Document 6BQ9kqQLwzgvo8wvBz26Nn8v9

240 CHAPTER 12 1954 Guide 1 outdoor air supply equals or exceeds the amount of natural infiltration which would 1 occur without ventilation, the natural infiltration may be neglected. ' 9. The sum of the heat losses by transmisions (Item 6) through the outside walls and glass, as well as through any cold .floors, ceilings or roof plus the heat equivalent (Item 7) of the cold air entering by infiltration, or required to replace mechanical exhaust, represents the total heat loss equivalent for any building. . 10. In buildings which have a reasonably steady internal heat release of appre ciable magnitude from sources other than the heating system, a computation of this heat release under design conditions should be made for deduction from the total of the heat losses computed in items 1-9. This is especially important for heating sys tems of high initial cost or those for which a demand charge is based on installed capacity. DESIGN OUTDOOR WEATHER CONDITIONS There are no hard and fast rules for selecting the design outdoor weather conditions to be used for a given locality or type of building or heating system, and the selection is to some extent a matter of judgment arid experience. The appropriate design temperature in a given locality may vary with heat capacity and degree of insulation of a particular structure, the amount of . protection from the wind, the length of time that nightly minimum tempera tures persist, whether the particular building is being used day and night, and perhaps other factors. For heating systems that depend primarily on electrical energy as a source of heat it will often be desirable, for economic reasons, to make a more careful analysis of the factors that affect design . weather conditions than would otherwise be justified. The outside design temperature seldom is taken as the lowest tempera- . ture, or even the lowest daily mean temperature ever recorded in a given locality. Such temperatures rarely recur in successive years. Likewise the wind direction and velocity occurring at the time of design outside temperature may be different from the average velocity and prevailing direction during the. winter. The A.S.H.V.E. Technical Advisory Committee on Weather Design . Conditions has recommended the adoption for heating load calculations , of an outside design temperature which is equalled or exceeded during 97\ percent of the hours in December, January, February and March. Complete design temperature data based on this formula are not available, but Col- umn 8, Table 1, lists this recommended design temperature based'on airport station readings for the period indicated, generally the five years, 1935- \ 1939. In most cases these stations are outside of the city and these data apply primarily to rural areas. In general the use of the airport data for buildings within an adjacent city will not make an appreciable difference in : design load. is. Because of the limited data available in Column 8 of Table 1, design V temperatures in common use are listed in Column 10. Many of those,,, values were furnished by A.S.H.V.E. members, the remainder were taken from an ACRMA Bulletin,1 manufacturers' publications, and other sources,V. and a few were estimated. -- 15 The map in Fig. 1 shows isotherms of outdoor winter design temperature ; which are based on the values in Column 10 of Table 1 with some modifica tions where other data indicated that Column 8 furnishes a more reasonable design temperature. These isotherms have also been modified slightly in'V. accordance with the elevations of the various cities. The isotherms are ;.v drawn on 10 deg temperature intervals, in most cases, and are so placed that interpolation between isotherms will provide the proper design temper-^' ature for cities between the isotherms. Thus, a city located half-way be- Heating Load } a; -241 Table 1. Winter Climatic Conditions* . . Col. Col. 3 Col. 4 ElzVATION Record*1 FT Col. 5 1 Col. 6 Col. 7 I Col. 8 Low- 1 Aver- {Design EST Temp. on ' Rec ord F AGE Avg. . An- WinNTTAL TEH Min. Temp/ Trptrp ' F DbtBulb m% i Basis* j 9 Col. 0 Col. 11 DesigN . A vo. " B "b Wind T"- Vel. ph,, IN. Dec!