174 



ANNUAL. REPORT SMITHSONIAN INSTITUTION, 1939 



If the family is considered as equivalent to four or five adults, thai 

 average total daily hot-water demand is approximately 20 to 25 gal- 

 lons per person. This figure, though much greater than the accepted 

 rural average, is only 50 to 60 percent of the demand recommended 

 by the American Society of Heating and Ventilating Engineers for 

 apartment houses. Nevertheless, the observed total coincides with 

 the general recommendations of a manufacturer of commercial solar 

 water heaters. 



Recognizing that the figures in table 1 represent neither a scanty 

 nor an extravagant use of hot water, one notes that 58l^ gallons of 

 hot water is needed in the first 3 hours on wash days (three times 

 a week) ; then only I414 gallons is used in the following 5I/2 hours, 

 with no demand at all for the next 31/2 hours. Then another heavy 

 demand of 49i/^ gallons of hot water comes with the evening baths, 

 usually within 3 hours. Obviously, the solar heater cannot meet 

 the first demand of 60 gallons early in the morning without an insu- 

 lated tank to keep hot the water heated the previous day. Since, fur- 

 thermore, the evening baths will be taken from this storage of hot 

 water needed in the morning, the storage tank should be large enough, 

 as a general rule, to hold the entire day's requirement. 



Table 1. — Daily Hot-Wateb Demand fob a Family of 5 



Time 



Use 



Temperature, 

 degrees F. 



Quantity of hot 

 water, gallons 



7:00 a.m 



8:00-8-30 a. m 



8:30-9:15 a. m 



9:30 a. m... 



9:15-10:00 a. m 



10:00 a. m 



10:15-11:30 a. m 



11:30 a. m.-3:30p. m.. 



7:00-7:30 p. m 



7:30-8:30 p. m 



8:30 p. m.-6:30a. m... 



Shavlng and incidental 



Clothes washing, 1 maehineful reused. . 



Dishwashing _ - 



Washing clothes by hand in sink 



4 trays rinse water 



Baby's bath 



Incidental-- 



Washing dinner dishes and incidental. 



2 children's baths 



Washing supper dishes.. 



2 adults' baths. 1 



100 

 128 

 128 

 120 

 100 

 100 



125 



92 



»125 



95 



4, plus cold blend. 



14. 



12. 



Z14, plus cold blend. 



22, plus cold blend. 



3, plus cold blend. 



3. 



25, plus cold blend. 



7. 



17}^, plus cold blend. 



Washday total 



Average daily total. 



122H gallons hot water 

 96 gallons hot water 



' An electric dishwasher requires 150° water to sterilize, but water 160° F. or hotter causes trouble. The 

 total quantity including the preliminary spray (waiting for water to run hot) averages 5 or 6 gallons per 

 charge. Usually an additional 3 gallons is used simultaneously for washing pans and for incidental clean- 

 ing up. 



INSTALLATION AND CONSTRUCTION OF SOLAR WATER-HEATER 



SYSTEMS 



In suitable locations in the South and West a solar-heater system 

 properly designed and installed will by itself adequately furnish 

 hot water continually throughout the summer for domestic use. 

 In the winter, however, some auxiliary means for heating water 

 is usually desirable. 



