TECHNICAL DATA VENTING
®
NOTES FOR MULTIPLE APPLIANCE VENTING
(SEE TABLES 13.1, 14.1 AND 14.2)
1. Maximum Vent Connector Length 1-1/2 feet for every inch of connector diameter. Greater lengths require increase in size, rise
or total vent height, to obtain full capacity.
2. Each 90-degree turn in excess of the first two reduces the connector capacity by 10 percent.
3. Each 90-degree turn in the common vent reduces capacity by 10
percent.
4. Where possible, locate vent closer to or directly over smaller
appliance connector.
5. Connectors must be equal to or larger than draft hood outlets.
6. If both connectors are same size, common vent must be at least
one size larger, regardless of tabulated capacity.
7. Common vent must be equal to or larger than largest connector.
8. Interconnection fittings must be same size as common vent.
9. Use sea level input rating when calculating vent size for high
altitude installation.
10. Designation “NR” in Tables 13.1, 14.1 & 14.2 indicates not recommended.
CAPACITY OF TYPE B DOUBLE-WALL VENT
13.1
Total Connector
Vent
Rise
Height
“R”
“H”
1'
6'
2'
3'
1'
8'
2'
3'
1'
10'
2'
3'
1'
15'
2'
3'
1'
20'
2'
3'
1'
30'
2'
3'
1'
40'
2'
3'
60’ to
1'
100'
2'
3'
4"
5"
26
31
35
27
32
36
28
33
37
30
35
40
31
37
42
33
39
44
35
41
46
37
44
50
46
55
62
48
57
64
50
59
67
53
63
71
56
66
74
59
70
79
62
73
83
66
79
89
72
86
96
76
90
101
78
93
104
83
99
111
87
104
116
93
110
124
97
115
129
104
123
138
Total Vent
Height
"H"
3"
Common Vent Diameter
4"
5"
6"
7"
8"
10"
12"
14"
16"
Combined Appliance Input Rating in Thousands of Btu Per Hour
6'
8'
10'
15'
20'
30'
40'
60'
80'
100'
–
–
–
–
–
–
–
–
–
–
65
73
79
91
102
118
131
NR
NR
NR
103
114
124
144
160
185
203
224
NR
NR
6"
7"
Vent Connector Diameter-D
8"
10"
12"
14"
3"
16"
18”
20"
22"
24"
1180
1335
1510
1255
1420
1610
1310
1490
1690
1420
1610
1835
1510
1710
1945
1645
1855
2110
1735
1965
2240
1890
2150
2450
1425
1610
1830
1520
1720
1950
1585
1800
2040
1720
1950
2220
1830
2070
2350
1990
2240
2550
2100
2380
2710
2280
2590
2960
1700
1920
2180
1810
2050
2320
1890
2150
2430
2050
2320
2640
2190
2470
2800
2370
2670
3040
2500
2830
3230
2720
3090
3520
18"
20"
22"
24"
1345
1510
1645
1910
2140
2520
2830
3320
3710
4050
1660
1860
2030
2360
2640
3110
3500
4100
4590
5000
1970
2200
2400
2790
3120
3680
4150
4850
5420
5920
2390
2680
2920
3400
3800
4480
5050
5900
6600
7200
Maximum Appliance Input Rating in Thousands of Btu Per Hour
104
142
185
289
416
577
755
955
124
168
220
345
496
653
853 1080
139
189
248
386
556
740
967 1225
109
148
194
303
439
601
805 1015
129
175
230
358
516
696
910 1150
145
198
258
402
580
790 1030 1305
113
154
200
314
452
642
840 1060
134
182
238
372
536
730
955 1205
150
205
268
417
600
827 1080 1370
120
163
214
333
480
697
910 1150
142
193
253
394
568
790 1030 1305
160
218
286
444
640
898 1175 1485
125
171
224
347
500
740
965 1225
149
202
265
414
596
840 1095 1385
168
228
300
466
672
952 1245 1575
134
182
238
372
536
805 1050 1330
158
215
282
439
632
910 1190 1500
178
242
317
494
712 1035 1350 1710
140
190
248
389
560
850
1110 1405
166
225
295
461
665
964 1260 1590
187
253
331
520
748 1100 1435 1820
150
204
266
417
600
926 1210 1530
178
242
316
494
712 1050 1370 1740
200
272
355
555
800 1198 1565 1980
147
163
178
206
229
266
295
324
344
NR
200
223
242
280
310
360
405
440
468
479
260
290
315
365
405
470
525
575
610
625
410
465
495
565
640
740
820
900
955
975
588
652
712
825
916
1025
1180
1380
1540
1670
815
912
995
1158
1290
1525
1715
2010
2250
2450
1065
1190
1300
1510
1690
1990
2240
2620
2930
3200
See Figure 3 and Notes for Multiple Appliance Vents.
