Document RJr9pYaVOOaxbOQxbqdLpqJKz

250 CHAPTER 18 1959 Guide Table 7.... Required Size of Extended-Plenum Cfm Handled by Ffeaum Pteaom Dtmeoaoft* inches Cfo Handled by Plenum Plenum Dimenmm Inches Up to 300 301 to 400 401 to 500 501 to 600 601 to 700 8x8 10x8 12 x 8 14 x 8 16 x 8 701 to 800 SOI to 900 901 to 1000 1001 to 1100 1101 to 1200 20x8 22x8 24x8 28 x 8 28x8 joins the trunk the required increase shown in the last line of Table 9 or Table 10 refers to an 8-in. trunk duct. Where two branches form a trunk the longer branch is considered to be the trunk and its equivalent width (for 8-in. depth) is increased as required. DESIGN PROCEDURE FOR LARGE SYSTEMS' for buildings having a heat loss in excess of 120,000 Btu per hour, the design procedure given in Manual 9 of the National Warm Air Heating and Air Conditioning Associa tion, may be used. Work sheets 9a, 9b, and 9c are available to simplify calculations.'- The procedure consists of: 1. Calculation of design heat losses from individual spaces in the structure. The calculation of these losses is explained in Chapter 12. 2. Location of registers and return intakes on floor plan, shoeing types of registers, with distance from register to op posite wall and deflection of registers desired. 3. 'Laying out a proposed duct system for both warm air and return air sides of the system, and including details of types of fittings and the actual and equivalent lengths of each branch line from bonnet to register, without sixes. (See Fig. 7, Groups 1 through 6, for equivalent length of fittings.) 4. 'Determination of bonnet temperature. If the rating sheet for a furnace-blower unit specifies a fixed value of bonnet temperature, find this temperature in the left-hand column of Table 11. If not specified, use the following procedure: Use Table 11 for buildings having a heat loss be tween 120,000 and 350,000 Btu per hr, or Table 12 for buildings having a heat loss greater than 350,000 Btu per hr. Select short est actual length, including vertical risers and read downward in nearest column in Tables 11 or 12 until lower heavy diagonal line is reached, but do not cross line. Run borixontally to first column of table and note bonnet temperature. Also select long est actual length including vertical risers, and read downward in nearest column in Tables 11 or 12 until upper heavy diagonal line is just crossed. Run horizontally to left to obtain value for bonnet temperature in first column. Select as the design bonnet temperature any value between these two limits. 5. Determination of air volume to be delivered through each reester and the respective register air temperatures. Using Tables 11 or 12 and the design bonnet temperature selected, find the values of cfm per 1000 Btu for each* duct length, and the corresponding register temperature. 6. Selection of register sixes and pressure losses to produce necessary throw, for the air volumes handled. Use Tables 13 or 14 to obtain required free area and pressure loss of register. Tables 15 and 16 are used in sizing the duct system. 