11
Air Directly Through An Exterior Wall
If combustion air is provided directly through an
exterior wall, the two openings must
each have
free area of at least one square inch per 4000
Btuh of
total appliance input. (See Figure 6.)
Outdoor Air Through Vertical Openings or Ducts
If combustion air is provided through vertical
ducts or openings to attics or crawl spaces, the
two openings must each have free area of at
least one square inch per 4000 Btuh of total
appliance input. Ducts must have cross-sec-
tional areas at least as large as the free area of
their respective openings to the furnace space.
Attics or crawl spaces must communicate freely
with the outdoors if they are the source of air for
combustion and ventilation. (See Figures 7 and
8.)
Outdoor Air Through Horizontal
Openings or Ducts
If combustion air is taken from outdoors through
horizontal ducts, the openings must
each have
free area of at least one square inch per 2000
Btuh of total appliance input. Ducts must have
cross-sectional area at least as large as the free
area of their respective openings to the furnace
space. (See Figure 9.)
**NOTES
1.
Subtract 2.5 ft. for each additional 2"
long
radius elbow, 5 ft. for each additional 2"
short
radius elbow, 3.5’ for each
additional 3”
long
radius elbow, and 7’ for each additional 3”
short
radius elbow.
2.
Two 45 degree elbows are equivalent to one 90 degree elbow.
3.
Do not include termination elbows in calculation of vent length
4.
This table is applicable for elevations from sea level to 2000 ft. For higher elevations decrease vent pipe lengths
by 8% per 1000 ft. of altitude.
5.
Only the above pipe materials are approved for use with these condensing furnaces.
Table 3. Vent Table
APPLICATION
SINGLE PIPE LENGTH (ft.)
DIRECT VENT, DUAL PIPE LENGTH (ft.)
with 1 long radius elbow**
with 1 long radius elbow on each pipe**
PVC,CPVC or ABS
Outlet
Outlet
Inlet/Outlet
Inlet/Outlet
Inlet/Outlet
SCH. 40 Pipe Size
2"
3"
2"
2"
3"
2"
3"
3"
Models
*TE
65
200
30
30
40
40
110
110
060
Models
*TE
45
200
30
30
40
40
110
110
80
Models
*TE
40
200
25
25
40
40
110
110
100
Models
*TE
40
200
20
20
40
40
110
110
120
!
CAUTION:
Do not supply combustion air from an
attic space that is equipped with power
ventilation or any other device that
may produce a negative pressure.
VENTING REQUIREMENTS
This section specifies installation requirements
for vent and "2-pipe" combustion air piping. For
"one pipe" installations, install vent piping per
this section and provide air for combustion and
ventilation per the previous section. The ca-
pacity table provided in this section applies to
the total of vent and combustion air piping for
either type of installation.
These condensing furnaces are classified as
"Category IV" appliances, which require spe-
cial venting materials and installation proce-
dures. Category IV appliances operate with
positive vent pressure and therefore require
vent systems which are thoroughly sealed.
They also produce combustion condensate,