April
2011R
(Reviewed
March 1996)
AOSTD63110
C 013.0
TECHNICAL DATA VENTING
CAPACITY OF A SINGLE-WALL METAL PIPE
OR TYPE B ASBESTOS CEMENT VENT
14.1
14.2
Vent Connector Capacity
Vent Connector Diameter-D
Total Vent
Height
“H”
Connector
Rise
“R”
3"
1'
2'
3'
1'
2'
3'
1'
2'
3'
21
28
34
23
30
35
25
31
36
6'-8'
15'
30'
and up
4"
5"
6"
7"
8"
Maximum Appliance Input Rating in
Thousands of Btu Per Hour
40
53
61
44
56
64
49
58
68
68
86
98
77
92
102
84
97
107
102
124
147
117
134
155
129
145
164
146
178
204
179
194
216
190
211
232
205
235
275
240
265
298
270
295
321
Common Vent Diameter
4"
6'
8'
10'
15'
20'
30'
50'
48
55
59
71
80
NR
NR
5"
6"
7"
8"
10"
12"
Combined Appliance Input Rating In
Thousands of Btu Per Hour
78
89
95
115
129
147
NR
111
128
136
168
186
215
NR
155
175
190
228
260
300
360
205
234
250
305
340
400
490
Total Vent
Rise
Height Connector
“H”
“R”
1'
2'
3'
1'
2'
3'
1'
2'
3'
6'-8'
15'
30'
and up
320
365
395
480
550
650
810
NR
505
560
690
790
940
1190
3"
Vent Connector Diameter-D
4"
5"
6"
7"
Maximum Appliance Input Rating In
Thousands of Btu Per Hour
21
28
34
23
30
34
24
31
35
39
52
61
43
54
63
47
57
65
66
84
97
73
88
101
80
93
105
100
123
142
112
132
151
124
142
160
140
172
202
171
189
213
183
205
229
8"
200
231
269
225
256
289
250
282
312
Common Chimney Capacity
Total Vent
Height
“H”
Common Vent Capacity
Total Vent
Height
“H”
CAPACITY OF A MASONRY CHIMNEY
AND SINGLE-WALL VENT CONNECTORS
Single-Wall Vent Connector Capacity
6'
8'
10'
15'
20'
30'
50'
Minimum Internal Area of Chimney-”A”
Square Inches
19
28
38
50
78
113
Combined Appliance Input Rating in
Thousands of Btu Per Hour
45
52
56
66
74
NR
NR
71
81
89
105
120
135
NR
102
118
129
150
170
195
NR
142
162
175
210
240
275
325
245
277
300
360
415
490
600
NR
405
450
540
640
740
910
See Table 12.3 Page C
AOSTD63100
for Masonry
Chimney
Liner Sizes.
012.0 for Masonry
Chimney
Liner Sizes.
See Figure
FIgure 4 and
and Notes
Notes for
for Multiple
Multiple Appliance
ApplicanceVents.
Vents.
See Figure 3 and Notes for Multiple Appliance Vents.
1. WATER HEATER VENT CONNECTOR SIZE
EXAMPLE OF MULTIPLE VENT DESIGN
Using Table 12-1 read down Total Vent Height “H” column to 15 feet
and read across 1 foot connector rise “R” line to Btu rating equal to or
higher than water heater input rating. This figure shows 53,000 Btu
and is in the column for four-inch connector. Since this is in excess of
the water heater input it is not necessary to find the maximum input for
an 18 foot minimum total vent height. Use a four-inch connector.
2. FURNACE VENT CONNECTOR SIZE
Under Vent Connector Tables read down Total Vent Height “H" column to 15 foot and read across 2 foot Connector Rise “R” line. Note 5
inch vent size shows 99,000 Btu per hour or less than furnace input.
However, with 20 foot Total Height read across 2 foot connector rise
line. Note 5 inch vent size shows 104,000 Btu per hour. Since 18 foot
height is 3/5th of difference between 15 and 20 foot heights take difference between 99,000 and 104,000 or 5,000 and add 3/5ths of this to
15 foot figure of 99,000, 99,000 + 3,000 = 102,000 which is maximum
input for 18 foot Total Vent Height. Therefore a 5-inch connector would
be the correct size for the furnace, providing the furnace had a five-inch
or smaller draft hood outlet.
3. COMMON VENT SIZE
Total input to Common Vent is 145,000 Btu. Note that for 15 foot
Total Vent Height “H” maximum Btu for 5 inch vent is 144,000. For 20
foot Total Vent Height “H” maximum Btu for 5 inch vent is 160,000.
Therefore for 18 foot Total Vent Height maximum allowable input
would be 3/5th of difference between 144,000 and 160,000 = 3/5 X
16,000 or 9,600. 144,000 + 9,600 = 153,600 which is greater than total
input to common vent. Therefore common vent can be 5 inch diameter
pipe.
AOSTD63110
C 014.0
© A. O. Smith Corp., 1983
2011
Printed in U.S.A.