7. Design of duet system. A. Warm air branches. a. Use Table 16 to select maximum bonnet pressure usually required for the trunk carrying the maxi mum volume of air (cfm). If the maximum bonnet pressure is not high enough to accommodate the ressure loss through the registers, use a higher onnet pressure. If tne register pressure is critically large, it may be necessary to reduce it by either using two registers in place of one, or using smaller deflection angles. b. Obtain actual duct loss by subtracting total register fressure loss, as determined from Tables 13 or 14, rom maximum bonnet pressure, c. Obtain the pressure drop in each duct per 100 ft by use of Table 15. ' d. Determine duct sise by means of air friction chart ' (such as Fig. 2, or Fig. 3, Chapter 21), volume (cfm), and pressure drop per 100 ft of duct. B. Return air branches. (Continued on p. 253.) Actual ft Table 8.... Required Size of Return Air Grille and Duct For Pressure Drop Allowance of 0.05 In. of Wafer Up to 10 Pf n to 20 Ft 21 to 30 FI 31 to 40 Ft GriBe Free No. of 90 Oeg lums. Bfuft 1 2 3 4 5. 6 1 23456 1 234561 Oucf Frew Area 6 16 5,000 14 17 20 23 28 28 15 19 22 25 27 28 17 20 23 25 27 29 18 31 24 27 28 30 32 10,000 27 32 37 42 46 49 29 34 39 43 47 49 31 36 41 45 48 51 33 38 43 47 49 51 47 15,000 37 44 50 55 60 64 40 46 52 57 61 65 43 49 54 58 63 67 45 51 56 61 64 67 63 20,000' 46 54 61 66 73 78 49 57 63 69 75 79 53 60 65 71 77 82 55 62 68 74 78 83 79 25,000 54 64 72 79 86 92 58 68 75 82 88 94 62 71 78 84 91 96 66 74 80 87 92 98 95 30,000 62 73 82 89 97 104 67 76 85 93 100 106 71 80 88 95 102 108 75 84 91 99 104 110 111 35,000 69 82 92 101 111 119 74 85* 95 106 114 121 79 91 99 108 117 124 84 94 103 113 119 126 no126 40,000 77 90 100 121 130 82 94 105 116 124 132 87 99 109 118 128 137 92 103 113 123 130 140 158 50,000 89 105 119 132 146 158 95 111 124 138 150 161 102 117 129 142 155 166 10$ 123 135 148 158 170 190 60,000 100 122 139 154 170 181 111 129 145 161 174 184 119 137 151 165 178 189 126 143 158 172 181 193 221 70,000 117 139 158 174 191 203 127 147 164 182 195 206 135 155 171 186 200 213 144 162 178 193 203 216 252 80,000 128 155 175 191 208 222 140 164 182 198 214 225 151 172 188 203 219 231 160 179 195 211 222 235 284 90,000 141 168 188 205 225 244 153 177 195 213 232 248 164 186 201 218 240 256 173 193 209 229 244 262 316 100,000 154 180 200 221 247 285 166 189 209 233 252 270 176 198 217 239 258 277 185 206 227 250 265 285 Note: Where s multipU number<d return sir darts join together, add the mdiridnal duct free areas toerther to determine the tree area of dort to be used from that paint to the return air plenum of furnace. Warm Air Heating Systems 251 fqwr. Uflgtfi of RHhgs end Registers Cot. a Up to 70 Eq Ft Table 9.... Capacity and Sizing Table--First Story for Worm Air and Retorn Air Stock, Brandi, and Registers Horizonte! length Furnace to Register ___ Iraidated | Attic Ducts firsf Story Room Hoof Loss--fifuh Col. b . CoLc CoL d CoL CoL f CoL g CoL b Up to 7 8-12 13-17 18-25 28-35 36-45 46-55 Up to 5 6-9 10-13 14-18 19-25 26-35 36-45 46-55 7,200 6,700 6,100 5,600 4,800 4,100 3,500 3,000 12,500 11,700 10,800 9,900 8.500 7.400 6.400 5.500 16,000 15.000 14.000 13.000 11.000 9,900 8.700 7.700 19,100 18,000 - 17,000 16,000 14,200 12,500 11,000 9,600 25.000 23,400 21,600 19.800 17.000 14.800 .12,800 11.000 CoL 1 32.000 30.000 28.000 26,000 22,600 19,800 17.400 15.400 CL j 80,000 75.000 70.000 65.000 56.500 49.500 43.500 38.500 71 to 100 Eq Ft Up to 7 8-12 13-17 18-25 26-35 36-45 46-55 Up to 5 6-9 10-13 14-18 19-25 26-35 36-45 46-55 5.500 5,100 4,800 4.500 3,900 3,400 3,000 2,600 9,900 9.200 8,600 8,100 7,100. 