Glossary of Terms

AFUE - Annual Fuel Utilization Efficiency applies to furnaces - both gas and oil. It describes the percentage of heat produced for every dollar of fuel consumed.
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Air Conditioner - Equipment that conditions air by cleaning, cooling, heating, humidifying, or dehumidifying it. A term often applied to comfort cooling equipment.
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Air Conditioning - A process that maintains comfort conditions in a defined area.
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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.
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Air sensor - A device that registers changes in air conditions such as pressure, velocity, temperature, or moisture content.
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Air vent - A fitting used to vent air manually or automatically from a system.
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Automatic control - Controls that react to a change in conditions to cause the condition to stabilize.
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Automatic expansion valve - A refrigerant control valve that maintains a constant pressure in an evaporator.
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Bleeding - Allowing pressure to move from one pressure level to another very slowly.
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Bore - The inside diameter of a cylinder.
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British thermal unit - The amount (quantity) of heat required to raise the temperature of 1lb of water 1'F.
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Btu - Abbreviation for British thermal unit.
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Burner - A device used to prepare and burn fuel.
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Carbon dioxide - A byproduct of natural gas combustion that is not harmful.
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Carbon monoxide - A poisonous, colorless, odorless, tasteless gas generated by incomplete combustion.
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Charge - The quantity of refrigerant in a system. Charging cylinder: A device that allows the technician to accurately charge a refrigeration system with refrigerant.
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Chlorofluocarbons (CFC) - Those refrigerants thought to contribute to the depletion of the ozone layer.
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Circuit breaker - A device that opens an electric circuit when an overload occurs.
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CO2 indicator - An instrument used to detect the quantity of carbon dioxide in flue gas for efficiency purposes.
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Code - The local, state, or national rules that govern safe installation and service of systems and equipment for the purpose of safety of the public and trade personnel.
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Cold - The word used to describe heat at lower levels of intensity.
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Combustion - A reaction called rapid oxidation or burning produced with the right combination of a fuel, oxygen, and heat.
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Compressor - A vapor pump that pumps vapor (refrigerant or air) from one pressure level to a higher pressure level.
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Condensate - The moisture collected on an evaporator coil.
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Condensate pump - A small pump used to pump condensate to a higher level.
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Condenser - The component in a refrigeration system than transfers heat from the system by condensing refrigerant.
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Condensing temperature - The temperature at which a vapor changes to a liquid.
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Condensing unit - A complete unit that includes the compressor and the condensing coil.
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Cycle - A complete sequence of events (from start to finish) in a system.
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Damper - A component in an air distribution system that restricts air flow from the purpose of air balance.
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Dehumidify - To remove moisture from air.
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Density - The weight per unit of volume of a substance.
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Dew point - The exact temperature at which moisture begins to form.
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Drier - A device used in a refrigerant line to remove moisture.
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Drip pan - A pan shaped to collect moisture condensing on an evaporator coil in an air conditioning of refrigeration system.
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Duct - A sealed channel used to convey air from the system to and from the point of utilization.
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Electronic air filter - A filter that changes dust particles using high-voltage direct current and then collects these particles on a plate of an opposite charge.
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Energy Efficiency Ratio (EER) - An equipment efficiency rating that is determined by dividing the output in BTU by input in watts. This does not take into account the startup and shutdown for each cycle.
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Energy Recovery Ventilator - Brings fresh outside air into an indoor environment and exchanges it with stale indoor air. A transfer core allows heat and humidity to be transferred from the outgoing air to the incoming air.
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Ethane gas - The fossil fuel, natural gas, used for heat.
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Evaporation - The condition that occurs when heat is absorbed by liquid and it changes to vapor.
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Fahrenheit scale - The temperature scale that places the boiling point of water at 212'F and the freezing point at 32'F.
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Fan - A device that produces a pressure difference in air to move it.
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Fan cycling - The used of a pressure control to turn a condenser fan on and off to maintain a correct pressure within the system.
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Fan relay coil - A magnetic coil that controls the starting and stopping of a fan.
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Filter - A fine mesh or porous material that removes particles from passing fluids.
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Flue - The duct that carries the products of combustion out of a structure for a fossil-or-solid fuel system.
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Fluid - The state of matter of liquids and gases.
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Flush - The process of using a fluid to push contaminants from a system.
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Force - Energy exerted.
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Freeze up - Excess ice or frost accumulation on an evaporator to the point that airflow may be affected.
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Freon - The trade name for refrigerants manufactured by E.I. duPont de Nemours & Co.,Inc.
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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 the controls to operate the system.
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Gage - An instrument used to detect pressure.
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Gas - The vapor state of matter.
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Gas valve - A valve used to stop, start, or modulate the flow of natural gas.
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Heat - Energy that causes molecules to be in motion and to raise the temperature of a substance.
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Heat anticipator - A device that anticipates the need for cutting off the heating system prematurely so the fan can cool the furnace.
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Heat coil - A device made of tubing or pipe designed to transfer heat to a cooler substance by using fluids.
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Heat exchanger - A device that transfers heat from one substance to another.
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Heat pump - A refrigeration system used to supply heat or cooling using valves to reverse the refrigerant gas flow.
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Heat Recovery Ventilator - Brings fresh outside air into an indoor environment and exchanges it with stale indoor air. A transfer core allows heat to be transferred from the outgoing air to the incoming air.
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HEPA filtration - High Efficiency Particulate Arresting filters can remove up to 99.97% of particulates 0.3 microns and larger. Highest of all filtration products.
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Humidifier - A device used to add moisture to the air.
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Hydrochlorofluorocarbons (HCFC) - Refrigerants thought to contribute to the depletion of the ozone layer although not to the extent of chlorofluorocarbons.
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ICM motor - Is a variable-speed motor. It adjusts its speed to deliver the right airflow needed by the system.
