement gives the efficiency value of an air filter.


NEC - (National Energy Council / National Electric Code)

NEMA – (National Electrical Manufacturing Association)


OEM – (Original Equipment manufacturer)


Package Unit
This smaller heating or cooling unit is used for residential purposes and is usually located on the roof or in the attic of a house. It can be moved without disconnecting any refrigerant lines.

PSI – (Pounds per square inch)

PSIA – (Pounds per square inch, absolute)
Pounds per square inch, absolute.

PSIG – (Pounds per square inch gauge)</strong?

PVC – (Polyvinyl chloride)
This plastic is used more frequently in buildings.


Reciprocating Compressor
This piece of equipment work directly with the crankshaft to highly pressurizes gases.

The chemical used to cool air. It expands to vapor form, gathering hot air, and then contracts to liquid form to cool the air.

Refrigerant Charge
The required amount of refrigerant in a system.


The measurement of seasonal or annual heating or cooling efficiency. This rating is used nation – wide and is a good indicator of operating cost.

Self Contained System
(See Package Unit)

Sensible Heat
The type of heat the affects the temperature of a substance.

The piece of equipment that measures and regulates changes. Air conditioning and heating sensors measure the air temperature and humidity among other things.

Part of the thermostat, this is the indicator of the desired indoor temperature.

Spine Fin™ Coil
The aluminum outdoor coil made of tiny spines. This creates a greater surface area, which improves heat exchange efficiency. This technology is patented.

Split System
The combination of an outdoor unit and an indoor unit. This is the most common type of system.


This system monitors and regulates a heating or cooling system.

The measurement of the cooling capacity of a heating or cooling system. A ton of energy can melt a ton of ice in a 24-hour period.

Two-stage (cooling and heating)
An air conditioner designed to operate on high and low settings during different weather. The high setting is used during more extreme weather, and the low setting is used during more moderate weather. This type of air conditioner is in use for a longer period of time, and produces a balanced temperature.

TXV – Thermostatic Expansion Valve
The piece of equipment that meters the flow of liquid refrigerant into the evaporator while also measuring the vapor refrigerant leaving the evaporator


This refers to the resistance of heat flow through building materials

UL – Underwriters Laboratories

Upflow Furnace
A furnace that operates air from bottom to top.


A pressure below atmospheric pressure. 30 inches Mercury (periodic symbol “Hg”) is a perfect vacuum.

Variable speed motor(s)
A type of fan that adjust speed according to the need of operation. This contributes to efficiency and performance of the machine.

Measurement of electrical force given to the electrons in an electric circuit.

The force that pushes electrical current along wires and cables.


A unit of electrical power. It is equal to the flow of one amp at a potential difference of one volt, and does the same amount of work as 1 joule.

Wet Bulb Thermometer
A sensor that measures gas and vapor in the air using a bulb covered in a water soaked cloth.


Zoning System
This system sections a building into zones that can be controlled independently of each other.