Document N2dQyzR8Xrq3EjXBpKpnDXBdE

442 CHAPTER 21 ; 1949 Guide ' "' : -." ' REFERENCES ';; '< < The engineering data were.obtained from University of Illinois' Engineering Experiment Station Bulletins Nos. 141^ 188,189 and 246; Warm Air Furnaces and Heat ing Systems, by^A. ;C. Willard, A. P. Kratz,V. S. Day, and S.Konzo. See also de and Manual for Gravity Warm. Air Heating.Systems, published by the National Warm Air Heating and Air Conditioning Association. ' . * Simplified Procedure for Selecting Capacities of Duct Systems fo* Gravity Warm- Air Heating Plants, by A. P. Kratz and S. Konzo (Universityof Illinois Engineering Experiment Elation Circular 45,-Dec., 1942).;- : . Gravity Code and Manual for Gravity Warm Air Heating Systems, Second Edi.tin, 1945, National Worn Air Heating and. Air Conditioning Association. :,-fi ;f U . -i' - . ; .'I ^ L'-:; -< . >.. ;;t? . ' - 1 . >;\ . t:sH: -I S.4 l-f l-.' \ ,V\ '< a ' : . ' 'ff i. ' i- -v;.' t.'-.-y/ : .. I y.-: : . *, ; ; 'J'. 1 . - . `y` ; . ; M _.v / , 7i . CHAPTER 22 MECHANICAL WARM AIR SYSTEMS Air Distribution, Standard Combinations of Parts, Simplified Design of Heating \ System, Automatic Controls, Design Procedure for Larger Systems, Adjustment of System for Continuous Air Circulation, Cooling Methods IN mechanical warm air.or fan furnace heating systems', the air circula-. tion is effected by motor-driven centrifugal fans, commonly referred toas blowers, instead of by the difference in weight between the heated air leaving the top of the casing and the cooled air entering the bottom, as in gravity systems described in Chapter 21. . The advantages of mechanical systems, as compared with gravity systems, are: 1. The furnace need not be centrally located but may be placed in any part of. the basement. , 2. Basement distribution piping can be made smaller and can be so, installed as to ; < give full head room in all parts of the average basement, or'be completely-concealed from view where desired. : ' 3. Circulation of air is positive, and in a properly designed system can be:balanced -li in such a way as to give a greater uniformity .of temperature distribution. ... 4. Humidity control is more readily attained. i'1 5. The air may be cleaned by sprays or filters, or both. 6. The fan and duct equipment may be utilized for a complete cooling and dehumidifying system for summer, using either ice, mechanical refrigeration, or low temperature water for cooling and dehumidifying,"or adsorbers for dehumidifying. - 7. The use of the fan increases the'volume of air which can be handled, thereby increasing the rate of heat extraction from a given amount'of heating surface and insuring sufficient air volume, to obtain proper distribution in a.large room. 8. Ventilation air may be positively introduced and heated. * The construction features of mechanical warm air furnace units and dis cussions' of th& function and selection of the various parts, such as the furnace, casings, motors, filters and controls are included, in Chapter 18. AIR DISTRIBUTION The conditions of comfort obtained in a room are influenced greatly by ' the type of register used and the locations of the supply registers and.retum grilles. In general it has been found that changes in the type, air. velocity, and location of the supply register affect the room conditions much more' than the changes in the location of the return grilles. . One method is to locate the supply register near the floor, or high in the side wall, so that the warm air from the register blankets a cold wall, and mixes with the cold air' descending from the exposed walls and glass. Another method is. to locate the supply openings near the floor, or high in the side wall, on the inside wall and the return openings near the greatest outside exposure. In any case the warm air registers should be located so that the air stream never discharges directly into space that will normally be'occupied by-people at. rest. iTests in the Warm Air Research Residence1 have indicated'that OOUt tinuous blower operation gave better results than intermittent operation, 443