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Ignition transformer - Provides a high-voltage current, usually to produce a spark to ignite a furnace fuel, either gas or oil.
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Induced draft motor - The draft developed in the heat exchanger of a gas-fired furnace by a fan located at the outlet of the heat exchanger, May be used with a natural-draft vent, or with a direct vent system: also called fan-assisted or mechanical draft.
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Inert gas - A gas that will not support most chemical reactions, particularly oxidation.
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Intermittent ignition - Ignition system for a gas furnace that operates only when needed or when furnace is operating.
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Junction box - A metal or plastic box within which electrical connections are made.
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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.
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Line set - A term used for tubing sets furnished by the manufacturer.
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Liquid - A substance where molecules push outward and downward and seek a uniform level.
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Liquid line - A term applied in the industry to refer to the tubing or piping from the condenser to the expansion device.
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Liquid receiver - A container in the refrigeration system where liquid refrigerant is stored.
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Melting point - The temperature at which a substance will change from a solid to a liquid.
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Modulator - A device that adjusts by small increments of changes.
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Molecule - The smallest particle that a substance can be broken into and still retain its chemical identity.
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Montreal Protocol - This landmark agreement initially required a production and consumption freeze. The Montreal Protocol called for a stepwise reduction and eventual production phase-out of various ozone depleting substances in developed countries.
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Natural gas - A fossil fuel formed over millions of years from dead vegetation and animals that were deposited or washed deep into the earth.
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Neutralizer - A substance used to counteract acids.
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Nitrogen - An inert gas often used to "sweep" a refrigeration system to help ensure that all refrigerant and contaminants have been removed.
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Oxidation - The combining of a material with oxygen to form a different substance. This results in the deterioration of the original substance.
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Ozone - A form of oxygen. A layer of ozone in the stratosphere that protects the earth from certain of the sun's ultraviolet wave lengths.
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Package unit - A refrigeration system where all major components are located in one cabinet.
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Pilot light - The flame that ignites the main burner on a gas furnace.
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Plenum - A sealed chamber at the inlet or outlet of an air handler. The duct attaches to the plenum.
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Pressure - Force per unit of area.
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Pressure limiter - A device that opens when a certain pressure is reached.
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Pressure switch - A switch operated by a change in pressure.
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Propane - An LP gas used for heat.
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PSI - Abbreviation for pounds per square inch.
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Pump - A device that forces fluids through a system.
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Purge - To remove or release fluid from a system.
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PVC ( Polyvinyl choride) - Plastic pipe used in pressure applications for water and gas as well as for sewage and certain industrial applications.
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R-22 - Monochlorodifluoromethane, a popular refrigerant for air conditioning systems.
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Refrigerant - The fluid in a refrigeration system that changes from a liquid to a vapor and back to a liquid at practical pressures.
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Refrigerant recovery - To remove refrigerant in any condition from a system and store it in an external container without necessary testing of processing it in any way.
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Refrigerant recycling - To clean the refrigerant by oil separation and single or multiple passes through devices, such as replaceable core filter-driers, which reduce moisture, acidity and particulate matter. This term usually applies to procedures implemented at the job site or at a local service shop.
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Refrigeration - The process of removing heat from a place where it is not wanted and transferring heat to a place where it makes little or no difference.
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Relay - A small electromagnetic device to control a switch, motor, or valve.
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Relief valve - A valve designed to open and release liquids at a certain pressure.
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Rollout switch - A heat-sensitive protective device that opens the circuit if flame migrates away from the burner box.
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Rotor - The rotating or moving component of a motor, including the shaft.
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Scroll compressor - A compressor that uses two scroll-type components to compress vapor.
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Seasonal energy efficiency ratio (SEER) - An equipment efficiency rating that takes into account the startup and shutdown for each cycle.
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Sensor - A component for detection that changes shape, form, or resistance when a condition changes.
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Service valve - A manually operated valve in a refrigeration system used for various service procedures.
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Short cycle - The term used to describe the running time (on time) of a unit when it is not running long enough.
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Solenoid - A coil of wire designed to carry an electrical current producing a magnetic field.
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Split system - A refrigeration or air conditioning system that has the condensing unit remote from the indoor (evaporator) coil.
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Steam - The vapor state of water.
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Subcooling - The temperature of a liquid when it is cooled below its condensing temperature.
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Temperature - A word used to describe the level of heat of molecular activity.
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Thermocoupler - A device made of two unlike metals that generates electricity when there is a difference in temperature from one end to the other. Thermocouples have a hot and cold junction.
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Thermometer - An instrument used to detect differences in the level of heat.
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Thermostat - A device that senses temperature change and changes some dimension or condition within to control an operating device.
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Thermostatic expansion valve (TXV) - A valve used in refrigeration systems to control the superheat in an evaporator by metering the correct refrigerant flow to the evaporator.
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Ton of refrigeration - The amount of heat required to melt a ton (2000 lb) of ice at 32'F, 288,000 Btu/24 h, 12,000 Btu/h, or 200 Btu/min.
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Transformer - A coil or wire wrapped around an iron core that induces a current to another coil of wire wrapped around the same iron core.
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Ultraviolet - Light waves that can only be seen under a special lamp.
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Vacuum pump - A pump used to remove some fluids such as air and moisture from a system at a pressure below the earth's atmosphere.
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Valve - A device used to control fluid flow.
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Vapor - The gaseous state of a substance.
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Vapor lock - A condition where vapor is trapped in a liquid line and impedes liquid flow.
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Vapor pump - Another name for compressor.
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Vaporization - The changing of a liquid to a gas or vapor.
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Velocity - The speed at which a substance passes a point.
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Watt - A unit of power applied to electron flow. One watt equals 3.414 Btu.
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