Single Stage Multi Position Furnace
Service Manual
14
440 08 2001 02
16. VENT/COMBUSTION AIR PIPING
Vent and combustion air piping are an extremely important
part of the total furnace installation. Improperly installed or
inadequately sized vent and/or combustion air piping can be
the source of many perceived furnace problems.
For example, most problems associated with pressure
switch operation can normally be traced to short comings in
the vent and/or combustion air piping. Anytime these type
problems arise, a thorough inspection of the vent and/or
combustion air piping should be conducted.
ALL MODELS
require a vent (exhaust) pipe to carry flue
products to the outside of the structure.
Direct VENT
(ONLY) models require a combustion air inlet
to bring in
all air for combustion from outside
the struc-
ture.
DUAL CERTIFIED
models require a combustion air inlet
pipe to bring in all air for combustion from outside the struc-
ture
only
when installed as a Direct Vent Furnace (I.E. Two
Pipe Installation)
Consult the appropriate Venting tables and/or piping chart
for the model (series) you are servicing.
17. STANDARD VENT TERMINATION
Vent/Combustion Air Piping Charts
Dual Certified Models ONLY - Non- Direct Vent
Installation
Single Piping Chart
Table 4
Pipe Diameter Table
Single Piping ONLY
50,000 & 75,000 Btuh Furnaces
40
¢
& (5) 90
°
elbows with 2
²
PVC pipe or
70
¢
& (5) 90
°
elbows with 3
²
PVC pipe or
100,000 Btuh Furnace
70
¢
& (5) 90
°
elbows with 3
²
PVC pipe
125,000 Btuh Furnace
40
¢
& (5) 90
°
elbows with 3
²
PVC pipe
Elbows are DWV Long Radius Type for 2
²
and
3
²
vents.
If more than five elbows are required, reduce the length of both
the inlet and exhaust pipes 5
¢
for each additional elbow used.
NOTE:
It is allowable to use larger diameter pipe and fitting than
shown in the tables but
not
smaller diameters than shown.
All Series (Models) - Direct Vent Installation
Dual Piping Chart
Table 5
Pipe Diameter Table
Dual Piping ONLY
50,000 & 75,000 Btuh Furnaces
40
¢
& (5) 90
°
elbows with 2
²
PVC pipe or
70
¢
& (5) 90
°
elbows with 3
²
PVC pipe or
100,000 Btuh Furnace
70
¢
& (5) 90
°
elbows with 3
²
PVC pipe
125,000 Btuh Furnace
40
¢
& (5) 90
°
elbows with 3
²
PVC pipe
Elbows are DWV Long Radius Type for 2
²
and
3
²
vents.
If more than five elbows are required, reduce the length of both
the inlet and exhaust pipes 5
¢
(1.5m) for each additional elbow
used.
*
Feet of pipe is whichever pipe run is the longest, either inlet
or
outlet side.
Figure 15
Standard Termination
Rooftop Termination
25--00--06
A
A
B
A = 12
²
Above roof or snow accumulation level
B = 8
²
Min., 20
¢
Maximum, except in areas with extreme cold
temperatures (sustained below 0
°
F), the 18
²
Min.
Inlet is optional on
Dual Certified models
Inlet is optional on
Dual Certified models
Figure 16
Sidewall Terminati
o
n 12
²
or More
Above Snow Level or Grade Level
8
²²²²
*
MIN.
20
’
MAX
*18
²
Minimum for cold climates
(substained below 0
°
F)
25--00--05F
