440 01 4201 03
39
Specifications subject to change without notice.
Figure 47
Combustion Air and Vent Pipe Termination for Direct Vent (2
−
Pipe) System
L12F032
A
A
0
90
A
Vertical separation between
combustion air and vent
8
¾
in. (222mm) or 3 in.(76mm)
6
¾
in. (172mm) or 2in. (51mm)
Maintain 12 in. (305mm)
min. Clearance above
highest anticipated snow
level maximum of 24 in.
(614mm) above roof
18 in. Maximum
(457mm)
At least 36 in.
(914mm)
A
At least 36 in.
(914mm)
A
Concentric Vent and Combustion Air
Roof Termination (preferred)
Maintain 12 in. (305mm) min. Clearance
above highest anticipated snow level
maximum of 24 in. (614mm) above roof
1 in. (25mm) maximum
(Typ.) from wall to inlet
12 in. From Overhang
or roof (Typ.)
Abandoned masonry used
as raceway (per code)
Note:
“A” denotes 0 To 2 in. (51mm)
Between the first 2 vents Third
vent (and fourth vent, if used)
must be 36 in. Away (914mm)
12 in. Min from
overhang or
roof (Typ.)
At least 36 in.
(914mm)
12 in. (305mm) separation
between bottom of com
ï
bustion air and bottom of
vent (Typ.)
Maintain 12 in. (305mm) min.
Clearance above highest an
ï
ticipated snow level or grade
whichever is greater (Typ.)
At least 36 in.
(914mm)
At least 36 in.
(914mm)
Side wall termination of
less than 12 in. (305mm)
above highest snow level
Maintain 12 in. (305mm) min. Clear
ï
ance above highest anticipated snow
level or grade whichever is greater
(Typ.)
Concentric Vent and Combustion Air
Side Termination
Roof Termination (Preferred)
Note:
“A” denotes 0 To 2 in. (51mm)
Between the first 2 vents Third
vent (and fourth vent, if used) must
be 36 in. Away (914mm)
Note:
36
ï
in. separation between
pairs of inlets only required
for direct
ï
vent systems
Figure 48
Vent Pipe Termination for Ventilated Combustion Air System
Abandoned masonry
used as raceway
(per code)
12 in. (305 mm) min. from
overhang or roof
Maintain 12 in. (305mm)
minimum clearance
above highest anticipated
snow level or grade
whichever is greater.
Side wall termination
with 2 elbows (preferred)
12 in. min. (305 mm)from
overhang or roof
Maintain 12 in. (305mm)
minimum clearance
above highest anticipated
snow level or grade
whichever is greater
6 in. (152mm) minimum clearance
between wall and end of vent pipe.
10 in. (254mm) maximum pipe length
Sidewall Termination
with Straight Pipe (preferred)
Roof Termination (Preferred)
Vent
Maintain 12 in
.
minimum clearance
above highest anticipated
snow level maximum of
24 in. (610mm) above roof
.
90
°
(305mm)
A05091
Size the Vent and Combustion Air Pipes
General
Furnace combustion air and vent pipe connections are sized
for 2-in. (50 mm ND) PVC/ABS DWV pipe. The combustion air
and vent pipe connections also accommodate 60mm
polypropylene venting systems with outside diameters of
approximately 60 mm (2
−
3/8 inches). Any pipe diameter
change should be made outside furnace casing in vertical pipe.
Any change in diameter to the pipe must be made as close to
the furnace as reasonably possible.
The Maximum Vent Length for the vent pipe and combustion air
pipe equals the Maximum Equivalent Vent Length (MEVL) in
, minus the number of fittings multiplied by
the deduction for each type of fitting used from
