GLOSSARY TERMS Air Conditioning, Heating, and Refrigeration Institute
Carbon Monoxide A colorless, odorless but poisonous combustible gas produced by incomplete combustion of fuels such as natural gas, L.P., coal, and gasoline. Chiller (Air-Cooled) A device that removes heat from a liquid such as water with compressors and refrigerant. Air cooled chillers are usually outside and consist of condenser coils cooled by fan driven air. Chiller (Water-Cooled) A device that removes heat from a liquid such as water with compressors and refrigerant. Water cooled chillers are usually inside a building, and heat from these chillers is carried by recirculating water to a heat sink such as an outdoor cooling tower. Coefficient of Performance Ratio of tons of refrigeration produced to energy required to operate equipment. Combustion Efficiency A measure of how effectively the heat content of a fuel is transferred into usable heat. Computer Room Air Conditioner A packaged direct expansion air conditioning unit designed specifically for computer room, data center, and heat intensive spaces. Cubic Feet Per Minute This measurement indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air that is being forced through the ductwork by the system. Demand Controlled Ventilation A control and sensor system that allows the HVAC system to determine the proper level of ventilation air required based on actual building occupancy. This reduces unnecessary heating and cooling loads and saves energy. Direct Current A type of electricity transmission and distribution by which electricity flows in one direction through the conductor: usually relatively low voltage and high current. Direct Expansion Air conditioning and refrigeration systems in which the cooling is obtained directly from the expansion of the liquid refrigerant into a vapor. System components include coils, compressors, evaporators, and expansion valves.
Domestic Hot Water Water heated for domestic or commercial purposes other than space heating and process requirements. Common uses include washing, bathing, and cooking. Dry Bulb The sensible temperature of the air as measured by a standard thermometer. Drycooler A drycooler is similar to an air-cooled condensing unit, but utilizes a liquid solution, such as water, ethylene glycol/ water, or propylene glycol/water, to transfer heat in lieu of refrigerant and compressors. Economizer A method of operating a ventilation system to reduce refrigeration load. Whenever the outside air conditions are more favorable (lower heat content) than return air conditions, outdoor air quantity is increased. Efficiency or Effectiveness Typically used in reference to ERV systems. It is the ratio of energy transferred between the two air streams compared with the total energy transported through the heat exchanger. Electronically Commutated Motor A motor that uses a permanent magnet design to generate a rotating magnetic field. The rotating magnetic field causes the axle to rotate, spinning the fan. These motors are also referred to as brushless DC motors or Solid State Commutator (SSC) motors. Energy Efficiency Ratio The measure of the instantaneous energy efficiency of air conditioners; the cooling capacity in BTU/hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit). Energy Management System A microprocessor-based system for controlling equipment and monitoring energy and other operating parameters in a building. Energy Recovery Ventilator A device that captures the sensible and latent heat from the exhaust air from a building and transfers it to the supply/fresh air entering the building to preheat the air and increase overall heating efficiency. Enthalpy The total heat content of air expressed in units of BTU/pound. It is the sum of the sensible and latent heat.
(AHRI) is the trade association representing manufacturers of HVACR and water heating equipment within the global industry. It includes a certification program that provides accurate and unbiased evaluation of heating, water heating, ventilation, air conditioning, and commercial refrigeration equipment. AHRI develops industry- recognized performance standards for equipment. Air Handling Unit The part of the central air conditioning or heat system that circulates heated or cooled air through building ductwork. Boiler (Condensing) Condensing boilers heat water at higher efficiencies (greater than 90%) by using the waste heat in the flue gases to preheat the cooler water entering the boiler. The term "condensing" refers to the water vapor that collects in the boiler flue from the reduced exhaust temperatures. Boiler (Near Condensing) Near condensing boilers heat water at efficiencies between 85% and 89% by using the waste heat in the flue gases to preheat the cooler water entering the boiler. These boilers typically do not cool the flue exhaust enough to cause "condensing" of the water vapor in the boiler flue. Boiler Horsepower A measure of a boiler's capacity to produce steam. The amount of energy needed to produce 34.5 pounds of steam per hour at a temperature of 212 degrees Fahrenheit into steam at 212 degrees Fahrenheit. Brake Horsepower The brake horsepower is the amount of actual horsepower going to the pump or fan, not the horsepower used by the motor. The actual power delivered by a motor is measured by the use of a brake. British Thermal Units A measurement of energy. The amount of heat required to raise the temperature of one pound of water 1 degree Fahrenheit at or near 39.2 degrees Fahrenheit. British Thermal Units Per Hour The number of BTUs consumed or generated in a one-hour period. Carbon Dioxide A colorless, odorless noncombustible gas with the formula CO 2 that is present in the atmosphere. CO 2 is a natural by-product of respiration.
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