Glossary

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There are currently 61 names in this directory
A-Coil
A heat exchanger containing two diagonal coils that are connected together in a manner that resembles the letter “A."

AFUE
Annual Fuel Utilization Efficiency. A measure of a gas furnace’s efficiency in converting fuel to energy. The higher the rating, the more efficient the unit. The unit is more efficient when the rating is higher.

AGA
Abbreviation for American Gas Association, Inc.

BTU
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).

BTUh
British thermal units per hour. 12,000 BTUh equals one ton of cooling.

Burner
An instrument that uses fuel to support combustion.

Burner (sealed combustion)
A burner that acquires all air for combustion from outside the heated space.

Capacity
The ability of a heating or cooling system to cool or heat a given amount of space. For heating, this is usually expressed in BTU’s. For cooling, it is often given in tons.

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).

Charge
Adding refrigerant to a system. Refrigerant is contained in a sealed system or in the sensing bulb to a thermostatic expansion valve.

Condensate
Vapor that liquefies due to the lowering of its temperature to the saturation point.

Contactor
A switch that can repeatedly cycle, making and breaking an electrical circuit. When ample current flows through the A-coil which is built into the contactor, the resulting magnetic field causes the contacts to be pulled in or closed.

Crankcase Heater
This is the electric resistance heater installed on compressor crankcases to keep the crankcase oil at a temperature higher than the coldest part of the system to prevent migration. Many newer cooling systems do not require crankcase heaters. However, heat pumps do require crankcase heaters. Crankcase heaters are used to overcome the problem of migration and condensation of refrigerant in the crankcases of compressors used in air conditioning and heat pump systems.

CSA
Canadian Standards Association.

Defrost
The process of removing ice or frost buildup from the outdoor coil during the heating season.

Degree Day
A computation that measures the amount of heating or cooling needed for a building. A degree day is equal to 65 degrees Fahrenheit minus the mean outdoor temperature.

DOE
Department of Energy

Downflow Furnace
A furnace that pulls in return-air from the top and discharges warm air at the bottom.

Drain Pan
Also referred to as a condensate pan. This is a pan used to catch and collect condensate (in residential systems, vapor is liquefied on the indoor coil, collected in the drain pan, and removed through a drain line).

Dry Bulb Temperature
Heat intensity, measured by a dry bulb thermometer.

DX
Direct expansion. A system in which heat is passed on by the direct expansion of refrigerant.

EPA
Environmental Protection Agency. ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy helping us all save money and protect the environment through energy efficient products and practices.

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). This is the most commonly used scale of temperature measurement in the United States of America.

Flue
Any vent or duct, pipe, or chimney for carrying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors.

Furnace
That part of an environmental system which converts gas, oil, electricity or other fuel into heat for distribution within a structure.

Fuse
A fuse is a type of overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which breaks the circuit in which it is connected, thus protecting the circuit’s other components from damage due to excessive current.

GAMA
Gas Appliance Manufacturers Association.

Gas Furnace Heat Exchanger
Found in the furnace, the heat exchanger transfers heat to the surrounding air which is then transported throughout your home.

Heat Exchanger
An area, box, or coil where heat flows from the warmer to the colder fluid or surface. A device for the transfer of heat energy from the source to the conveying medium.

Heat Gain
The amount of heat introduced to a space from all heat producing sources by appliances, solar energy, occupant respiration, and lighting.

Heat Loss
The rate of heat transfer from a building interior to the outdoors.

Heat Pump
An automated compression cycle refrigeration system that can be switched to either heat or cool the controlled space.

Heat Transfer
The movement of heat energy from one area to another. The means for such movement are convection, conduction, and radiation. Heat will flow naturally from a warmer to a cooler space or material.

Heating Coil
Any coil that serves as a heat source.

Hertz
A measure of the number of cycles or wavelengths of electrical energy per second; U.S. electricity supply has a standard frequency of 60 hertz.

HSPF
Heating Seasonal Performance Factor. This rating is used in measuring the heating efficiency of a heat pump by taking into account the variations in temperature that can occur within a season and is the average number of BTUs of heat dispatched for every watt-hour of electricity used by the heat pump over a heating season. The higher the number, the more efficient the heat pump system.

Ignition
The lighting of a gaseous mixture to the temperature at which combustion takes place.

Kilowatt (kW)
1,000 watts. A common unit of electrical consumption measured by the total energy created by one kilowatt in one hour.

Latent Heat
A type of heat which, when added to or taken from a substance, does not change the temperature of the substance yet enables the heat energy to change its state.

OEM
Original equipment manufacturer.

Package Unit
A heating and cooling system contained in one outdoor cabinet. This package unit is typically installed on the roof or beside or sometimes in the attic of a home.

PSI
Pounds per square inch.

PSIA
Pounds per square inch, absolute.

PSIG
Pounds per square inch gauge.

PVC
Polyvinyl chloride; a type of plastic. In recent years, PVC has been replacing traditional building materials such as wood, concrete, and clay in many areas.

Reciprocating Compressor
A compressor that uses pistons driven by a crankshaft to deliver gases at high pressure.

Sensible Heat
That heat which, when added to or taken away from a substance, causes a change in temperature.

Sensor
Any device that responds to a change in the conditions being measured, permitting the condition to be controlled.

Setpoint
The temperature or pressure at which a controller is set for desired comfort level.

Spine Fin™ Coil
All aluminum outdoor coils that feature the patented Spine Fin design. Spine Fin consists of thousands of tiny spines bonded to continuous aluminum refrigerant tubing. The tiny spines create a greater surface area, helping it to transfer more heat from your home, more efficiently. It provides greater heat exchanging capabilities (meaning higher efficiencies) and is more resistant to corrosion than traditional copper/aluminum.

Split System
The combination of an outdoor unit (air conditioner or heat pump) with an indoor unit (furnace or air handler). Split systems must be paired for optimal efficiency. This is the most common type of system installed in a home.

Thermostat
A series of sensors and relays that monitor and control the functions of a heating and cooling system by turning the device on or off when a specified temperature is reached.

Thermostatic Expansion Valve
A thermostatic expansion valve (TXV) is precision device used to meter the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator. Also called a thermal expansion valve.

Ton
A unit of measurement used for determining the cooling capacity of a system. One ton of cooling is based on the amount of heat needed to melt one ton (2000 lbs.) of ice in a 24 hour period. One ton of cooling is equal to 12,000 BTU/hr.

Two-Stage Heating
The furnace has two stages of heat output: high for cold winter days and low for milder days. Since the low setting is adequate to meet household-cooling demands 80% of the time, a two-stage unit runs for extended periods and delivers more uniform heat distribution.

U-Factor
The factor amounting to the resistance of heat flow through various building materials.

UL
Underwriters Laboratories.

Upflow Furnace
A furnace in which air is drawn in through the bottom or sides and expels warm air out the top.

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

Variable speed motor(s)
The fan motor inside Trane’s variable speed air handlers is designed to vary its speed based on your home’s heating and air conditioning requirements. Working in conjunction with the thermostat, it keeps the appropriate temperature air (e.g. warm air on cold days) circulating throughout your home, reducing temperature variances in your home. It also provides greater air circulation and filtration, better temperature distribution and humidity control, higher efficiency, and quiet performance.

Wet Bulb Thermometer
A thermometer whose bulb is covered with a piece of water-soaked cloth. It is a type of temperature measurement that reflects the physical properties of a system with a mixture of a gas and a vapor, usually air and water vapor.