506550-01Page 14 of 66 Issue 1230
Venting Practices 1. In areas where piping penetrates joist or interior walls,
hole must be large enough to allow clearance on all sides
of pipe through center of hole using a hanger.
2. When furnace is installed in a residence where unit is
shut down for an extended period of time, such as a
vacation home, make provisions for draining condensate
collection from trap and lines.
Exhaust Piping (Figures 18 and 19)
3. Route piping to outside of structure. Continue with
installation following instructions given in piping
termination section.
The exhaust vent pipe operates under positive pressure
and must be completely sealed to prevent leakage of
combustion products into the living space.
CAUTION
Do not discharge exhaust into an existing stack or stack
that also serves another gas appliance. If vertical
discharge through an existing unused stack is required,
insert PVC pipe inside the stack until the end is even
with the top or outlet end of the metal stack.
CAUTION
Vent Piping Guidelines
This unit is installed only as a Direct Vent gas central
furnace.
NOTE: In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged outdoors.
Intake and exhaust pipe sizing – Size pipe according to
Tables 4 and 5. Table 4 lists the minimum vent pipe lengths
permitted. Table 5 lists the maximum pipe lengths permitted.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination pipe
is sized to optimize the velocity of the exhaust gas as it exits
the termination. Refer to Table 6.
In some applications which permit the use of several different
sizes of vent pipe, a combination vent pipe may be used.
Contact Allied Air Technical Service for more information
concerning sizing of vent systems which include multiple
pipe sizes.
Use the steps in Figure 17 to correctly size vent pipe
diameter.
Figure 15
If this gas furnace replaces a furnace which was commonly vented
with another gas appliance, the size of the existing vent pipe for that
gas appliance must be checked. Without the heat of the original
furnace flue products, the existing vent pipe is probably oversized for
the single water heater or other appliance. The vent should be checked
for proper draw with the remaining appliance.
Piping Suspension Guidelines
NOTE: Isolate piping at the point where it exits the outside wall or
roof in order to prevent transmission of vibration to the structure.
Wall Thickness Guidelines
Figure 14
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