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TABLE 6
Vent Connector Capacity
Type B Double-Wall Vents with Type B Double-Wall 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
22
37
35
66
46
106
58
164
2
23
41
37
75
48
121
60
183
3
24
44
38
81
49
132
62
199
8
1
22
40
35
72
49
114
64
176
2
23
44
36
80
51
128
66
195
3
24
47
37
87
53
139
67
210
10
1
22
43
34
78
49
123
65
189
2
23
47
36
86
51
136
67
206
3
24
50
37
92
52
146
69
220
15
1
21
50
33
89
47
142
64
220
2
22
53
35
96
49
153
66
235
3
24
55
36
102
51
163
68
248
20
1
21
54
33
99
46
157
62
246
2
2
57
34
105
48
167
64
259
3
23
60
35
110
50
176
66
271
30
1
20
62
31
113
45
181
60
288
2
21
64
33
118
47
190
62
299
3
22
66
34
123
48
198
64
309
TABLE 7
Common Vent Capacity
Type B Double-Wall Vents with Type B Double-Wall Connectors Serving Two or More Category I Appliances
Vent
Height
H
(feet)
Vent and Connector Diameter - D (inches)
4 inch
5 inch
7 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
92
81
140
116
204
161
309
248
8
101
90
155
129
224
178
339
275
10
110
97
169
141
243
194
367
299
15
125
112
195
164
283
228
427
352
20
136
123
215
183
314
255
475
394
30
152
138
244
210
361
297
547
459
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a
venting system commonly run with separate gas applianc-
es, the venting system is likely to be too large to properly
vent the remaining attached appliances.
Conduct the following test while each appliance is oper-
ating and the other appliances (which are not operating)
remain connected to the common venting system. If the
venting system has been installed improperly, you must
correct the system as indicated in the general venting re-
quirements section.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being placed
into operation could result in carbon monoxide poisoning
or death. The following steps shall be followed for each
appliance connected to the venting system being placed
into operation, while all other appliances connected to
the venting system are not in operation:
