Document RpGGM33ODk5DaO5e8vo9oXpGn

462 CHAPTER 18 1957 Guide I deg. below 65 F. For any one day, when the mean temperature is less than 65 F, there are as many degree-days as there are degrees difference in temperature between the mean temperature for the day and 65 F. De gree-days may be calculated on other than the 65 F base for use mainly for warehouse and other industrial spaces in "which temperatures to "be maintained are considerably below the 68 to 72 F range. They are listed in a later section of this chapter. Studies made by the National District Heating Association11 of the metered steam consumption of 163 buildings located in 22 different cities and served with steam from a district heating company, substantiate the approximate correctness of the 65 F base chosen by the gas industry. Table 2 lists the average number of degree-days which have occurred over a long period of years, by months, and the yearly totals for various cities in the United States and Canada. The number of degree-days for United States cities were calculated by taking the difference between 65 F and the daily mean temperature computed as half the total of the daily maximum and the daily minimum temperatures. The monthly averages were obtained by adding daily degree-days for each month each year and dividing by the number of days in the month; then totaling the respective calendar monthly averages for the number of years indicated and dividing by the number of years. The total or long term yearly average degree-day value is the summation of the 12 monthly averages. Degree days for Canadian cities were supplied by the Canadian Meteorological Division of the Department of Transport, and were computed from the mean tem perature normals on record for the various stations. (See Note c, Table 2.) Any attempt to apply the degree-aay method of estimating fuel con sumption for less than one month would be of very little value. It should be noted that this method of calculation is based on a long term average and cannot be expected to coincide with any single year in calculating fuel requirement. Individual yearly degree-day calculations may vary as much as 20 percent above and below the long term average. If the degree-days occurring each day are totaled for a reasonably long period, the fuel consumption during that period as compared with another, period will be in direct proportion to the number of degree-days in the two periods. Consequently, for a given installation, the fuel consumption can be calculated in terms of fuel used per degree-day for any sufficiently long period, and compared with similar ratios for other periods to determine the relative operating efficiencies with the outside temperature variable eliminated. Computation and Application The general equation for calculating the probable fuel consumption by the degree-day method is: F=UXNxDxCt (4) where F = fuel consumption for the estimate period. V = unit fuel consumption, or quantity of fuel used per (degree-day) (building load unit). N * number of building load units (when available use calculated hourly heat loss instead of actual amount of radiation installed). D = number of degree-days for the estimate period. Ct = temperature-correction factor from Table 3. Values of N depend on the particular building for which the estimate is Estimating Fuel Consumption for Space Heating 463 Table 2. Average Monthly and Yearly Degree-Days fob Cities in the United States and Canada** b* 0 (Base 65F) 1Nov. I eo.D F ed. Apr. M at State Station No. f EARS OP Sea >jD sons *-> 6D < ta OQ d O z< e<s S a Z P- Ala-- Anniston............ A Birmingham...... t Mobile................/ Mobile................. C Montgomery...... / Montgomery...... C Arix... Flagstaff............./ Phoenix ............. A Phoenix.............. C Yuma.................. A Ark... Bentcmville........... 08/07-40/4; Fort Smith......... A Little Rock........ A Calif.. Eureka................C Fresno................. A Independence....... 98/90-40/41 Los Angeles....... A Los Angeles....... C Needles.................. 17/18-38/3S Point Reyes......... 98/99-40/41 Red Bluff...........A Sacramento........ A Sacramento.........C San Diego...........A San Francisco... A San 1* rancisco C San Jose..............C Colo... Denver . A Denver.............. C Durango. . 04/05-40/41 Grand Junction A Leadville. . 07/08-40/41 Pueblo............... A Conn. Hartford........... A New Haven... .A D. C... Washington . A Washington........ C Fla.... Apalachicola.......C Jacksonville___ A Jacksonville... C Key West............A Key West.......... C Miami... A Miami... C. Pensacola. C lampa............. A Atlanta... A Atlanta........ C Auguste___ A Macon....... A Savannah A 1 homasvillft Boise....... >5/06-40/41 A Lewiston. A Pocatello A Cairo ... n Chicago............... A 35 43 22 43 3? 34 36 Ind__ r-- Springfield.......... A Springfield........ C Evansville. A rort Wavnpi A Indianapolis___ A Indianapolis O Royal Center . 18/19-31/32 T^eHaute....... A Charles City...... C 5LTe"Prt.......... C Des Moines A Uea Moines___ C S"b,usuo............ 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TUTninteltd.j States cities from a publication of the United States Weather Bureau, Monthly NorUiures, PPrreecciippiittaattiioonn aanndd RDemgtreme DDaatyl*s, 1199.5U4 aamre ffoorr tt.hhe npaerriino^d 11099211 ttoo I1Q9.5V0I iinnncll.uiMsivAe. TTHhoosoea data are tHm! 01 `or which yeare are given in Column 3 are not listed in the above publication and the with the wuc" were computed by the United States Weather Bureau in 1948 and 1947 in accordance b quirements the National Joint Committee on Weather Statistics. e .op airport stations. A, and city stations, C, are both given where available, norma] mom Sjna<han cities were oomputed by the Meteorological Division, Department of Transport from Thom, The t? .cnea,n temperatures, adjusted for the summer months by a method described by H. C. S. Vnl v?111 Relationship between Heating Degree Days and Temperature, Monthly Weather m` * No. 1, January, 1954.