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TABLE 7
Vent Connector Capacity
Type B Double−Wall Vents with Single−Wall Metal Connectors
Serving Two or More Category I Appliances
Height
H
(feet)
Lateral
L
(feet)
Vent and Connector Diameter − D (inches)
3 Inch 4 Inch 5 Inch 6 Inch
Appliance Input Rating in Thousands of Btu Per Hour
MIN MAX MIN MAX MIN MAX MIN MAX
6
1 NA NA NA NA NA NA NA NA
2
NA NA NA NA NA NA
168 182
3 NA NA NA NA 121 131 175 198
8
1 NA NA NA NA NA NA NA NA
2 NA NA NA NA 125 126 184 193
3 NA NA NA NA 130 138 191 208
10
1 NA NA NA NA 119 121 182 186
2 NA NA 84 85 124 134 189 203
3 NA NA 89 91 129 144 197 217
15
1 NA NA 79 87 116 138 177 214
2 NA NA 83 94 121 150 185 230
3 NA NA 87 100 127 160 193 243
20
1 49 56 78 97 115 152 175 238
2 52 59 82 103 120 163 182 252
3 55 62 87 107 125 172 190 264
30
1 47 60 77 110 112 175 169 278
2 51 62 81 115 117 185 177 290
3 54 64 85 119 122 193 185 300
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).
TABLE 8
Common Vent Capacity
Type B Double−Wall Vents with Single−Wall Metal Connectors
Serving Two or More Category I Appliances
Vent
Height
H
(feet)
Common Vent Diameter − D (inches)
4 Inch 5 Inch 6 Inch 7 Inch
Appliance Input Rating in Thousands of Btu Per Hour
FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT
6 NA 78 NA 113 200 158 304 244
8 NA 87 NA 126 218 173 331 269
10 NA 94 163 137 237 189 357 292
15 121 108 189 159 275 221 416 343
20 131 118 208 177 305 247 463 383
30 145 132 236 202 350 286 533 446