
13
90°
Medium Radius
Elbow
12" Min.
Vent
24" Max.
3" Min.
Air Intake
12" Min.
Figure 8
Vertical Vent Termination
The vent and air intake pipe may be run through an
existing unused chimney. However, the pipes must be
run all the way through the chimney, with the air intake
pipe terminating at least 12 inches above the top of the
chimney.
See Figure 9 for explanation. The flue pipe must termi-
nate at least 12 inches above the air intake. The air
intake and exhaust may run side by side or as far apart
as necessary within the chimney.
The open space around the two pipes must be closed
with a weather tight, corrosion resistant flashing. NEVER
VENT WITH AN EXISTING APPLIANCE OR A VENT
USED BY A SOLID FUEL APPLIANCE.
Two 90° Medium
Radius Elbows
Air
Intake
Screen
12"
12"
Vent
Figure 9
Venting Through Existing Chimney
Vent/lntake Terminations For Installation
of Multiple Direct Vent Furnaces
If more than one direct vent furnace is to be installed
vertically through a common roof top, maintain the
same minimum clearances between the exhaust vent
and air intake terminations of adjacent units as with the
exhaust vent and air intake terminations of a single unit
(Figure 8).
If more than one direct vent furnace is to he installed
horizontally through a common side wall, maintain the
clearances as shown in Figure 10. Always terminate all
exhaust vent outlets at the same elevation and always
terminate all air intakes at the same elevation.
90°
Medium Radius
Elbows
12" Min.
Vents
24" Max.
3" Min.
Air Intakes
24" Max.
24" Max.
3" Min.
3" Min.
Figure 10
Horizontal Venting Of Multiple Units
Sizing Of Exhaust Vent And Combustion
Air Inlet Pipes
Consult Tables 1 to 4 to select the proper diameter
exhaust and combustion air piping. The vent and air
intake piping is sized for each unit model number based
on inside piping length and number of inside 90° elbows
required. Two 45° elbows are equivalent to one 90°
elbow. For all piping, the elbow(s) used for vent & air
pipe termination outside the structure as shown in Fig-
ures 6, 8, and 9 are not to be counted when using
Tables 1 through 4. The additional two 90° elbows as
shown in Figure 7 must be counted as part of the total
number of inside elbows when using Tables 1 - 4.
WHEN THE VENT SYSTEM REQUIRED IS BORDER-
LINE WITH NEXT SIZE COMBINATION CATEGORY,
USE THE NEXT LARGER SIZE.
IMPORTANT:
One short radius 90° elbow is equivalent
to 3-1/3 medium radius elbows. For this reason, short
radius 90° elbows must not be used. The proper
centerline-to-centerline dimensions for medium radius
90° elbows are shown below in Figure 11.
Elbow or
Coupling
Inside
Wall
90° Elbow
Outside
To Ground
12" Min.
3-1/16" Min. For 2" Pipe
4-9/16" Min. For 3" Pipe
Figure 11
Medium Radius Elbow Dimensions