TYPICAL INSTALLATIONS UNDERGROUND IN DUCTS Single Conductors         Assumptions: Ambient Temperature 20°C Conductor Temperature 90°C Earth RHO 90°C - cm/watt Concrete RHO 85°C - cm/watt Duct RHO 600°C - cm/watt No Sheath Losses (Single point grounding) 5 Inch Duct Surface Limit 45°C (Direct Buried) * NOTE: Cable surface temperature limit may reduce conductor operating temperature. Three Conductors Paralleled/Triplexed or One-Three Conductor Cable   TYPICAL INSTALLATIONS IN AIR   Assumptions: Ambient Temperature Indoor 40°C - Outdoor 35°C Conductor Temperature 90°C Surface Emissivity 0.85 No Sheath Losses Additional Outdoor Conditions Surface Absorptivity 0.33 Atmospheric Pressure 1 atm Air Speed 4 ft./sec. Derating Factors for Cables in Air Separated by 1/4 to 1 Cable Diameters No. of Cables Vertically No. of Cables Horizontally 1 2 3 4 5 6 2 0.89 0.83 0.79 0.76 0.75 0.74 3 0.80 0.76 0.72 0.70 0.69 0.68 4 0.77 0.72 0.68 0.67 0.66 0.65 5 0.75 0.70 0.66 0.65 0.64 0.63 6 0.74 0.69 0.64 0.63 0.62 0.61 Derating Factors for Cables in Air One Layer of Spaced Cables in a Horizontal Line Separation of Cable Surfaces Derating Factors S Ka 0" 0.840 1" 0.890 2" 0.920 4" 0.960 6" 0.980 8" 0.990 10" 1.00 Derating Factors for Cables in Conduits in Air Separated by 1/4 to 1 Conduit Diameters No. of Conduits Vertically No. of Conduit Horizontally 1 2 3 4 5 6 1 1.00 0.94 0.91 0.88 0.87 0.86 2 0.92 0.87 0.84 0.81 0.80 0.79 3 0.85 0.81 0.78 0.76 0.75 0.74 4 0.82 0.78 0.74 0.73 0.72 0.72 5 0.80 0.76 0.72 0.71 0.70 0.70 6 0.79 0.75 0.71 0.70 0.69 0.68 If the conduits or cables are spaced 10" vertically and horizontally, no correction need be applied in any case. 5kV thru 35kV SINGLE CONDUCTOR CABLE AMPACITIES Copper Conductors Underground in Ducts - One Single Per Duct Direct Buried In Air Conductor Size (AWG/ kcmil) 1 Circuit Fig. 1 Load Factor 2 Circuits Fig. 2 Load Factor 4 Circuits Fig. 3 Load Factor 1 Circuit Fig. 7 Load Factor 2 Circuits Fig. 8  Load Factor   50 75 100 50 75 100 50 75 100 50 75 100 50 75 100 Fig. 11 Indoor Fig. 11 Outdoor 6 121 115 108 115 105 96 105 92 80 161 135 108 156 122 98 118 149 4 158 149 140 149 136 123 136 118 103 211 171 137 204 155 124 155 197 2 209 196 183 196 178 160 176 152 132 266 218 175 257 197 158 206 250 1 239 224 209 224 202 181 201 172 149 305 246 197 294 223 178 237 288 1/0 273 256 237 255 230 206 228 195 168 349 277 223 333 251 201 272 332 2/0 312 292 270 291 261 233 259 221 190 400 312 251 376 283 226 314 383 3/0 357 333 308 332 297 265 295 251 215 458 352 282 424 318 254 361 441 4/0 409 380 350 379 338 300 335 284 243 525 397 318 478 359 286 417 509 250 451 419 385 418 371 329 368 311 265 574 433 347 522 391 312 463 562 350 549 507 465 506 447 394 443 372 316 684 515 412 621 464 370 570 692 500 676 621 566 619 543 477 538 448 380 823 618 493 745 556 443 712 863 750 849 775 703 773 674 588 667 552 464 1010 757 604 912 680 541 907 1082 1000 995 905 818 901 782 680 772 636 534 1162 870 694 1048 780 620 1079 1279 1250 1121 1016 914 1011 873 756 862 706 591 1290 964 768 1162 863 686 1231 1455 1500 1230 1110 997 1105 950 821 938 766 640 1398 1043 831 1258 934 741 1364 1609 1750 1325 1193 1068 1187 1017 877 1003 816 681 1492 1112 885 1340 994 789 1485 1747 2000 1409 1265 1131 1258 1075 926 1060 860 716 1572 1171 931 1411 1046 830 1593 1871 Aluminum Conductors Underground in Ducts - One Single Per Duct Direct Buried In Air Conductor Size (AWG/ kcmil) 1 Circuit Fig. 1 Load Factor 2 Circuits Fig. 2 Load Factor 4 Circuits Fig. 3 Load Factor 1 Circuit Fig. 7 Load Factor 2 Circuits Fig. 8 Load Factor   50 75 100 50 75 100 50 75 100 50 75 100 50 75 100 Fig. 11 Indoor Fig. 11 Outdoor 6 92 88 83 88 81 74 81 71 62 128 104 84 124 95 76 90 118 4 121 114 108 114 105 95 104 91 80 168 133 107 161 121 97 119 157 2 161 152 142 152 137 124 137 118 102 210 169 136 202 154 123 159 197 1 185 173 161 173 156 141 155 134 115 240 191 153 229 173 139 184 228 1/0 211 198 184 197 178 160 177 151 131 275 216 173 259 195 156 211 262 2/0 241 226 209 225 202 181 201 172 148 315 243 195 292 220 176 243 302 3/0 276 258 238 257 230 205 228 194 167 361 274 220 330 248 198 281 349 4/0 317 295 272 294 262 233 260 220 188 409 309 247 372 279 223 324 403 250 350 325 299 324 288 255 286 241 206 447 337 270 406 304 243 360 447 350 427 394 362 393 348 307 344 289 246 534 402 321 484 362 289 445 549 500 527 484 442 483 424 372 419 350 296 644 483 386 583 435 346 558 687 750 670 612 555 609 531 463 524 434 5kV thru 35kV TRIPLEXED OR PARALLELED CABLE AMPACITIES SINGLE CONDUCTORS Copper Conductors Underground in Ducts - Three 1/C Cable Per Duct Direct Buried Three 1/C Cable Per Circuit In Air Three Singles Conductor Size (AWG/ kcmil) 1 Circuit Fig. 4 Load Factor 2 Circuits Fig. 5 Load Factor 4 Circuits Fig. 6 Load Factor 1 Circuit Fig. 9 Load Factor 2 Circuits Fig. 10 Load Factor   50 75 100 50 75 100 50 75 100 50 75 100 50 75 100 Fig. 12 Indoor Fig. 12 Outdoor 6 101 97 92 97 91 84 91 81 73 139 114 92 135 104 83 101 130 4 131 125 119 126 117 108 117 105 93 182 146 117 175 132 105 133 171 2 174 166 156 167 154 141 154 136 120 234 189 152 224 170 136 179 219 1 199 189 178 190 175 160 175 154 135 268 214 172 254 192 153 205 252 1/0 227 215 202 216 199 181 198 174 153 306 242 194 287 216 173 235 289 2/0 259 245 230 246 226 205 225 197 173 351 273 219 324 244 195 270 332 3/0 295 279 261 280 256 233 256 223 195 402 308 247 366 275 220 311 382 4/0 337 317 297 319 291 264 290 253 221 460 349