Document KROZnbNjdqpgG1Z5Jqj1VKnrX

American Society of Heating and Ventilating Engineers Guide, 1929 Factory work permits greater friction allowance for the heaters where duct runs are comparatively short and the resistance of the heater is a large part of the entire pressure loss in the system. The fan can be selected when the following facts are knowh: 1. Quantity of air required in cubic feet per minute. 2. Static pressure of system (ducts, heaters, air washers, filters, entrance connections, etc.). For data on selection of fans, see Chapter XXVI. The quantity, velocity and pressure of air delivered by the fan should be determined by the A. S. H. & V. E. Standard Code for Testing Cen. trifugal and Disc Fans (See Transactions, 1923, Vol. 29, p. 407). . .A fan installation rightly designed and operated will be quiet and efficient, but every precaution should be taken to prevent vibration or sound transmission to the rooms. It is usually more effective to float the entire mechanical apparatus on cork, including its foundations, than to attempt to isolate each separate apparatus. There are several systems for the sound-proofing of machinery available, and contracts may be made covering guaranteed and assured results. For data on ventilation requirements for different kinds of buildings and for the effects.of ventilation see Chapter XXIII, Modern Standards of Ventilation and Measurement of Air Quality and Quantity. For data on Air Conditioning and Cooling, see Chapter XXV. For data on the Use of Ozone in Ventilation, see Chapter XXX. For further guidance in determining the quality of ventilation usually desirable for different kinds of buildings and in the selection of the class pf ventilating apparatus which may be used for meeting these respective requirements the following data is given. : TYPES OF EQUIPMENT SUGGESTED FOR ATTAINING SPECIFIED SYNTHETIC AIR CHART PERCENTAGES ' The following classification is given to assist in selecting the type of equipment necessary to attain certain percentages on the Synthetic Air Chart. It will be understood that considerable variation may be found in certain classes of equipment due to, the individual ideas on the part of the designer; the character of the installation work, the location of the building in which the equipment is installed, etc.; nevertheless, if the equipment ,is; properly designed, installed and. operated, it will give at least .the, percentage-listed -under any particular classification. To'design an.installation approaching. 100 per cent, it is necessary .to provide ap? paratus lor, heating and humidifying the air, for thoroughly cleaning it and properly, distributing it with controlling devices that will maintain the temperature and humidity; in conformity with the comfort lines as given by the Research Laboratory of the American Society of Heating and Ventilating .Engineers'. .Any equipment omitted or any part .that is ineffective will, reduce: the .final percentage attained. Class "A" equipment capable of attaining over 95.per cent.on the 386 Chapter XXIV--Systems of Ventilation Synthetic Air Chart, consisting of a mechanical system including the following apparatus: 1. oMceccuhpaannitc. al air supply having a maximum capacity of 30 cu. ft. per minute per 2. Mechanical exhaust equipment. , 3. Excellent air distribution. 4. Accurate automatic temperature control. 5. Efficient humidifying apparatus. 6. Accurate automatic humidity control devices. 7. Efficient air cleaning apparatus. Note.--It is understood that 100 per cent efficiency is a physical impossibility since this would mean 100 per cent efficiency in the air cleaning device, in air distribution, in temperature control, etc. Perfect results of this kind have not yet been obtained in practice, although it is possible to obtain approximately s9k9ilplfeurllcyeonpt eorfattheed.Synthetic Air Chart with an apparatus of this kind carefully designed and installed and Class "B" equipment capable of attaining from 90 to 95 per cent on the Synthetic Air Chart, consisting of a mechanical system including the. following apparatus: 1. oMceccuhpaannitc.al air supply having a maximum capacity of 30 cu. ft. per minute per 2. A well designed gravity exhaust system. .... 3. Efficient air distribution by properly located supply and exhaust registers. 4. Automatic temperature control. 5. Adequate humidifying apparatus. '. 6. Automatic humidity control. .. ; , Note.--All.cleaning devices have been omitted from Class "B" as 95 per cent can be obtained under ordinary conditions-without air cleaning. In exceptionally clean localities higher percentages will result. Where the air contains considerably more than the average amount of dust slightly lower percentages may result. Air cleaning apparatus may be substituted in Class " B" for automatic humidity control without' materially affecting the final percentage. ' Class " C" equipment capable of attaining from 85 to 90 per cent, on the Synthetic Air Chart, consisting of a mechanical system including the following apparatus: 1. Mechanical air supply having a maximum capacity of 30 cu. ft. per minute per- occupant.'" ~; 2. Gravity exhaust. 3. Efficient air distribution by properly located supply and exhaust registers. 4. Automatic temperature control. . , 5. Adequate humidifying apparatus. ,6. Humidity control from one or more selected points or manual control. Class "D" equipment capable of attaining 80 to 85 per cent ion the: Synthetic Air Chart, consisting of a mechanical system including the following apparatus: 1. Mechanical supply having a maximum capacity of 30 cu. ft. per minute' per ' ' Occupant. ' /' . . 2. Gravity exhaust. 3. Good air distribution. .- 4. Automatic temperature control from one or more selected points or manual control. 387;