Downflow Furnace
Vent
Combust on _ _ p ,
Air intake Pipe _... I "" .i I
Seal/Caulk See Vent Table 4 _ _,-_ ._.
Around Pipe -- !_ "1_ i (1_
at Building \\ ', Straps or Other Suitable / _ I
\\ I Supports at Minimum of I
\"\ _ 5 ft" Inltervals I_ _
\
90 ° E bow \ '<, _ Coupling // / _\\ \, Top View
\ _ _ i' r-i i-i ii r-i
........ j
_2_,_ [_J,l_ _ 4, Wal Upward Pitch = 1/4" Per F°°t A
MIn i _ Wail Outlet Exhaust Vent
First Support Should be as Close to
Furnace Connection as Possible
Combustion Air
intake Pipe Furnace
Normal Snow Level
_!3 9/t 6",_
1 7/8"
Offset with
Vent for Adequate
Dimensional Clearance
Exhaust
Vent
PVC or
ABS pipe
3"x 2"
Reducer
Figure 16. Horizontal Venting
Combustion Air !_
Intake Pipe
®
Support System
on Vertical Rise
Below Joints
...Vent
First support should be as
close to furnace as possible
" Combustion Air intake Pipe
-ooVent
Upward Pitch
1/4" per foot
J-..
Figure 17. Vertical Venting
per the piping manufacturer's recommendation
and ASTM Standard D3138.
Vent Pipe Installation
Pipe Routing and Support
Route piping as directly as possible between
the furnace and the outdoors and remember
that routing affects pipe length limitations per
Table 6. Locate the combustion air intake and
the vent exhaust in the same atmospheric
pressure zone - i.e. both must exit the building
though the same portion of exterior wall or roof.
Vent piping must be sloped upwards not less
than 1/4" per foot in the direction from the
furnace to the terminal. This is to ensure that
any condensate flows back to the furnace
where it can be disposed of through the
condensate disposal system.
CAUTION:
Combustion air must not be drawn from
occupied spaces and a corrosive
atmosphere,
The quality of outdoor air must also be
considered. Be sure that the combustion air
intake is not located near a source of solvent
17
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