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9
Installation of Standard Indoor
Venting
Standard Indoor Venting uses one penetration through
an exterior wall or roof for venting the flue exhaust.
The combustion air is supplied from the air inside the
building. Units must not be installed in a potentially
explosive, flammable, or corrosive atmosphere. To
prevent premature heat exchanger failure, do not
locate unit where chlorinated, halogenated or acid
vapors are present.
When units are installed in tightly sealed buildings,
provisions should be made to supply an adequate
amount of infiltration air from the outside. The rule of
thumb is that an opening of one square inch should be
provided for every 1000 BTUs per hour of input rating.
Vent terminals must be used. Construct the vent
system as shown in the drawings. Reference the Vent
Pipe Diameter table and Exhaust Vent Pipe table for
additional details.
Installing Exhaust Vent Pipe
Install the vent pipe with a minimum downward slope
(from the unit) of 1/4-inch per foot (horizontal venting
only). Securely suspend the pipe from overhead
structures at points no greater than 3 feet apart.
The minimum vent length is 5 feet for horizontal and
10feet for vertical. The maximum vent length is 70
feet. The total equivalent vent length must include
elbows. The equivalent length of a 4 inch elbow is 6
feet and the equivalent length of a 6 inch elbow is 10
feet. Attach the vent terminal to the end of the exhaust
pipe.
Vent Pipe Diameter
Select the vent pipe diameter. Use only the specified
pipe diameter.
Standard Indoor Venting - Vertical
Standard Indoor Venting - Horizontal
Vent
Length
Minimum
(feet)
Maximum
(feet)
Horizontal
5 70
Vertical
10 70
Furnace Size
(MBH)
Exhaust Pipe Diameter
(inches)
75 - 175
4
200 - 400
6
A = 12 inch minimum
Air Inlet
A
Exterior
Wall
Exhaust
Vent
Terminal
Pitch vent pipe
downward
from furnace
¼ inch per foot
EXHAUST
A A
Exhaust Vent
Terminal
EXHAUST
A = 12 inch minimum
B = 12 inch minimum,
but should size
according to expected
snow depth
Air Inlet
B
Roof Line
®
Model IG / IGX Make-Up Air