6.200 5,400. , 4,600 13,100 12,300 11,600 10,900 9,700 8.500 7.500 6.500 16,300 15,400 14,500 13,700 12,200 10,800 9,500 8,300 19.800 18.400 17.200 16.200 14.200 12.400 10.800 9.200 28,200 24,600 23,200 21,800 19,400 17.000 15.000 13.000 65.500 61.500 58,000 54.500 48.500 42.500 37.500 33.500 101 to 130 Eq Ft Up to 7 8-12 13-17 18-25 26-35 36-45 46-55 Up to 5 6-9 10-13 14-18 19-25 26-35 36-45 46-55 4,600 4.300 4,100 3,800 3.300 3,000 2,700 2.300 8,500 7.900 7,400 6.900 6,100 5,300 4,700 4,000 11,300 10,600 10,000 9.400 8.400 7.400 6,500 5.400 14,300 13.500 12,700 11,900 10.500 9.300 8.300 7,000 17,000 15.800 14.800 13.800 12,200 10,600 .9,400 8,000 22,600 21,200 20,000 18,800 16,800 14.800 13,000 10.800 56.200 52,600 50.200 47,300 42.000 37.000 32,400 27.000 131 to 165 Eq Ft Up to 7 8-12 18-17 18-25 26-35 36-45 46-55 Up .to 5 6-9 10-13 14-18 19-25 26-35 36-45 46-55 4,100 3,800 3.600 3,400 2,900 2.600 27300 2,000 7.300 ` 6,900 6,400 6,000 5.300 4,700 4,200 3,600 9,800 9.100 8,600 8.100 7,200 6,400 5,600 4,700 12.300 11,700 11,000 10.300 9.100 8.100 7,100 6,000 14.600 13.800 12.800 12,000 10.600 . 9,600 8,400 7,200 19,600 18,200 17.200 16.200 14,400 12,800 11,200 9,400 49,200 45.800 41,900 40,300 36,000 31.800 28,100 23,500 166 to 200 Eq Ft Up to 7 8-12 18-17 18-25 26-35 36-45 46-55 Combination Number Up to 5 6-6 10-13 14-18 19-25 26-35 36-45 46-55 3,800 3,500 3,300 3.100 2.700 2,400 2.100 1.700 41 6,500 6,100 5,700 5,400 4.800 4,300 3.800 3,000 42 8,800 8,200 7.700 7,200 6,400 ' 5.700 5,000 3,900 43 11,000 10,500 9,900 9.300 8.300 7.300 6,400 5,100 44 13,000 12,200 11,400 10,800 9.600 8,600 7.600 6,000 45 17,600 16.400 15.400 14.400 12,800 11.400 10,000 7,800 46 44.100 51.500 38,800 36.000 32.000 28,200 24,700 19.500 47 Stacks1*: No. (in parenthesis) and Sixe Rectangular Branch Size Round Branch Size (Diam) (1) 10x3)< (1) 10x3H (1) 12x3>< (1) 14x3*i (2) I0x3',i (2) 12x3& 3x8 4x8 5x8 6x8 8x8 10x8 5 6 7 8 9 10 - 15x8 12 Number of Joist Spaces and Minimum DepthReturn Air Registers: Low Wall, High Wall, or Baseboard 1 at 3 10x6 1 at 3 10x6 1 at 4 12x6 1 at 5 14x6 1 at 6 or 2 at 3 (2)10x6 or (1) 24x6 1 at 7 or 2 at 4 (2)12x6 or (1) 30x6 1 at 9 or 2 at 5 -- Registers: Floor-Warm Air 8x10 8x10 9x12 9x12 or longer 10x12 12x14 -- Registers: Floor-Return Air 6x10 or 6x10 or 6x12 or 4x14 4x14 6x14 6x14 6x30 6x30 8x30 Trunk Duct Increase, Inches 1 2 3 4 5 7 12 * Uninsulated duet* in heated (pace* and insulated dticta in apaeee. Note: For return air a 14xSH to. etud apace may be need instead of IueSM in. ataek. Where I2x3H in. or 11x3M in. stack i* required, a 14x3H in. stud apace may be used only what inside of etud space i> smooth and without protruding plaster keys. The number of joist spaces for combination <7 i# based on txS in. joists. One pace may be used with 2x10 in- joutt- Tbe limiting factor for a duet combination is the stack capacity.