Document wDgYa4m1vjqrmgoXzxXr08z2Q

Heating Ventilating Air Conditioning Guide 1939 and thus provides a larger plenum chamber. Fig. 3 illustrates a complete residence fan furnace installation showing location of fan, furnace, filters plenum chamber and method of take-off of warm air pipe. ' FANS AND MOTORS Centrifugal type fans are most commonly used, and these may be equipped with either backward or forward curved blades. Motors may be mounted on the fan shaft or outside of the fan with belt connection. Multi-speed motors or pulleys are desirable to provide a factor of safety and to allow for increased air circulation. For additional information on fans and motors, see Chapters 27 and 38. SOUND CONTROL Special attention should be given to the problem of noise elimination. The fan housing should not be directly connected with metal, either to the furnace casing or to the return air piping. It is common practice to use canvas strips in making these connections. Motors and their mountings must be carefully selected 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 30). FILTERS There are many satisfactory types of filters on the market. These include dry filters, viscous filters, oil filters and other types, some of which must be cleaned, some of which must be cleaned and recharged with oil, and some of which are inexpensive and may be discarded when they become dirty, and replaced with new orifes. 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 im pairing the heating efficiency of the furnace, in fact, endangering the life of the furnace itself. Manufacturers' ratings of filters must be carefully regarded, and ample filter area must be provided. Filters must be replaced or cleaned when dirty. (See also Chapter 26). AIR DISTRIBUTION The conditions of comfort obtained in a room are greatly influenced by the type of register used and the locations of the supply registers and return 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. Due to the economic considerations involved, it is common practice to locate the supply openings on-the inside walls of a residence and the return openings nearest the greatest outside exposure.. Many designers prefer, however, to locate the supply registers so that the warm air from the registers blankets a cold wall, and mixes with the cold airdropping off from the exposed walls. This may be accomplished by the use of a supply register placed close to an outside wall in such-a position that the.warm air sweeps 402 Chapter 20. Mechanical Warm Air Furnace Systems the cold wall surface. The ducts leading to supply registers which are located on exposed walls should be adequately insulated to reduce the ins from the ducts. Register and Grille Openings Supply registers located in the floor are effective, but as they require frequent attention to keep them clean they should be avoided where another effective register location can be found. Tests conducted in the VVarm Air Research Residence* have indicated that excellent results are obtainable with the use of a deflecting-diffuser type of baseboard register which throws the air downward toward the floor and diffuses the air at the RETURN AIR DUCTS aCT SUPPLY DUCTS TO ROOMS RECIRCU_AT1NG dv^er FILTI CreCT EXF*NSCN COOLING CONDENSING WATER INLET. Fig. 3. REFRIGERATING MACHINE CONDENSING WATER OUTLET FOR SPRINKLING OR WASTE Complete Residence Fan Furnace Installation for Winter Heating and Summer. Cooling same time. Unless registers located in the baseboard are well proportioned and designed to harmonize with the trim, they may. be unsightly. Better air distribution for cooling is obtained when high side wall registers are used, and this same location is satisfactoiy for, heating when the openings are installed at least 7 ft above the floor'line, providing the air velocity through the registers is greater than. 600 fpm. Registers which; are located in side walls above the baseboard or in the ceiling should be bf.an effective air-diffusing type. . All registers should, be equipped with dmaamrgpienrss., and sho-u. ld: be sealed agains.t...l.e..a..k.age around the borde. rs...or., Velocities through registers may be reduced by the use of registers larger than the connecting-pipes. Some'suggestions for equalizing velocitaes over the face area of the. register by, means of diffusers, are illustrated' ln Fig. 4. Merely to use a larger register may not result.;in materially reduced velocities unless diffusers are used.