HVAC TERMINOLOGY.Pdf

HVAC TERMINOLOGY Abatement Reduction or removal of a contaminant. Absolute Humidity It is the ratio of the mass of water vaporto the unit volume of moist air represented in grams per cubic foot (g/ft3). Absolute Zero Temperature at which all molecular motion ceases (-460 F. and -273 C.). Absorption Refrigerator Refrigerator which creates low temperature by using the cooling effect formed when a refrigerant is absorbed by chemical substance. ACCA Air Conditioning Contractors of America - a leading HVAC/R Association. Acceptable indoor air quality Indoor air that does not contain harmful concentrations of contaminants; air with which at least 80% of building occupants do not express dissatisfaction. Accumulator Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing. Tank on the suction side of a system that holds excess refrigerant to prevent slugging the compressor with liquid. ACH Air Changes Per Hour. The number of times that air in a house is completely replaced with outdoor air in one hour. Acid Condition In System Condition in which refrigerant or oil in system is mixed with fluids that are acid in nature. ACR Tubing Tubing used in air conditioning and refrigeration. Ends are sealed to keep tubing clean and dry. Activated Carbon Specially processed carbon used as a filter drier ; commonly used to clean air. Actuator That portion of a regulating valve which converts mechanical fluid, thermal energy or insulation energy into mechanical motion to open or close the valve seats. Adiabatic Compression Compressing refrigerant gas without removing or adding heat. Adjustable Grille A grille with linear blades which can be adjusted to vary the direction of the discharged air. The linear blades are normally either vertical or horizontal, or both horizontal and vertical. Adsorbent Substance with the property to hold molecules of fluids without causing a chemical or physical damage. Aeration Act of combining substance with air. AFLU (Annual Fuel Utilization Efficiency) A rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust. AFUE (Annual Fuel Utilization Efficiency) This number represents how efficiently a furnace converts fuel to energy. The ratio of annual output of useful energy or heatto the annual energy inputto the furnace. The higher the AFUE, the more efficient the furnace -- higher efficiency translates to more savings on fuel bills. This will range from 80% to 95%. Percentage of fuel used for heating. A measure of heating efficiency, in consistent units, determined by applying the federal test method for furnaces. This value is intended to represent the ratio of heat transferredto the conditioned space by the fuel energy supplied over one year. Air Conditioner Device used to control temperature, humidity, cleanliness and movement of air in a confined space. Air Conditioning Control of the temperature, humidity, air movement and cleaning of air in a confined space. Air Diffuser Air distribution outlet or grille designed to direct airflow into desired patterns. Air Exchange Rate The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time in air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time - cubic feet per minute (cfm). Air Handler The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. In some systems a furnace handles this function. Allergens and Pathogens Biological material, including bacteria, viruses, fungi, mold spores, pollens, skin flakes and insect parts are ubiquitous in indoor environments. These particulates range from less than one to several microns in size. When airborne, they are usually attached to dust particulates of various sizes so that all sizes of airborne particulates may include them. Ambient The surrounding atmosphere; encompassing on all sides; the environment surrounding a body but undisturbed or unaffected by it. Ambient Air The air surrounding a building; outside air. Ambient Air Temperature Surrounding temperature, such as the outdoor air temperature around a building. Ampere (A or Amp) The primary unit of measurement of insulation current. Amps multiplied by Volts determines Watts. Electricity bills are based on watts or kilowatts (a thousand watts) per hour. ARI Air-Conditioning and Refrigeration Institute is a nonprofit, voluntary organization comprised of heating,air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners to provide you with a standardized measure of comparison. So, ARI ensures a level of performance within the industry. ASHRAE A leading HVAC/R Association - American Society of Heating, Refrigerating and Air Conditioning Engineers - http://www.ashrae.org/ The trade association that provides information and sets standards for the industry. ASTM American Society for Testing and Materials. top [ B ] Balance Point An outdoor temperature, usually between 30° F and 45° F, at which a heat pump's output exactly equals the heating needs of the home. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort. Blower An air handling device for moving air in a distribution system. Boiling Point The temperature at which the addition of any heat will begin a change of state from a liquid to a vapor. BTU (British Thermal Unit) The standard of measurement used for measuring the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit). BTUH - The number of BTUs in an hour. BTU/hr The abbreviation for British thermal units per hour. The amount of heat required to raise one pound of water one degree fahrenheit per hour, a common measure of heat transfer rate. Building Envelope Elements of the building, including all external building materials, windows, and walls, that enclose the internal space. top [ C ] Capacity The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTU's. For cooling, it is usually given in tons. Central Air Conditioner System System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts. Centrifugal Compressor A type of compressor used in vapor compression refrigeration cycles where a rotating impeller is the device which compresses the refrigerant vapor. The vapor is drawn into the impeller axially, and is discharged radially after energy is addedto the vapor within the impeller. CFM (Cubic Feet per Minute) The abbreviation for cubic feet per minute, commonly used to measure the rate of air flow in an air conditioning system. Charge Amount of refrigerant in a system. Comfort Air Conditioning Comfort air conditioning systems are designed for the comfort of people, not the protection of computer-based insulation systems. Unlike people, computers generate dry (sensible) heat, but not humidity. Only about 60-70% of a comfort system's total capacity is dedicatedto the removal of sensible heat, while 30-40% is for dehumidification. With a large percentage of their total capacity devotedto the removal of moisture, comfort systems can lower room humidity far below acceptable standards. A larger comfort system is required to obtain the same sensible capacity as a precision cooling system. Compressor The pump that moves the refrigerant from the indoor evaporatorto the outdoor condenser and backto the evaporator again. The compressor is often called "the heart of the system" because it circulates the refrigerant through the loop. Condensation The process by which a gas is changed into a liquid at constant temperature by heat removal. Condenser A device that transfers unwanted heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) that absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled condensers, water- cooled condensers, and evaporative condensers. The evaporative condenser uses a combination of air and water as its condensing medium. Most residential systems have an air-cooled condenser. Condenser Coil A series or network of tubes filled with refrigerant, normally located outside the home, that removes heat from the hot, gaseous refrigerant so that the refrigerant becomes liquid again. Condensing Unit Part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns itto the refrigerant control. The outdoor portion of a split system air conditioner contains the compressor and outdoor coil ignoring the reverse cycle operation, also the outdoor in a heat pump system. Cooling Capacity A measure of the ability of a unit to remove heat from an enclosed space. COP - Coefficient of Performance of a heat pump means the ratio of the rate of useful heat output delivered by the complete heat pump unit (exclusive of supplementary heating)to the corresponding rate of energy input, in consistent units and under operating conditions. Cooling Load Heat which flows into a space from outdoors and/or indoors. top [ D ] Damper Found in ductwork, this movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms. Dehumidification The reduction of water vapor in air by cooling the air below the dew point; removal of water vapor from air by chemical means, refrigeration, etc. Department of Energy (DOE) A federal agency that sets industry efficiency standards and monitors the use of various energy sources. Direct Vent Pulls outside air for combustion and vents combustion gases directly outside.

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