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506725-01 Page 15 of 48
Issue 1109
Vent Piping Guidelines
This gas furnace can be installed as either a Non-Direct
Vent or a Direct Vent gas central furnace.
NOTE: In non-Direct Vent installations, combustion air is
taken from indoors and flue gases are discharged outdoors.
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
6 and 7. Table 6 lists the minimum vent pipe lengths
permitted. Table 7 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.
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 assistance in sizing
vent pipe in these applications.
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 trap and lines.
Exhaust Piping (Figure 20)
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
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
IMPORTANT
TABLE 6
MINIMUM VENT PIPE LENGTHS
A95DF, 95G1DF, A93DF, & 92G1DF
MODELS
MIN. VENT LENGTH*
045, 070, 090, 110
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
*Any approved termination may be added to the minimum length listed.
Use the following steps to correctly size vent pipe diameter.
1
2
3
4
5
6
045, 070,
090, 110
Which termination?
Standard or
Concentric?
See Table 5
Intake or
exhaust
Which needs
most elbows?
How many?
2", 2 1/2"
or 3"
Desired pipe size?
Use Table 7 to nd
max intake or exhaust
pipe length.
FIGURE 19
What is the altitude?
7
Furnace capacity?