The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Hot Water Suply
It is usually less costly to provide ample storage and smaller heater capacity than to increase the heater capacity so as to reduce the capacity of the storage tank.
35. An estimate of the hot-water requirements for any fixtures necessarily is only an approximate average. However, Table IV has been found to give reasonably safe values of such requirements. The values given in the table represent gallons of water per hour per fixture, and are based on a final temperature of 180° F. To use the table, the hourly hot-water requirements are first found by multiplying the total number of fixtures of each kind by the gallons per fixture required. The total hot-water requirement thus found is multiplied by the hourly heating-capacity factor to obtain the hourly heating capacity required. The hourly heating capacity multiplied by the storage-capacity factor gives the size of storage tank required.
36.An example of the application of Table IV will now be given. Let it be required to select a hot-water storage tank for a residence having 2 lavatories, 2 bathtubs, 1 shower, and 1 kitchen sink. By the use of the table the hourly heating requirement of all hot-water fixtures may be calculated as follows:
2 lavatories require 2x2=4 gallons per hour
2 bathtubs require 2x20= 40 gallons per hour
1 shower requires 1 X 75 =75 gallons per hour
1 kitchen sink requires 1 X 10= 10 gallons per hour
Total 129 gallons per hour
It will be found from the table that the hourly heating capacity factor for a residence is 30 per cent; nence. the hourly heating capacity is 129X.30 = 38.7 gallons per .iour. It Is also found from the table that the storage-capacity factor for a private residence is 70 per cent. Consequently, the storage tank should have a capacity of 38.7X .70 = 27.09 gallons. By consulting Table III it will be found that a tank having a diameter of 12 inches and a length of a little over 41/2 feet, say 5 feet, will satisfy the requirements.
37. The hot-water storage requirements varies widely for different types of buildings. In the case of office buildings, for example, where the principal demand for hot water occurs at noon and again at closing time in the afternoon, the storage capacity required is large as compared to the heating capacity, since there are long periods of low demand during which the heater can be working to bring up the temperature of the water in the tank. In buildings where the demand for hot water is continuous over long periods, as in hospitals, proportionately smaller storage tanks will serve, since high peaks are unusual.
