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Vent Piping Guidelines
NOTE: GE Appliances has approved the use of DuraVent
and Centrotherm manufactured vent pipe and terminations
as an option to PVC. When using the PolyPro
or InnoFlue
by Centrotherm venting system the vent pipe
®
requirements stated in the unit installation instruction –
minimum & maximum vent lengths, termination clearances,
etc. – apply and must be followed. Follow the instructions
provided with PoyPro by DuraVent and InnoFlue by
Centrotherm venting system for assembly or if requirements
are more restrictive. The PolyPro by Duravent and InnoFlue
by Centrotherm venting system must also follow the
uninsulated and unconditioned space criteria listed in Table
21.
The NF97UM is installed as a Direct Vent gas central
furnace only.
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
Table 20 through Table 23B. Count all elbows inside and
outside the home. Table 20 lists the minimum vent pipe
lengths permitted. Table 23A through Table 23B 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. Refer to Table 22.
In some applications which permit the use of several
different sizes of vent pipe, a combination vent pipe may be
used. Contact GE Appliances Application Department for
assistance in sizing vent pipe in these applications.
NOTE: The exhaust collar on all models is sized to
accommodate 2" Schedule 40 vent pipe. In horizontal
applications, any transition to exhaust pipe larger than 2"
must be made in vertical runs of the pipe. Therefore a 2"
elbow must be added before the pipe is transitioned to any
size larger than 2". This elbow must be added to the elbow
count used to determine acceptable vent lengths. Contact
the Application Department for more information concerning
sizing of vent systems which include multiple pipe sizes. See
Figure 31.
NOTE: It is acceptable to use any pipe size which fits within
the guidelines allowed in Table 23A and Table 23B.
31-5000723 Rev. 0
®
Horizontal
Gas Furnace
by DuraVent
®
NOTE -
ward unit. A minimum of 1/4" (6mm) drop for each 12" (305mm)
of horizontal run is mandatory for drainage.
NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE - Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
Figure 23. Horizontal Installation Offset Requirements
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
Model
70
90
110
135
Page 37
Exhaust Pipe
12" Max.
IMPORTANT
Min. Equiv.
Vent Length
5 ft. plus 2 elbows of 1-1/2", 2", 2-1/2"
or 3" diameter pipe
5 ft. plus 2 elbows of 2", 2-1/2"
or 3" diameter pipe
15 ft.*
5 ft. plus 2 elbows of 2-1/2"
or 3" diameter pipe
5 ft. plus 2 elbows of 3"
diameter pipe
Table 20.
12" Min.
Example
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