A.O. Smith Residential Power Vent Gas Water Heaters with Hot Surface Ignition Instruction Manual page 18

Installing the New Water Heater (cont'd)
Venting (cont'd)
VENTING THROUGH AN OUTSIDE WALL (cont'd)
40 AND 50 GALLON 40,000 BTU/HR MODELS (3" VENT)
SEE CHART BELOW FOR MAX. LENGTH
4' MIN.
" MIN.
15 1 ⁄
2
14" MIN.
2. The total vertical and horizontal vent run cannot
exceed the maximum length with the number of 90°
elbows as specified in the tables below. If more elbows
are required the venting distance must be reduced 5
feet for every 90˚ elbow:
75 GALLON 70,000 and 75,000 BTU/HR, 50 GALLON
52,500, 55,000 and 62,500 BTU/HR and 40 GALLON
50,000 BTU/HR MODELS ONLY
3" " DIA. VENT
MAX. LENGTH (FT.)
70
65
60
55
50
45
75 GALLON 70,000 and 75,000 BTU/HR, 50 GALLON 52,500,
55,000 and 62,500 BTU/HR and 40 GALLON 50,000 BTU/HR
MODELS ONLY – OPTIONAL 4" VENT PIPING
4" " DIA. VENT
MAX. LENGTH (FT.)
110
105
100
95
90
85
ALL 40 and 50 GALLON 40,000 BTU/HR MODELS ONLY
3" " DIA. VENT
MAX. LENGTH (FT.)
115
110
105
100
95
90
"
MIN. RISE ⁄
1
8
PER FIVE FEET
NUMBER OF
90° ELBOWS*
1
2
3
4
5
6
NUMBER OF
90° ELBOWS*
1
2
3
4
5
6
NUMBER OF
90° ELBOWS*
1
2
3
4
5
6
ALL 40 and 50 GALLON 40,000 BTU/HR MODELS —
OPTIONAL 2" " VENT PIPING
2" " DIA. VENT
MAX. LENGTH (FT.)
50
45
40
35
30
25
*NOTE: Two 45° elbows are equivalent to one 90° elbow.
One 90° elbow equals 5 feet of equivalent vent length.
20'
(EXAMPLE)
3. Minimum vent length for all 40,000 BTU/HR input
models is 4 feet and 16 inches for all other models.
VENTING THROUGH AN OUTSIDE WALL WITH LOW
GROUND CLEARANCE
1. When the vent piping cannot pass through an outside
wall at a height greater than or equal to 12" above the
ground (or above snow accumulation level), then the
installation can be modified as shown below.
18
NUMBER OF
90° ELBOWS*
1
2
3
4
5
6
95' MAX.
"
MIN. RISE ⁄
1
8
PER FIVE FEET
ONE ELBOW
EXAMPLE
3" VENT PIPE
40 GALLON
40,000 BTU/HR
MODEL EXAMPLE
12" MIN. ABOVE
GROUND OR SNOW
ACCUMULATION LEVEL