507868-01
Page 16 of 48
Issue 1912
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
Route piping to outside of structure. Continue with
installation following instructions given in piping termination
section.
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
The exhaust vent pipe operates under positive pressure
and must be completely sealed to prevent leakage of
combustion products into the living space.
CAUTION
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
Table 6 and Table 7A through Table 7B. Table 6 lists the
minimum vent pipe lengths permitted. Table 7A and Table
7B list 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.
Table 6. Minimum Vent Pipe Lengths
Capacity
Min. Vent Length*
045, 070, 090
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
IMPORTANT
Use the following steps to correctly size vent pipe diameter.
Figure 22.
045, 070,
090
Standard or
Concentric?
See Table 5
Intake or
Exhaust?
1-1/2”,
2”, 2-1/2”
or 3”
Furnace capacity?
1
Which termination?
2
Which needs most
elbows?
3
How many?
4
Desired pipe size?
5
What is the altitude?
6
Use Table 7 to find
max pipe length.
7