13
58MCB
ALTITUDE (FT)
UNIT SIZE
(BTUH)
DIRECT VENT (2-PIPE) ONLY
NON-DIRECT VENT
(1-PIPE) ONLY
NUMBER OF 90° ELBOWS
TERMINATION
TYPE
PIPE DIA
(IN.)*
PIPE DIA
(IN.)*
12 3 4 5 6
4001 to 5000‡
40,000
2 Pipe or 2-in
Concentric
1-1/2 1-1/2 60 55 50 45 44 39
2 2 70 70 70 70 70 70
60,000
2Pipeor2-in
Concentric
1-1/2 1-1/2 15 10 5 NA NA NA
2 2 64 59 58 53 52 52
80,000
2Pipeor2-in
Concentric
2 2 44 39 26 21 20 11
2-1/2 2-1/2 70 70 70 70 70 70
100,000
2Pipeor3-in
Concentric
2-1/2 2-1/2 31 22 13 12 NA NA
3 3 70 70 67 62 57 52
120,000
2 Pipe or 3-in.
Concentric
3† no disk NA 53 46 40 33 26 20
NA 3† 56 55 54 53 52 52
4† no disk 4† no disk 70 70 70 70 70 70
140,000
2 Pipe or 3-in.
Concentric
3† no disk NA 21 17 13 9 5 NA
4† no disk NA 69 64 59 54 49 44
ALTITUDE (FT)
UNIT SIZE
(BTUH)
DIRECT VENT (2-PIPE) ONLY
NON-DIRECT VENT
(1-PIPE) ONLY
NUMBER OF 90° ELBOWS
TERMINATION
TYPE
PIPE DIA
(IN.)*
PIPE DIA
(IN.)*
12 3 4 5 6
5001 to 6000‡
40,000
2Pipeor2-in
Concentric
1-1/2 1-1/2 57 52 47 42 40 35
2 2 70 70 70 70 70 70
60,000
2Pipeor2-in
Concentric
1-1/2 1-1/2 14 9 NA NA NA NA
2 2 60 55 54 49 48 47
80,000
2 Pipe or 2-in
Concentric
2 2 41 36 23 18 17 8
2-1/2 2-1/2 70 70 70 70 70 70
100,000
2 Pipe or 3-in
Concentric
2-1/2 2-1/2 29 21 12 11 NA NA
3 3 70 67 62 57 52 47
120,000
2 Pipe or 3-in.
Concentric
3† no disk NA 42 35 29 22 15 9
NA 3† 53 52 50 49 48 47
4† no disk 4† no disk 70 70 70 70 70 70
140,000
2 Pipe or 3-in.
Concentric
3† no disk NA 12 8 NA NA NA NA
4† no disk NA 42 37 32 27 22 17
ALTITUDE (FT)
UNIT SIZE
(BTUH)
DIRECT VENT (2-PIPE) ONLY
NON-DIRECT VENT
(1-PIPE) ONLY
NUMBER OF 90° ELBOWS
TERMINATION
TYPE
PIPE DIA
(IN)*
PIPE DIA
(IN)*
12 3 4 5 6
6001 to 7000‡
40,000
2 Pipe or 2-in
Concentric
1-1/2 1-1/2 53 48 43 38 37 32
2 2 70 70 68 67 66 64
60,000
2Pipeor2-in
Concentric
1-1/2 1-1/2 13 8 NA NA NA NA
2 2 57 52 50 45 44 43
80,000
2Pipeor2-in
Concentric
2 2 38 33 21 16 15 6
2-1/2 2-1/2 70 70 68 67 66 64
100,000
2Pipeor3-in
Concentric
2-1/2 2-1/2 27 19 10 9 NA NA
3 3 68 63 58 53 48 43
120,000
2 Pipe or 3-in.
Concentric
3† no disk NA 31 24 18 11 NA NA
NA 3† 49 48 47 45 44 43
4† no disk 4† no disk 70 70 70 70 67 62
140,000
2 Pipe or 3-in.
Concentric
4† no disk NA 17 12 7 NA NA NA
See notes at end of table
Combustion-air and vent piping for Direct Vent/2-Pipe 
(All Sizes) and Non-Direct Vent/1-Pipe (Sizes 040 
through 120 Only) Applications