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American Society of Heating and Ventilating Engineers Guide~193j are desirable to provide a factor of safety and to allow for- more circulation for summer cooling; raP*d For additional information on fans and motors, see Chapter 17 NOISE ELIMINATION Special attention must be given to the problem of noise elimination The fan housing must not be directly connected with metal, either to the furnace casing dr to the return air piping. It is common practice to use canvas strips in making these connections. Motors and their mountings must be carefully chosen for quiet operation. Electrical conduit and water piping must not be fastened to, nor make contact with, fan housing. The installation of a fan directly under a cold air grille is not recommended on account of the noise objection. See also Chapter 18. AIR WASHERS AND FILTERS Washers for residence systems may be provided in separate housings to be installed on the inlet or outlet side of the fan, or they may be integral with the fan construction. They operate at water pressures of from 10 to 30 lb and use two or more spray nozzles for washing and humidification. The sprays should be adjusted to completely cover the air passages. Washers are usually controlled by solenoid valves wired in parallel with 378 -Mechanical Warm Air Furnace Systems w . -iji- motor. The water supply may, in turn, be controlled by a .controlling device located in one of the living rooms,, so that the will operate at all times when the fan is in operation, unless the v otive humidity should rise beyond a desirable percentage. Washers 'in' connection with commercial qr heavy duty plants should be a ?iSulation type of commercial washer. ^hete are may satisfactory types of filters on the market. These ,u(jg dfy filters, viscous filters, oil filters and other.types, some of which - ? st fig cleaned, some of which must be cleaned and recharged with oil, some of which are inexpensive and may be discarded when they kcome dirty, and replaced with new ones. The resistance of a filter must be considered in the design of the system since'the resistance rises rapidly as the filter becomes dirty, thus imnairiug the heating efficiency of the furnace, in fact, endangering the life if the furnace itself. Manufacturers' ratings of filters must be carefully regarded, and ample filter area must be provided. Filters must be Solaced or cleaned when dirty. See also Chapter 16. COOLING METHODS . i_' '.i'*' j. .*' Some cooling may be obtained under certain conditions by the use of basement air. A more positive cooling effect may be obtained through air washers where the temperature of the water is sufficiently low (55 F or .lower), and where a sufficient volume of water can be provided. Unless (the water is below the dew point temperature of the indoor air at the time . the washer is started, both the relative and absolute humidities will be somewhat increased. . Coils of copper finned tubing through which cold water is pumped are -available for cooling. They require less space than air washers and have the advantage that no moisture is added to the air when the temperature of the water rises above the dew point. Ample coil surface is necessary -with this type of cooling. It is thoroughly feasible to use ice or mechanical refrigeration in con nection with the fan and duct system for the heating installation, and to '.' cool the building by this method,, provided the building is reasonably well constructed and insulated. Windows and doors should be tight, and awnings should be supplied on the sunny side of the building. See also Chapters 9 and 10. - Study of these problems sponsored by the American Society of Heating and Ventilating Engineers in cooperation with the National Warm Air Heating Association is in progress at the University of Illinois. The following conclusions may be drawn from the studies thus far com pleted, subject to the limitations of the conditions under which the tests were run1: 1. An uninsulated building of ordinary residential type may require the equivalent of three tons of ice in 24 hours on days when the maximum outdoor temperature reaches 100 F if an effective temperature of approximately 72 deg. is maintained indoors. "See A.S.H.V.E. research paper entitled Study of Summer Cooling in the.Research Residence at the - University of Illinois, by A. P. Kiatz and S. Konzo (A. S. H. V. E. Journal Section Heating, Ptptng and Atr Conditioning, February. 1933). 379