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NORA Oilheat Technicians Manual

Oilheat Technicians Manual Carbon Monoxide (CO): A gas which, in heating practice, indicates incomplete combustion of the carbon in the fuel and is found through analysis of the flue gas. Centigrade: See “Celsius.” Celsius: A thermometer scale at which the freezing point of water is 0° and its boiling point is 100°. In the United States it is only used in scientific and laboratory work. Chimney Effect: The tendency of heated air or gas in a vertical passage to rise due to lower density compared to that of the surrounding air or gas. In buildings, the tendency of the cold, denser outside air to replace the heated air results in the “chimney effect.” Circuit (Electrical): The complete path of an electric current from the source through a switch to a load and back to the source. Circuit Breaker: A thermal device which opens a circuit when the current in the circuit exceeds a predetermined amount. Cloud Point: The temperature at which wax crystals begin to form in fuel, typically 10 to 20 degrees above pour point. Combustion: Defined as the rapid reaction of combustible material with oxygen, with the resultant generation of heat. For combustion to take place, the fuel must be heated to its ignition temperature and brought into contact with oxygen. Combustion Chamber: The refractory or metal lined area within a boiler or furnace in which the combustion of fuel takes place. When no chamber is present (as in wet base boilers) the area is often referred to as “combustion space.” Comfort Zone (Average): The range of effective temperatures over which the majority of adults feel comfortable. Condensate: Liquid formed by the condensation of a vapor,;in steam heating, water condensed from steam. Conduction: The process of diffusion or flow of heat energy through a mass, or body of matter, by particle of molecular contact from the warmer to the colder parts. Conductor (Thermal): A material capable of readily transmitting heat by means of conduction. Conductor (Electrical): Any material suitable for carrying electric current. Convector: A concealed radiator. An enclosed heating unit located (with enclosure) either within, adjacent to, or exterior to, the room or space to be heated, but transferring heat to the room or space mainly by the process of convection. Converter: A piece of equipment for heating water with steam without mixing the two. It may be used for supplying hot water for domestic purposes or for a hot water heating system. Cycle (Electrical): One complete positive and one complete negative alternation of a current or voltage. Degree-Day (Standard): A unit which is the difference between 65°F and the daily average temperature, when the latter is below 65°F. The degree days in any one day is equal to the number of degrees F that the average temperature for that day is below 65°F. Dew Point: The temperature below which water vapor contained in flue gases turns to a liquid. This change is referred to as condensation. To prevent condensation, stack temperature should range from 270°F to 370°F above ambient air temperature. Dielectric: An insulator. The insulating material between the plates of a capacitor. The insulating porcelain of an ignition electrode. Direct Current: An electric current that flows in one direction only. Direct Return System (Hot water): A two-pipe hot water system in which the water, after it has passed through a heating unit, is returned to the boiler along a direct path, so that the total distance traveled by the water, from each radiator, is the shortest feasible. Direct Venting: The mechanical exhausting of the flue gases of a heating unit in a structure that does not have a suitable chimney. Down Feed System: A heating system in which the supply mains are above the level of the heating units which they serve. Draft: In heating systems, draft refers to the pressure difference which causes a current of air or gases to flow through a combustion chamber, flue, chimney or space. Efficiency: In a heating unit, it is that percentage of the heat energy input which is useful energy output. The ratio of output power to input power is generally expressed as a percentage. Electromagnet: A magnet made by passing an electrical current through a wire wound on a soft iron core. Electromotive Force (emf): The force that produces an electric current in an electric circuit. Oilheat Technicians Manual—IX


NORA Oilheat Technicians Manual
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