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Special Case Venting
Special instructions for direct vent furnace air intake.
In certain applications, particularly when the furnace is located in a
basement, there are certain conditions that can be met where warm
humid air from the outside is drawn into combustion air piping. If the
area where the piping is located is conditioned below 70° F,
condensation could occur inside the piping and ultimately drain into
the furnace compartment, which could lead to premature component
failure.
We recommend following one of the options to prevent this condition
from occurring and possibly damaging components within the
furnace:
Option 1
If possible, slope the inlet combustion air piping away from the
furnace. Condensation that may occur will now drain outside of the
home. The combustion air exhaust must be sloped back to the
furnace.
Note: Combustion air drain fitting must remain capped if not using
the drain function. See
section.
Option 1
Combustion air
exhaust
Combustion air
intake
Slope equals 1/4" per foot
Primary drain vent stack must
terminate below the bottom of
the condensate trap
To an approved
vented drain
Option 2– Top combustion air intake
If sloping the combustion air intake pipe is not possible, install a DWV
Tee as close to the furnace as possible with drain and trap to prevent
condensation from occurring in the furnace cabinet. Do not tee AC
condensate and combustion air condensate trap together.
Note: Combustion air drain fitting must remain capped if not using
the drain function. See
section.
Option 2
Slope equals 1/4" per foot
Combustion air
exhaust
Combustion air
intake
Approved DWV Tee
Field fabricated trap
Primary drain vent stack must
terminate below the bottom of
the condensate trap
To an approved
vented drain
S9V2-VS-SVX001-1C-EN
"Condensate Drain Instructions," p. 60
"Condensate Drain Instructions," p. 60
F F u u r r n n a a c c e e G G e e n n e e r r a a l l I I n n s s t t a a l l l l a a t t i i o o n n
Note: Inlet air piping is not considered to be part of the venting
system. The inlet air piping may be made from PVC.
Option 3 – Side combustion air intake
If sloping the combustion air intake pipe is not possible, install an
approved DWV Tee as close to the furnace as possible with drain and
trap.
Note: Combustion air drain fitting must remain capped if not using
the drain function. See
"Condensate Drain Instructions," p. 60
section.
Option 3
Combustion air
intake
Approved DWV Tee
Field fabricated trap
Primary drain vent stack must
terminate below the bottom of
the condensate trap
To an approved
vented drain
Combustion air
exhaust
33
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