Document gaNK5g72RaJLqe5LbM8wG8LO3

Heating Ventilating Air Conditioning Guide 1939 . o S'3' **; 3 H s,a< aggg*0 <ogg o a, 5*Sj F ig . 8. H e a te r A rranged for Pa r t ia l Recirculation . A lso Show ing M ix in g D amper from .Warm A ir a n d T em pered A ir Ch am ber s, and Par tial E xhaust to A tmosphere F ig . 9. H eater A rranged (A) w ith H eated A ir to pering , Sh o w in g M ix in g T empered A ir and Chapter 20. Mechanical Warm Air Furnace Systems . . jatent heat of evaporation can be taken, such heat is supplied ..' whichth, e air. TThhperree iiss., therefore, a trend in present practice toward [l01"- the water in addition to heating the air. Equipm---e--n--t--f-o--r---d-o--i-n- ,,g , heauug ma^e use 0f sprays, or it may take the form of water circulating 'olaced within the combustion chamber and connected by pipes to i l .midifier pans where a constant water level is maintained by some karateW device. (See Chapter 25.) Sorays for residence systems may be provided in separate housings . v, jpStalled on the inlet or outlet side of the fan, or they may be 'teeral with the fan construction. They operate at water pressures of "1 m 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. Sprays are usually controlled by solenoid valves wired in parallel with the fan motor. The water supply may, in turn, be controlled by a humidity-controlling device located in one of the living rooms, so that the washer will operate at all times when the fan is in operation, unless the relative humidity should rise beyond a desirable percentage. Sprays used in connection with commercial'or heavy duty plants should be a regulation type of commercial spray. Residence Requirements The principles underlying humidity requirements and limitations for residences are summarized in University of Illinois Bulletin No. 2304, as follows: 1. Optimum comfort is the most tangible criterion for determining the air conditions within a residence. 2. An effective temperature of 65 deg6 represents the optimum comfort for the majority of people. Under the conditions in the average residence a dry-bulb tempera ture of 69.5 F with relative humidity of 40 per cent is the most practical for the attain ment of 65-deg effective temperature. 3. Evaporation requirements to maintain a relative humidity of 40 per cent in zero weather depend on the amount of air inleakage to the average residence, aiid vary from practically nothing to 24 gal of water per 24 hours. 4. Relative humidity of 40 per cent indoors cannot be maintained in rigorous climates without excessive condensation on the windows unless, tight-fitting storm sash or the equivalent is installed. 5. The problems of humidity requirements and limitations cannot be separated from considerations of good building construction, and the latter should receive serious atten tion in the installation of humidifying apparatus. The following conclusions were drawn from the experimental results reported in the aforementioned bulletin: 1. None of the typesof gravity warm air furnace water pans tested proved adequate to evaporate sufficient water to maintain 40 per cent relative humidity in the Research Residence except only in moderately cold weather. 2. The water pans used in the radiator shields tested did not prove adequate to main tain 40 per cent relative humidity in a residence similar to the Research Residence when the outdoor temperature approximated zero degrees Fahrenheit. <See Humidification for Residences, by A. P. Krntz (University of Illinois, Bulletin No. 230). *66 deg is the optimum winter effective temperature recommended by the A.S.H.V.E. Committee on Ventilation Standards. . .. 411