Browse Index (choose letter below) Use Caution! These entries are hyperlinked to the definitions! Certain states require the use of protective goggles for the viewing of hyperlinked data. 

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A-Coil Alternating Current AFUE AGA Air Conditioner Air Flow Volume Air Handler ARI ASHRAE BTU BTUh Burner Burner Orifice Capacity Celsius Centigrade CFM Charging a System Compressor Condensate	Condensate Pump Condensor CSA Direct Current Damper Degree-Day Dehumidifier Downflow Furnace Drain Pan Dry Bulb Temperature Ductwork EPA Expansion Valve Evaporator Coil Fahrenheit Fan Filter Flue Furnace	Fuse GAMA Heat Exchanger Heat Loss Heat Pump Heat Transfer Humidifier Humidistat Humidity HVAC Ignition Kilowatt Latent Heat Media NEC NEMA Orifice plenum PSI PVC	Reciprocating Compressor Refrigerant Refrigerant Charge SEER Sensor Split System Thermostat Thermostatic Expansion Valve Ton TXV Upflow Furnace Vacuum Volt Watt Wet Bulb Thermometer Zone

	a-coil	also known as the "evaporator coil" of an air conditioning system. A radiator-like device inside the sheet metal box above a furnace with central air conditioning.  There are usually two flat radiating surfaces, fastened over the furnace, joined at the top, approximately shaped like the letter "A" (hence the name). The outdoor condensor delivers cool refrigerant to the tubes making up the a-coil.  House air is passed through the radiating fins of the a-coil, which transfers the cooling to the air passing through the furnace. see also "evaporator coil"
	alternating current	Also referred to as "AC" - A type of electric current where the polarity is reversed (usually) at the rate of 60 times per second.  In the USA, most household current is 60-cycle alternating current.
	AFUE	Annual Fuel Utilization Efficiency. A percentage measurement used to rate furnace efficiencies by dividing the ratio of heat output by heat input.
	AGA	American Gas Association, Inc., an independent testing organization, supplies standard ratings for home heating equipment.
	air conditioner	Also referred to as "AC".  A device that changes temperature and humidity levels and the quality of air.
	air flow volume	Measured in cubic feet per minute (cfm), this is the amount of air circulated in a space, or through a device.
	air handler	Parts of a system which push the air, including the blower fan, blower motor, filter system, and housing. The air handling components are a part of every forced-air furnace. There are also devices which move the air without heating it, and these are also referred to as air handlers.
	ARI	Air Conditioning and Refrigeration Institute, an independent testing organization for air conditioning appliances and equipment. Provide independent listings by manufacturer and model number of air conditioning ratings and efficiency.
	ASHRAE	American Society of Heating, Refrigeration and Air Conditioning Engineers. An independent consultation group.  Develop standards for the HVAC industry.
	BTU	British Thermal Unit. A unit of heat measurement.  One BTU is the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit.
	BTUh	British Thermal Units per hour. A measure of energy consumption. The measure of the amount of heat being transferred, created, or transformed.
	Burner	Component (usually in a furnace) that facilitates the combustion of the gas/air mixture for the purposes of converting the mixture to heat..
	Burner Orifice	The opening to the burner through which the gas or fuel passes prior to combustion. Functions much the same as a nozzle does on a garden hose. Orifices are precision-sized to deliver a pre-determined amount of fuel to the burner.
	Capacity	Heating capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.  Capacity will determine how much heat can be delivered to the house, building, or other conditioned space.
	Celsius	Also referred to as “Centigrade”, but Celsius is the scientist this standard was named after. A temperature scale that registers the freezing point of water as 0 degrees and the boiling point as 100 degrees under normal atmospheric pressure.
	Centigrade	see “Celsius”
	CFM	Cubic Feet per Minute – a measurement of air flow volume. Used to refer to the amount of air passing through a furnace to heat, cool, or ventilate.  Typical CFM requirement for an average home is between 1000 and 2000 CFM.
	charging a system	Adding coolant, or refrigerant, to an air conditioning system. More is NOT better.  A system uses a precise amount of refrigerant, based upon its capacity, and the characteristics of the compressor design.
	compressor	A pump that increases the pressure of gas. The driving heart of the air conditioner’s sealed refrigerant system, the compressor increases the pressure of the refrigerant it is processing, to the point where a vapor becomes a liquid.
	condensate	Vapor that is turned into a liquid as its temperature is lowered. An example of condensate: the droplets of water on the outside of a cool glass of iced tea, which come from the air, and not from inside the glass.
	condensate pump	Essentially, a shoe-box that fills with water, then empties itself into a drain when the box is full.  A condensate pump is used to remove condensed lwater from an air conditioner or the excess water from a humidifier.  A condensate pump is required in instances where the drain is higher than the water being produced.  When the normal down-hill tendency of water will not lead the water to a drain, the water is gathered in the tank of a condensate pump, and sucked out by a mechanical pump to a laundry sink, or some other suitable water receptacle.
	condensor	Also referred to as the “outdoor coil”. A device that removes heat from the refrigerant, allowing the refrigerant to be converted from vapor to liquid. When a condensor coil is operating it feels warm. This is the heat from your home that has been carried out to the condensor coil by the refrigerant, moved by the compressor.
