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TABLE 9
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 10
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