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Capacity of Type B Double Wall Vents with Single Wall Metal Connectors Serving a Single Category I Appliance
Height H
Lateral L
(feet)
(feet)
0
2
6
4
6
0
2
8
5
8
0
2
10
5
10
0
2
5
15
10
15
0
2
5
20
10
15
20
0
2
5
10
30
15
20
30
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).
507335-03
3 inch
Appliance Input Rating in Thousands of Btu per Hour
MIN
MAX
38
77
39
51
NR
NR
NR
NR
37
83
39
56
NR
NR
NR
NR
37
87
39
61
52
56
NR
NR
36
93
38
69
51
63
NR
NR
NR
NR
35
96
37
74
50
68
NR
NR
NR
NR
NR
NR
34
99
37
80
49
74
NR
NR
NR
NR
NR
NR
NR
NR
Vent and Connector Diameter - D (inches)
4 inch
MIN
MAX
59
151
60
96
74
92
83
89
58
164
59
108
77
102
90
95
57
174
59
117
76
111
97
100
56
190
57
136
75
128
95
116
NR
NR
54
200
56
148
73
140
93
129
NR
NR
NR
NR
53
211
55
164
72
157
91
144
115
131
NR
NR
NR
NR
Table 4.
Issue 2302
5 inch
MIN
MAX
85
249
85
156
102
152
114
147
83
273
83
176
107
168
122
161
82
293
82
193
105
185
132
171
80
325
80
225
102
216
128
201
158
186
78
346
78
248
100
239
125
223
155
208
186
192
76
372
76
281
98
271
122
255
151
239
181
223
NR
NR
6 inch
MIN
MAX
126
373
123
231
146
225
163
220
123
412
121
261
151
252
175
243
120
444
119
287
148
277
188
261
116
499
115
337
144
326
182
308
220
290
114
537
113
375
141
363
177
344
216
325
254
306
110
584
109
429
136
417
171
397
208
377
246
357
NR
NR
Page 19 of 39
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