LAARS U.H.E. - Installation Manual - Manual (Page 28)

Figure 18. Vent Terminal (Low Ground Clearance)
Maximum Vent Length Determination
Power Vent Maximum Vent Length
Storage
Capacity
(Gallons)
Rated Input
(BTU/HR)
Max Vent Length (feet)
3" PVC, CPVC, or ABS
Max Vent Length (feet)
4" PVC, CPVC, or ABS
60 125,000 120 170
60 150,000 100 150
60
100
100
100
100
100
199,999
150,000
199,999
250,000
300,000
399,999 80
120
100
80
60
50
130
170
150
130
110
100
Table 4
Determining required vent length:
1. Determine the total length of straight vent pipe (in feet) required.
2. Add 5 feet of venting for every 90° elbow.
3. Add 2 ½ feet of venting for every 45° elbow.
4. Total vent length cannot exceed “Max. Vent Length” in Table 4.
Example of Total Vent Length for 100 gallon 199,999 btuh model with a power vented
installation:
A 3” venting system has a total of six 90-degree elbows and a total straight pipe length of 55 feet.
Equivalent vent length for elbows: 6 x 5 feet = 30 feet.
Total equivalent vent distance = 55 feet + 30 feet = 85 feet total equivalent vent length. This is
below the maximum allowed distance of 100 feet for this model using 3” vent.
NOTICE
Do not include the 3” condensate elbow or vent terminals in determining maximum vent
length.
28