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HEATING VENTILATING AIR CONDITIONING GUIDE 1944 Table 4. Unit Fuel Consumption Constants (U) for Gas3 Based onO F Outside Temperature, 70 F Inside Temperature, and 8-Hour Reduction to 60 F. Hot Wateb Steam Wabm Ala Heating Value or Gas Btu peb Cu Ft 500 535 800 1000 Cu Ft Gas per Degree-Day per Sq Ft Radiator Up to 500 to 500 1200 Sq Ft Sq Ft Over 1200 Sq Ft 0.142 0.132 0.089 0.071 0.135 0.126 0.085 0.068 0.128 0.120 0.081 0.065 Cu Ft Gas per Degree-Day per Sq Ft Radiator Up to 500 Sq Ft 300 to 700 8q Ft Over 700 Sq Ft Cu Ft Gas per Degree-Day per 1000 Btu Hourly Design Heat Loss Gravity Fan Systems 0.242 0.226 0.151 0.121 0.231 0.215 0.144 0.115 0.220 0.206 0.137 0.110 0.855 0.800 0.534 0.428 0.820 0.766 0.513 0.410 1 Therm 100.000 Btu Gas Consumption in Therms per Degree-Day 1 0.000708 0.000675 0.000642 0.00121 0.00115 0.00110 0.00428 0.00409. Abstracted from Comfort Heating, American Gas Association, 1938. Table 5. Unit Fuel Consumption* Constants (U) for Oil*5 Based on 0 F Outside Temperature, 70 F Inside Temperature, and 8-Hour Reduction to 55 F, .Unit Efpicibnct in Pbh Cent 40 50 60 70 80 Gal Oil per Sq Ft Steam Radiator.. 0.00172 0.00137 0.00114 0.00098 0.00086 Gal Oil per Sq Ft Hot Water Radiator;_ ..... ............................... 0.00108 0.00086 0.00072 0.00062 0.00054 Gal Oil per 1000 Btu per Hour . Heat Loss........ ...... .......................... 0.00715 0.00571 0.00476 0.00409 0.00358 Based on a heating value of 140.000 Btu per gallon. bAbstracted by permission from Degree-Day Handbook (Second Edition. 1937). by C.. Strock and C. H. B. Hotchkiss. Table 6. Unit Fuel Consumption* Constants (U) for CoALb ` Based onOF Outside Temperature, 70 F Inside Temperature, and 8-Hour Reduction to 55 F. Unit. 40 Lb Coal per Sq Ft Steam Radiator.. 0.0200 Lb Coal per Sq Ft Hot Water Radiator...... ............ .............. _....... 0.0125 Lb Coal per 1000 Btu per Hour Heat Loss____ __________ _ 0.0825 ErncizNCT in Per Cent 50 0.0160 60 0.0133 70 0.0114 0.0100 0.0084 0,0072 0.0666 0.0550 0.0471 80 0.0100 0.0063 0.0412 Based on a heating value of 12.000 Btu per pound. bAbstracted by permission from Degree-Day Handbook, (Second Edition, 1937). by C. Strock and C. H. B. Hotchkiss. 232 CHAPTER 11. ESTIMATING FUEL CONSUMPTION Values given in Table 5 assume the use of oil with a heating value of 140.000 Btu per gallon. For other heating values, multiply the values in Table 5 by the ratio of 140,000 divided by the heating value per gallon of fuel being used. Example 6. Estimate the seasonal oil consumption of an oil-fired boiler in a building located in Minneapolis having a calculated heat loss of 192,000 Btu per hour, burning 144.000 Btu per gallon oil and operating at a seasonal efficiency of 60 per cent. The out side design temperature for Minneapolis is --20 F, and the inside design temperature is 70 F. Solution. From Table 5, under 60 per cent efficiency and opposite the bottom column, the value of U is found to be 0.00476 gal per 1000 Btu hourly heat loss for 0 F outside temperature. The correction factor for --20 F outside design temperature from Table 7 is 0.778. Solving, 0.778 X 0.00476 = 0.00370. Making a further correction for the heating value: 0.0037 X = 0.0036 gal per 1000 Btu per hour calculated heat loss per degree- 144,000 day. From Table 3, the normal degree-days for Minneapolis is 7989. Since U is expressed in 1000 Btu, N is equal to 192. Substituting in Equation 4: F = 0.0036 X 7989 X 192 = 5525 gal. Estimating Coal or Coke Consumption Coal or coke consumption estimates are made in exactly the same procedure as for oil. Values of U are given in Table 6 which only apply to inside design temperatues of 70 F and an outside design temperature of OF. A correction must be made for other conditions by use of the multi plying factors in Table 7. Data in Table 6 are based on 12,000 Btu per pound coal and for other heating values of coal they must be multiplied by the ratio of 12,000 divided by the heating value of fuel used. Example 7. A building in Marquette, Mich., has an hourly heat loss at design con ditions of 240,000 Btu per hour. Based on an inside design temperature of 70 F and an outside design temperature of --20 F, what will be the estimated normal seasonal coal consumption for heating if 12,000 Btu per pound fuel is burned at a 50 per cent seasonal efficiency, and what part of the total will be used during November, December, and January? Solution. From Table 6, U is 0.0666 lb of coal per 1000 Btu per hour heat loss. Cor recting for the outside design temperature of --20 F from Table 7, the value of U is 0.778 X 0.0666 = 0.0518. From Table 3, D is 8786 and from the problem N is 240. Substituting in Equation 4: F = 0.0518 X 240 X 8786 = 109,200 lb. Table 7. Correction Factors for Outside Design Temperatures3 FOutside Design Temp. Deg F. Inside Design Temp. Deg -20 -10 0 +10 +20 70 70 70 70 70 Multiplt Values in Tables 4, 5 and 6 bt 0.778 0.875 1.000 1.167 1.400 ttThe multipliers in Table 7. which are high for mild climates and low for cold regions are not in error as might appear. The unit figures in Tables 4, 5, and 6 are per square foot of radiator or thousand Btu heat loss per degree-day. For equivalent buildings and heating seasons, those in warm climates have lower design heat losses and smaller radiator quantities than those in cold cities. Consequently, the unit figure, in quantity of fuel per square foot of radiator per degree-day. is larger for warm localities than for colder regions. Since the northern cities have more radiator surface per given building and a higher seasonal degree-day total than cities in the south, the total fuel per season will be larger for the northern city. 233