	CSA	Canadian Standards Association. Self-described: “The Canadian Standards Association is a not-for-profit membership-based association serving business, industry, government and consumers in Canada and the global marketplace.”
	direct current (DC)	A type of electrical current that only flows in one direction, with constant polarity.  Typical source of DC is a flashlight battery.
	damper	Found at the exit points of ductwork, where the air enters the living space, the damper is a door or group of baffles that can be opened or closed to control the flow of air out of a register.
	degree-day	Calculated by subtracting the average outdoor temperature for an area from 65 degrees Fahrenheit. This measurement is used to estimate the amount of heating or cooling a home or building will need, based on the outside temperature. If the average outdoor temperature is below 65, it is referred to as a measure of “heating degree days” (HDD) and if the outdoor temperature is above 65 degrees, the difference is referred to as “cooling degree days” (CDD).
	dehumidifier	A device that removes humidity, or moisture from the air. A dehumidifier does not provide cooling to the space in which it is used, since cooling created in the dehumidification process is returned to the room as heat.
	downflow furnace	A furnace with an intake on the top and an air discharge at the bottom. Downflow furnaces are commonly used in one-story dwellings without basements, where the heat is delivered under the floor and up through wall or floor registers.
	drain pan	Also referred to as a “condensate pan”, “evaporator pan”, “a-coil pan” The water collected on the air conditioning coil surface drips down into a rain-gutter pan under your evaporator coil (still in the metal cabinet ABOVE your furnace). This pan is equipped with a drain fitting, which feeds out the side of the furnace, travels through a drain hose, and exits down your floor drain. (if the floor drain is not used, the furnace is equipped with a condensate pump.
	dry bulb temperature	The temperature as measured without the consideration of humidity. Dry-bulb temperature is the temperature you observe when you read a wall thermometer.
	ductwork	A network of metal, fiberboard (fiberboard is not our installation!) or flexible material conduits which delivers air from a heating or air conditioning unit to the respective living and work spaces of a building.
	EPA	Environmental Protection Agency – Government regulatory agency for land, water and air concerns.
	expansion valve	A valve that meters the levels of refrigerant, governed by a temperature or pressure control.
	evaporator coil	Also referred to as “indoor coil”, “a-coil”, etc. A device that is designed to absorb heat in the house air.  It is a radiator-like device inside the metal enclosure at the top of a furnace. The air conditioner supplies the evaporator coil with liquid refrigerant. As the house air heats the refrigerant, it vaporizes, and is transported, with the absorbed house heat, to the outdoor condensor unit, where the accumulated heat is extracted by the compressor.
	Fahrenheit	A temperature scale which references the freezing point of water at 32 degrees, and the boiling temperature of water at 212 degrees at normal atmospheric pressure.
	fan	In a furnace or air-handler it is  referred to as a “blower”. A mechanical device which creates air flow. Typical furnace blower assembly is a motor driving a squirrel-cage type fan in a metal housing.
	filter	As it applies to home heating and cooling equipment: a medium that acts like a strainer to remove dirt and unwanted particles from the air which passes through it.
	flue	The vent which removes byproducts of combustion from a furnace. Generally refers to high-temperature exhaust (above the boiling point of water).
	furnace	The major component for heating a home. A device that facilitates the safe combustion of fuel to create heat, and the transfer of that heat to the living space.  See also Heat Exchanger.
	fuse	A delicate metal strip connecting two parts of an electrical circuit. In the event of excessive current flow, precisely determined by the construction and consistency of the metal strip.  When the strip melts, this breaks the electrical circuit. Fuses are designed to stop the flow of electricity before it reaches a level which will damage other components in the circuit.
	GAMA	Gas Appliance Manufacturers’ Association. An independent non-government testing organization for home heating products.
	Heat Exchanger	A device through which heat is transferred to a cold area or surface. Essentially, it’s a metal box with a fire burning inside it. The fire heats the box, and things on the outside of the box get warm, but the fire itself vents outside through the chimney or exhaust vent, sealed safely away from the area it heats.
	Heat Loss	The amount of heat that leaves the living space, as through walls, ceiling, air leakage around windows, etc. This is the amount of heat that a furnace has to replace in order to maintain a constant temperature in the living space.
