Air Conditioning & Heating Glossary

Important Terms for Homeowners To Know!

  • Air Conditioner -  Equipment that conditions air by cleaning, cooling, heating, humidifying, or dehumidifying it. A term often applied to comfort cooling equipment.
  • Air Handler -  The device that moves the air across the heat exchanger in a forced-air system – normally considered to be the fan and its housing.
  • Air Heat Exchanger -  A device used to exchange heat between air and another medium at different temperature levels, such as air-to-air, air-to-water, or air-to-refrigerant.
  • Air Vent -  A fitting used to vent air manually or automatically from a system.
  • B-vent -  A venting system for gas stoves or other gas appliances using approved piping through the roof or into a chimney.
  • Bearing -  A device that surrounds a rotating shaft and provides a low-friction contact surface to reduce wear from the rotating shaft
  • Bleed Valve -  A valve with a small port usually used to bleed pressure from a vessel to the atmosphere.
  • Bleeding -  Allowing pressure to move from one pressure level to another very slowly.
  • Breaker -  Heat-activated electrical device used to open an electrical circuit to protect it from excessive current flow.
  • BTU -  Abbreviation for British thermal unit: the amount (quantity) of heat required to raise the temperature of 1lb of water 1 degree F.
  • Capacitor -  An electrical storage device used to start motors (start capacitor) and to improve the efficiency of motors (run capacitor).
  • Charge Refrigerant -  The quantity of refrigerant in a system.
  • Charging Scale -  A scale used to weigh refrigerant when charging a refrigeration or air conditioning system.
  • Check Valve -  A device that permits fluid flow in one direction only.
  • Circuit -  An electron or fluid-flow path that makes a complete loop.
  • Circuit Breaker -  A device that opens an electric circuit when an overload occurs.
  • Compressor -  A vapor pump that pumps vapor (refrigerant or air) from one pressure level to a higher pressure level.
  • Condensing Unit -  A complete unit that includes the compressor and the condensing coil.
  • Contactor -  A larger version of the relay. It can be repaired or rebuilt and has moveable and stationary contacts.
  • Defrost Cycle -  The portion of the refrigeration cycle that melts the ice off the evaporator.
  • Differential -  The difference in the cut-in and cut-out points of a control, pressure, time, temperature or level.
  • Drier -  A device used in a refrigerant line to remove moisture.
  • Drip pan -  A pan shaped to collect moisture condensing on an evaporator coil in an air conditioning or refrigeration system.
  • Duct -  A sealed channel used to convey air from the system to and from the point of utilization.
  • Electronic Leak Detector -  An instrument used to detect gases in very small portions by using electronic sensors and circuits.
  • EPA -  Abbreviation for the Environmental Protection Agency
  • Evaporator -  The component in a refrigeration system that absorbs heat into the system and evaporates the liquid refrigerant.
  • Fan Cycling -  The use of a pressure control to turn a condenser fan on and off to maintain a correct pressure within the system
  • Freeze Up -  Excess ice or frost accumulation on a evaporator to the point that airflow may be affected.
  • Freon -  The name for refrigerants manufactured.
  • Furnace -  Equipment used to convert heating energy such as fuel oil, gas or electricity to usable heat. It usually contains a heat exchanger, a blower, and controls to operate the system.
  • Fuse -  A safety device used in electrical circuits for the protection of the circuit conductor and components.
  • Gage -  An instrument used to indicate pressure.
  • Gas valve -  A value used to stop, start, or modulate the flow of natural gas.
  • Heat -  Energy that causes molecules to be in motion and to raise the temperature of a substance.
  • Heat Coil -  A device made of tubing or pipe designed to transfer heat to a cooler substance by using fluids.
  • Heat Pump -  A refrigeration system used to supply heat or cooling using valves to reverse the refrigerant gas flow.
  • Hot Gas Line -  The tubing between the compressor and condenser.
  • Hot Surface Ignition -  A silicon carbide or similar substance is placed in gas stream of a gas furnace and allowed to get very hot. When the gas impinges on this surface, immediate ignition should occur.
  • Hydronic -  Usually refers to a hot water heating system
  • Ignition Transformer -  Provides a high-voltage current, usually to produce a spark to ignite a furnace fuel, either gas or oil.
  • King Valve -  A service valve at the liquid receiver's outlet in a refrigeration system.
  • Leak Detector -  Any device used to detect leaks in a pressurized system.
  • Limit Control -  A control used to make a change in a system, usually to stop it when predetermined limits of pressure or temperature are reached.
  • Liquid Line -  A term applied in the industry to refer to the tubing or piping from the condenser to the expansion device.
Reference: Refrigeration and Air Conditioning Technology, 4th Edition, Whitman/Johnson/Tomczyk