Troubleshooting guide

15
34-52 07/13
8.3 Maximum Category IV Vent Length (Equivalent Length)
A vertical or horizontal remote Category IV vent system must be used with this appliance. The maximum length of
field supplied Category IV vent is shown in the chart below titled Category IV Vent Equivalent Length.
Maximum Category IV Vent Equivalent Length
Vent Size 6” Vent 7” Vent 8” Vent 9” Vent
Max Equivalent Length
100 feet 130 feet 250 feet 450 feet
Pipe fittings reduce the maximum allowable vent length. Use the Category IV vent manufacturer’s equivalent length
deduction for all elbows, terminations, etc. If the information is not readily available from the vent manufacturer, use
the Vent Fitting Equivalent Length chart below to find the total equivalent length for all vent fittings in your
combustion air system. Then subtract this number of feet from the total equivalent length allowed in Maximum
Category IV Vent Equivalent Length chart above. The sum of this calculation is the maximum length of straight vent
allowed. If a longer length is required, repeat the calculation using a larger vent size. When using this chart, no
additional deduction is required for the addition of the vent system terminal.
The following vent information is provided for use in design calculations, if needed.
Venting Specifications
Boiler
Input Mbtu
Required
Air (cfm)
Max Vent
Press. "W.C.
1500 350 1.7
1800 420 2.0
2000 467 2.0
8.4 Vertical or Horizontal Vent Termination
The vent terminal must extend at least 3 ft (.09 m) above the highest point where it passes through the roof of a
building and at least 2 ft. (.06 m) higher than any portion of a building within a horizontal distance of 10 ft. (3.0 m).
The vent cap must terminate at least 3 feet (0.91 m) above any forced air inlet within 10 feet (3.05 m); 4 feet (1.22 m)
below, 4 feet (1.22 m) horizontally from or 1 foot (0.3 m) above any door, window or gravity air inlet to the building; 1
foot (0.3 m) above grade; 1 foot (0.3m) above normal snow levels and shall terminate at least 7 feet (2.13 m) above
grade when located adjacent to public walkways or gathering areas.
The vent terminal should not be installed closer than 3 feet (0.91 m) from an inside corner of an L-shaped structure.
Vent Fitting Equivalent Length
Vent Pipe: 6” Vent 7” Vent 8” Vent 9” Vent
90º Elbow 8 feet 9 feet 10 feet 11 feet
90º Long Radius Elbow 5 feet 5 feet 5 feet 6 feet
45º Elbow 5 feet 5 feet 5 feet 5 feet