COMFORT-AIRE Century GDD95C Series, Installation Instructions Manual

Page: 15 / 53

507735-03 Page 15 of 53 Issue 1933
Exhaust Piping
See Figure 22
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.
3. 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 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 Comfort-Aire / Century for assistance in
sizing vent pipe in these applications.
Table 6. Minimum Vent Pipe Length
Capacity 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.
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 21.
045, 070,
090, 110
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