16 − Vent connectors serving Category I appliances shall | two consecutive table size diameters over the size of | |
not be connected to any portion of mechanical draft | the draft hood outlet or flue collar outlet. | |
systems operating under positive pressure such as | 20 − Do not install a manual damper, barometric draft regu- | |
Category III or IV venting systems. | lator or flue restrictor between the furnace and the | |
17 − If vent connectors are combined prior to entering the | chimney. | |
common vent, the maximum common vent capacity | 21 − When connecting this appliance to an existing dedi- | |
listed in the common venting tables must be reduced by | cated or common venting system, you must inspect the | |
10%, the equivalent of one 90° elbow (0.90 x maximum | venting system’s general condition and look for signs | |
common vent capacity). | ||
of corrosion. The existing vent pipe size must conform | ||
| ||
18 − The common vent diameter must always be at least as | to these instructions and the provided venting tables. If | |
large as the largest vent connector diameter. | the existing venting system does not meet these re- | |
19 − In no case, shall the vent connector be sized more than | quirements, it must be resized. |
TABLE 3
Capacity of Type B Double−Wall Vents with Type B Double−Wall Connectors
Serving a Single Category I Appliance
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| Vent and Connector Diameter − D (inches) |
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Height | Lateral |
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| 3 Inch |
| 4 Inch |
| 5 Inch |
| 6 Inch | ||||||
H | L |
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| Appliance Input Rating in Thousands of Btu Per Hour |
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(feet) | (feet) |
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| MIN |
| MAX | MIN |
| MAX | MIN |
| MAX | MIN |
| MAX |
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| 0 | 0 |
| 78 | 0 |
| 152 | 0 |
| 251 | 0 |
| 375 |
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| 2 | 13 |
| 51 | 18 |
| 97 | 27 |
| 157 | 32 |
| 232 |
6 |
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4 | 21 |
| 49 | 30 |
| 94 | 39 |
| 153 | 50 |
| 227 | |
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| 6 | 25 |
| 46 | 36 |
| 91 | 47 |
| 149 | 59 |
| 223 |
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| 0 | 0 |
| 84 | 0 |
| 165 | 0 |
| 276 | 0 |
| 415 |
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| 2 | 12 |
| 57 | 16 |
| 109 | 25 |
| 178 | 28 |
| 263 |
8 |
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5 | 23 |
| 53 | 32 |
| 103 | 42 |
| 171 | 53 |
| 255 | |
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| 8 | 28 |
| 49 | 39 |
| 98 | 51 |
| 164 | 64 |
| 247 |
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| 0 | 0 |
| 88 | 0 |
| 175 | 0 |
| 295 | 0 |
| 447 |
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| 2 | 12 |
| 61 | 17 |
| 118 | 23 |
| 194 | 26 |
| 289 |
10 |
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5 | 23 |
| 57 | 32 |
| 113 | 41 |
| 187 | 52 |
| 280 | |
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| 10 | 30 |
| 51 | 41 |
| 104 | 54 |
| 176 | 67 |
| 267 |
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| 0 | 0 |
| 94 | 0 |
| 191 | 0 |
| 327 | 0 |
| 502 |
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| 2 | 11 |
| 69 | 15 |
| 136 | 20 |
| 226 | 22 |
| 339 |
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15 | 5 | 22 |
| 65 | 30 |
| 130 | 39 |
| 219 | 49 |
| 330 |
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| 10 | 29 |
| 59 | 40 |
| 121 | 51 |
| 206 | 64 |
| 315 |
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| 15 | 35 |
| 53 | 48 |
| 112 | 61 |
| 195 | 76 |
| 301 |
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| 0 | 0 |
| 97 | 0 |
| 202 | 0 |
| 349 | 0 |
| 540 |
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| 2 | 10 |
| 75 | 14 |
| 149 | 18 |
| 250 | 20 |
| 377 |
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| 5 | 21 |
| 71 | 29 |
| 143 | 38 |
| 242 | 47 |
| 367 |
20 |
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10 | 28 |
| 64 | 38 |
| 133 | 50 |
| 229 | 62 |
| 351 | |
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| 15 | 34 |
| 58 | 46 |
| 124 | 59 |
| 217 | 73 |
| 337 |
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| 20 | 48 |
| 52 | 55 |
| 116 | 69 |
| 206 | 84 |
| 322 |
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| 0 | 0 |
| 100 | 0 |
| 213 | 0 |
| 374 | 0 |
| 587 |
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| 2 | 9 |
| 81 | 13 |
| 166 | 14 |
| 283 | 18 |
| 432 |
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| 5 | 21 |
| 77 | 28 |
| 160 | 36 |
| 275 | 45 |
| 421 |
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30 | 10 | 27 |
| 70 | 37 |
| 150 | 48 |
| 262 | 59 |
| 405 |
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| 15 | 33 |
| 64 | 44 |
| 141 | 57 |
| 249 | 70 |
| 389 |
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| 20 | 56 |
| 58 | 53 |
| 132 | 66 |
| 237 | 80 |
| 374 |
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| 30 | NA |
| NA | 73 |
| 113 | 88 |
| 214 | 104 |
| 346 |
NOTE − Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45° elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi- mum listed capacity).
Page 18