	Heat Pump	A device used for either the heating or cooling of a space by transferring heat between two areas. In the case of a home unit, the heat is transferred outside for air conditioning, and for heating the heat is extracted from the outside and delivered into the home.
	heat transfer	Moving heat from one location to another.
	humidifier	a device which adds humidity, or moisture, to the air. Humidifiers typically operate by passing the house air through an evaporative surface that is constantly replenished by a water source.
	humidistat	A device which turns a switch on and off based on the humidity of the room. The switch controls a humidifier unit, which supplies needed humidity to the air, and then switches off when the humidistat senses that there is enough humidity in the room.
	humidity	The moisture content of air. Moisture can be removed from the air by dehumidifiers and air conditioning. Moisture can be added to the air by a humidifier. Next to temperature, humidity is the most important ingredient to personal home comfort
	HVAC	Heating, Ventilating and Air Conditioning. An industry shortcut term, does not refer to any particular brand of equipment, or organization.
	Ignition	Starting a combustion reaction. For example, lighting a gas flame. The gas must come in contact with a high enough temperature that it “catches fire”. This is done in furnaces by a standing pilot (a small fire which burns all the time), or a spark ignition, or a glowing red-hot heating element.
	kilowatt	a measure of electrical energy. A kilowatt equals 1000 watts, and a watt is 1 amp delivering at 1 volt. While kilowatts measure how strong the energy usage is, to measure how much electricity has been used, as the power company measures, the kilowatt load is multiplied by the number of hours the power is utilized. The unit of measure for electricity usage is the kilowatt-hour. For example, a 100-watt light bulb burning for 10 hours uses 100 x 10 = 1000 watt-hours, or one kilowatt hour.
	Latent Heat	The heat that is stored in the objects and fixtures (for example walls, carpets, furniture, draperies) of a living space. To reduce the temperature of the room, the latent heat of the objects must be taken into account when calculating the cooling requirement of the space.
	Media	The air-permeable fine material of a filter that traps dirt, dust, mildew or bacteria. Alternatively, the air-permeable mesh material of a humidifier pad which transfers moisture to the air passing through it.
	NEC	National Energy Council / National Electric Code
	NEMA	National Electrical Manufacturing Association – An independent organization which maintains uniform standards for electrical fittings and equipment.
	orifice	An opening of a precise diameter which limits the flow through the opening. Examples: gas orifice regulates the amount of gas which can pass from a gas valve to a burner. Water orifice in a humidifier regulates how much water can flow through the humidifier.
	plenum	the metal ductwork which connects the furnace or air handler to the house air system.  Typically, a plenum is air-tight, and connects to the furnace, and to the distribution network of air conduits to the individual rooms of the home.  If the home has central air conditioning, the plenum is also the place at which the transfer of cooling to the house air takes place.
	PSI	Pounds per Square Inch – a measure of air or water pressure.
	PVC	Poly-Vinyl Chloride – a type of plastic. In heating, PVC is used for the intake and exhaust (white) pipes of a high-efficiency furnace.
	Reciprocating Compressor	A type of compressor used in cooling systems to compress refrigerant by using a piston action.
	Refrigerant	A chemical that condenses from a vapor to liquid in a practical temperature range for home heating and cooling. In the process of evaporating, the refrigerant absorbs heat, and when it turns to liquid, it releases heat.
	Refrigerant Charge	The total amount of refrigerant in a system. Measured by weight, usually in pounds.
	SEER	Seasonal Energy Efficiency Ratio. A rating system developed by the U.S. Government to indicate the efficiency level of cooling equipment.
	sensor	a general term for a device that reacts to a change in conditions. For home heating and cooling applilcations, sensors react to temperature, humidity, air pressure, vacuum, etc.
	split system	two pieces of equipment, one indoor and one outdoor working together in an HVAC system, for example, an air conditioning system..
	Thermostat	A temperature sensor which monitors the output of a heating or air conditioning system, switching the system on and off as needed to maintain the temperature at which the thermostat has been set.
	Thermostatic Expansion Valve (TXV)	A device that creates a constant evaporator temperature by regulating the supply of refrigerant entering the evaporator.
	Ton	A measure of heat capacity. One ton is 12,000 BTUs per hour.
	upflow furnace	A furnace that pulls in air from the bottom and releases it through the top. Most basement furnace installations use upflow units.  The cold air return connects to a sheet-metal duct which leads house air to the bottom of the furnace where it is heated and returned to the home through the plenum of the furnace
	vacuum	A space where the pressure is significantly below that of standard atmospheric pressure.
	volt	Unit of measurement for electromotive force. Voltage is how strongly the electricity will push if the circuit is allowed to complete.
	watt	unit of measurement for power, equal to the flow of one amp at a voltage of one volt. A 100-watt light bulb at 110 volt service will draw approximately 1.1 amp. Consumption is measured at watt usage over time (watt-hour).
	wet-bulb thermometer	a thermometer that measures the relative humidity in the air, based on the heat extracted by evaporation of water on a cloth thermometer bulb.
	zoning	as it applies to home climate control, a home or office is divided into different regions, called zones. Each region has its own temperature control. This zone system gives a larger area more even temperature control, or can supply special temperature settings for areas with special temperature needs.

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