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HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Estimating Coal or Coke Consumption Coal or coke consumption estimates cari be made in exactly the same way as for oil. The uncorrected values of U are given in Table 7. These constants apply only to inside design temperatures of 70 F and an outside design temperature of 0 F, and correction must be made for other con ditions by use of the multiplying factors in Table 5. Table 7 is based on 12,000 Btu per pound coal and for other heating values of coal, values in Table 7 must be multiplied by the ratio of 12,000 divided by the heating value of fuel used. Example 9. A building in Marquette, Mich., has an hourly heat loss at design con ditions of 240,000 Btu per hour. If the inside design temperature is to be 70 F and the outside design temperature is --10 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 7, U uncorrected, is 0.0666 lb of coal per 1000 Btu per hour heat loss. Correcting for the outside design temperature, Table 5, the corrected value of U is 0.875 X 0.0666 = 0.0583. From Table 3, D is 8721 and from the problem N is 240. Substituting in Equation 3: F = 0.0583 X 240 X 8721 = 122,024 lb. Fuel used over any period is, according to the theory of the degree-day, proportional to the number of degree-days during the period. From Table 3, the average number of <legree-days for November, December, and January in Marquette are 951, 1314, and 1510, a total of 3775. The yearly total is 8721, so that during these three months the estimated consumption is: 3774 X 122,024 = 52,820 lb. Estimating Steam Consumption In estimating steam consumption the efficiency is not ordinarily a factor and is assumed at 100 per cent. Ordinarily low pressure steam with a heating value of 1000 Btu per pound is used so that no correction is necessary for heating value in the usual case. In comparing values from different cities, correction should be made for design temperature (see Table 5) when the unit figures are in terms of square foot of radiator or 1000 Btu per hour calculated heat loss, but not when the values are in terms of building volume or floor space. Consideration has been given to the difference in steam utilization of different types of buildings and Table 84 shows actual average units for these various types. These figures are obtained from operating results in 196 buildings located in 21 different cities in the United States. Being averages, and for small groups in each type, the figures may need con siderable modification to allow for local variations. It should be especially noted that the steam used for heating hot water is included in the values given in Table 8, but in the case of office buildings, the steam for heating only is also shown. Presentation of the unit consumption in three ways permits making the estimate if either the calculated heat loss or the volume of net heated space in the building is known. . 4The Heat Requirements of Buildings, by J. H. Walker and G. H. Tuttle (A.S.H.V.E. Transactions, Vol. 41. 1935, p. 171). 218 CHAPTER 10. HEAT AND FUEL UTILIZATION Table 8. Steam Consumption for Various Classes of Buildings'1 (Heating Season Only) Building Classification Apartments...................... Hotels.--------------- --------Residences...... .................. Printing-----------.......... Clubs and Lodges........... Retail Stores.................... Theaters.--...................... Loft and Mfg..... ............ Banks...... ------------- -----Auto Sales and Service.. Churches--..... -------------Department Stores--...... Garages (Storage)'------Offices (Total)...... ........... Offices (Heating only).... No. OF Buildings Listed Steam Consumption Pounds peb Degeee-Dat--65 F Basis'* Per M Cu Ft Per M Sq Ft Per M Btu of Heated of Radiatorc per Hr of Space Surface Heat Lofflb 16 1.78 97.5 0.359 10 1.46 80.6 0.371 12 1.32 64.2 7 1.25 105.5 10 0.96 77.0 18 0.90 80.6 0.268 .6 0.90 75.0 0.498 16 0.89 72.3 0.283 7 0.88 45.2 --------- 8 0.83 62.2 6 0.58 49.4 14 0.57 60.7 0.238 6 0.42 72.3 ______ 35 , 1.09 70.0 0.283 35 0.975 65.4 0.256 alndudes steam for beating domestic water for heating season only. bHeat loss calculated for maximum design condition (in most cases 70 F inside, zero outside), cEquivalent steam radiator surface. dThe figures are a numerical--not a weighted--average for the several buildings in each class. Based on zero consumption at 55 F. Example 10. A store in Detroit with a heating system designed to maintain 70 F inside in 0 F weather has 1700 sq ft of equivalent direct steam radiator surface, and uses only moderate quantities of hot water. What would be the estimated average yearly steam consumption of purchased steam for heating and for hot water during the heating season? Solution. According to Table 8, a store (0 to 70 F conditions) would use 80.6 lb of steam per thousand square feet of radiation per degree-day, including winter hot water. From Table 3, Detroit has 6460 degree-days per normal year. Inserting in Equation 3: F * 80.6 X 1.7 X 6460 = 885,149 lb of steam. Table 9. Building Load Factors and Demands of Some Detroit Buildings21 Building Classification Hotels..............._ ........................................................... Offices.................................................... .....^.................... Apartments.................................................... ..... Retail Stores................................................................... Banks.................... Churches....................... .................... ...... Department Stores........................................................ Theaters........................ ........ Load Factob Lb of Demand peb Hb peb Sq Ft op Equivalent Installed Radiatob Surface 0.318 0.316 0.287 0.263 0.255 0.238 0.223 0.203 0.158 0.138 0.126 ~~ 0.184 0.207 0.217 0.209 0.225 0.182 0.248 0.158 0.152 0.145 0.151 Report of Commercial Relations Committee. Proceedings, National District Healing Association. 1932. 219 <8 ;!: j 'j \t | 'i !! j' I 1 ! ;