7. Allexhaustventpipingfromthefurnacetotermination
MUST slope upwards. A minimum of 1/4" per foot of run is
required to properly return condensate to the furnace drain
system.
8. Use DWV type long radius elbows whenever possible, as
they provide for the minimum slope on horizontal runs and
they provide less resistance in the vent system. If DWV el-
bows cannot be used, use two, 45 ° elbows when possible.
On horizontal runs the elbows can be slightly misaligned to
provide the correct slope.
All horizontal pipe runs MUST be supported at least every
five feet with galvanized strap or other rust resistant materi-
al. NO sags or dips are permitted.
10. All vertical pipe runs MUST be supported every six feet
where accessible.
11. The maximum pipe length is 40' total in the inlet or outlet
side of the system. Up to five, 90 ° elbows can be used on
the inlet or the outlet. With the Concentric Vent Termination
Kits (NAHA001CV or NAHA002CV), the maximum pipe
length is 35' with 4 90 ° elbows. If more elbows are required,
reduce the length of both the inlet and exhaust pipes 5' for
each additional elbow used. (See Table 3 or Table 4).
12. The minimum pipe run length is 2'.
13. The piping can be run in the same chase or adjacent to sup-
ply or vent pipe for water supply or waste plumbing. It can
also be run in the same chase with a vent from another 90+
furnace.
NOTE: In NO case can the piping be run in a chase where
temperatures can exceed 140 ° E or where radiated heat
from adjacent surfaces would exceed 140 ° F.
14. The vent outlet MUST be installed to terminate in the same
atmospheric pressure zone as the combustion air inlet.
15. The vent system can be installed in an existing unused
chimney provided that:
• Both the exhaust vent and air intake run the length ofthe
chimney.
• No other gas fired appliance or fireplace (solid fuel) is
vented into the chimney.
• The top of the chimney MUST be sealed flush or
crowned up to seal against rain or melting snow so ONLY
the piping protrudes.
• The termination clearances shown in Figure 7 are main-
tained.
16.
Furnace applications with vertical vents requiring vent di-
ameter increaser fittings must have increaser fittings
installed in vertical portion of the vent. Condensate will be
trapped in the vent if the vent diameter is increased prior to
having an elbow turned upward. This could cause nui-
sance tripping of the pressure switch.
PipingInsulation Guidelines
NOTE: Use closed cell, neoprene insulation or equivalent. If Fi-
berglass or equivalent insulation is used it must have a vapor bar-
rier. Use R values of 7 up to 10', R- 11 if exposure exceeds 10'. If
Fiberglass insulation is used, exterior to the structure, the pipe
MUST be boxed in and sealed against moisture.
.When the vent or combustion air pipe height above the
roof exceeds 30", or if an exterior vertical riser is used on a
horizontal vent to get above snow levels, the exterior por-
tion MUST be insulated.
2. When combustion air inlet piping is installed above a sus-
pended ceiling, the pipe MUST be insulated with moisture
resistant insulation such as Armaflex or other equivalent
type of insulation.
3. Insulate combustion air inlet piping when run in warm, hu-
mid spaces such as basements.
Sizing Combustion Air and VentPipe
Consult Table 3 or Table 4 to select the proper diameter exhaust
and combustion air piping. Exhaust and combustion air piping is
sized for each furnace Btuh size based on total lineal vent length
(on inlet or outlet side), and number of 90 ° elbows required.
1. Double Pipe Installation-If installing as a direct-vent ap-
pliance, consult Table 4 to select the proper diameter ex-
haust and combustion air piping. Exhaust and combustion
air piping is sized for each furnace Btuh size based on total
lineal vent length (on inlet or outlet side), and number of 90 °
elbows required.
2. Single Pipe Installation-if installing as a non-direct vent
appliance, (single outlet pipe and no inlet pipe) refer to
Table 3. The table shows the maximum number of elbows
allowed with any given pipe diameter and length of run.
3. Use of Elbows-Two 45 ° elbows can be substituted for one
90 ° elbow. The elbow or elbows used for vent termination
outside the structure ARE counted, including elbows need-
ed to bring termination above expected snow levels.
Pipe Diameter Table
Single Piping ONLY
50,000 & 75,000 Btuh Furnaces
40' & (5) 90° elbows with 2" PVC pipe or
100,000 Btuh Furnace
40' & (5) 90 ° elbows with 3" PVC pipe
125,000 Btuh Furnace
40' & (5) 90 ° elbows with 3" PVO pipe
Elbows are DWV Long Radius Type for 2" and 3" 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.
Pipe Diameter Table
Dual Piping ONLY
50,000 & 75,000 Btuh Furnaces
40' & (5) 90° elbows with 2" PVC pipe or
100,000 Btuh Furnace
40' & (5) 90 ° elbows with 3" PVC pipe
125,000 Btuh Furnace
40' & (5) 90 ° elbows with 3" PVO pipe
Elbows are DWV Long Radius Type for 2" and 3" vents.
If more than five elbows are required, reduce the length of
both the inlet and exhaust pipes 5' for each additional elbow
used.
* Feet of pipe is whichever pipe run is the longest, either inlet
or outlet side.
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