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Type B Double Wall Vents with Single Wall Metal Connectors Serving Two or More Category I Appliances
Vent
Lateral L
Height H
(feet)
(feet)
1
6
2
3
1
8
2
3
1
10
2
3
1
15
2
3
1
20
2
3
1
30
2
3
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 maximum listed capacity).
Type B Double Wall Vents with Single Wall Metal Connectors Serving Two or More Category I Appliances
Vent Height
H (feet)
FAN + FAN
6
NA
8
NA
10
NA
15
121
20
131
30
145
507335-03
Vent Connector Capacity
3 inch
Appliance Input Rating in Thousands of Btu per Hour
MIN
MAX
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
49
56
52
59
55
62
47
60
51
62
54
64
4 inch
Appliance Input Rating in Thousands of Btu per Hour
FAN + NAT
FAN + FAN
78
NA
87
NA
94
163
108
189
118
208
132
236
Vent and Connector Diameter - D (inches)
4 inch
MIN
MAX
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
84
85
89
91
79
87
83
94
87
100
78
97
82
103
87
107
77
110
81
115
85
119
Table 7.
Common Vent Capacity
Common Vent Diameter
5 inch
FAN + NAT
FAN + FAN
113
126
137
159
177
202
Table 8.
Issue 2302
5 inch
MIN
MAX
NR
NR
NR
NR
121
131
NR
NR
125
126
130
138
119
121
124
134
129
144
116
138
121
150
127
160
115
152
120
163
125
172
112
175
117
185
122
193
6 inch
FAN + NAT
FAN + FAN
200
158
218
173
237
189
275
221
305
247
350
286
6 inch
MIN
MAX
NR
NR
168
182
175
198
NR
NR
184
193
191
208
182
186
189
203
197
217
177
214
185
230
193
243
175
238
182
252
190
264
169
278
177
290
185
300
7 inch
FAN + NAT
304
244
331
269
357
292
416
343
463
383
533
446
Page 21 of 39
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