* COMVp Use* Feb/ h *F Mpn Birmingham............ A Mobile............ ........ c. Mobile.:...................A. Montgomery........... .c . Montgomery............."a Aria,,.. Flagstaff............ q Kingman___ .....A Phoenix...................''c Phoenix........... ]' a Tubson.............. *''*`c Ark... Tucson..................* a Winslow............. C Winslow........... a Yuma............... c Fort Smith............ C Fort Smith. a Little Rock............ C Cal.. Little Rock.............. A Bakersfield___ ....A Burbank........... * * A ~ gossett.........i ibureka.................... c Fresno................ q fresno................. :::;a "Os Angeles..............C Oakland....... a Bed Bluff................ \q Red Bluff......... a Redding......... A fcacramento............ C Sacramento_ A gap Diego................. G gan Diego................. A gan Francisco... C 1 ..................... C 1 Col.... "Iliams.. A1 Denver..& env?r-.......................A 52 wand Junction. . C 45 EUe!> *..........................C 47 Conn. Hartford..... r* | Hartford...... .....A New Haven_ C D.C.. Fla.... Haven.............A Washington..............c J^shington.............. A Apalachicola.......... C Jacksonville.. C :;;a o 1 1 li | Mmi ........ Y Pensacola............ a ??Saco'*............... ..A * p 11 1893-1947 1893-1945 1939-1947 1872-1947 -10 -10 -1-10 1940-1947 13 1872-1947 1938-1944 1899-1947 1935-1939* 1895-1947 1937-1947 Up to 1948 1935-1939d Up to 1946 1932-1947 1876-1946" -5 9 -25 8 16 21 6 19 -19 -18 22 1882-1945 1945-1947 1879-1942 -15 7 --12 1942-1947 1937-1946* 1931-1947 7 19 21 1935-1939* 1886-1947 20 1887-1939 17 1939-1947 1877-1947 23 28 1929--1947 23 1877-1934 17 1944-1947 25 1935-1939* 17 1877-1947 17 1938-1947 22 1871-1940 '1939-1947 1875-1947 Up to 1946 25 34 27 22 1935-1939* 1871-1947 -29 1934-1947 -30 1889-1945* -21 1889-1938* -27 1939-1947 -26 1905-1940 -18 1940-1947 -24 1872-1946* -15 1943-1947 -4 1871-1947 -15 1935-1939* 1922-1947 18 1871-1947 10 1938-1947 26 1871-1947 41 1939-1947 42 1896-1947 27 1940-1947 28 1879-1947 7 1943-1947 20 18 19 -15 52.3 53.8 61.8 58.9 56.4 35.9 59.5 57.7 57.2 57.2 43.6 43.5 62.5 50.4 1.6 55.5 57.5 49.3 53.8 59.3 51.9 53.9 21 33 35 27 53.0 58.2 37 54.2 53.5 39.0 37.0 39.9 41.1 36.4 29 62.0 60.6 73.1 72.5 71.4 59.7 45 Ga... JJmipa.... ai If*...:............ 5 Augusta............... q Augusta............... X Macon... r- Macon. ....................? ,o 42 % 4; J890-1940* 1941-1946 1935-1939* 1878-1945* 1871-1946* 1939-1947 1899-1947 19 31 66.0 61.3 54.2 ' 54.7 38 22 Savannah..'.:;"' c lli 1939t1947 Idaho.. Savannah.............a fe............... - . C 5 28l! 111.... Pocatello .::.......... 8 4522 cZMI.............S A 4467 chicago 8; iii Hlank 1871-1945 1939-1947 1864-1939* 1939-1947 1935-1939* 1935-1939* 1900-1944 1899-1947 1938-1947 i 1872-1947 :Up to 1946 16 -28 -13 -35 -18 -23 -28 -23 -16 -23 1 -12 58.5 56.7 40.3 39.8 .36.9 42.7 37.1 35.0 46.4 37.6 29 5 2 -7. ^es indicate data not yet completed. 8.5 5.6 6.3 7.5 6.6 .5.6 4.9 5 10 15 10' -10 25 25 -10 30 10 5 25 8.0 9.9 7.5 7.7 5.4 5.2 6.7 8.3 8.3 4.5 7.5 7.1 5.8 8.3 .8.8 6.4 8.3 8.1 7.4 7.0 30 ; , -26; .35 30 7.3 5.4 6.4 6.1 30 35 35 25 -10 -15 -20 0 0 0: 25 25 45 7.2 6.3 7.5 7.5 4.4 7.9 8.7 9.4 7.8 8.4 9.0 10.6 35 10.1 7.3 20 10.9 6.5 10.2 30 . 8.6 - 10 11.7 10 6.5 15 6.7 7.7 -55 4.1 8.9 7.2 0 -10 12.0