F97CMN and G97CMN: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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A05091
Fig. 39 – Vent Pipe Termination for Non-Direct Vent and Ventilated Combustion Air System
Table 10 – Vent Termination Kit for Direct Vent (2-pipe) Systems
Direct Vent / 2-Pipe System
In a direct-vent (2-pipe) system, all air for combustion is taken directly
from outdoor atmosphere, and all flue products are discharged to outdoor
atmosphere. Combustion-air and vent pipes must terminate together in
the same atmospheric pressure zone, either through the roof (preferred)
or a sidewall. See
for references to clearances required by
National code authorities.
Ventilated Combustion Air Systems
In a ventilated combustion air option, the vent terminates and discharges
the flue products directly to the outdoors similar to a direct vent system.
See
for references to clearances required by National code
authorities.
All air for combustion is piped directly to the furnace from a space that is
well ventilated with outdoor air (such as an attic or crawl space) and the
space is well isolated from the living space or garage. Combustion air
requirements for this option are the same as the requirements for
providing outside air for combustion for a single pipe vent system. Refer
to the “Air For Combustion and Ventilation” Section.
Vent and
Combustion Air Pipe
Diameters
Approved Two-Pipe Termination Fittings
Allowable Concentric
Vent Kit
1 1/2-in.
(38 mm)
2-in.
(51 mm)
2 1/2-in.
(64 mm)
3-in.
(76-mm)
4-in.
(102 mm)
1 1/2-in. (38 mm)
No
Yes
No
No
No
2-in. (51 mm)
2-in. (51 mm)
No
Yes
No
No
No
2-in. (51 mm)
2 1/2-in. (64 mm)
No
No
No
Yes
No
2-in. (51 mm)
3-in. (76 mm)
3-in. (76-mm)
No
No
No
Yes
No
3-in. (76 mm)
4-in. (102 mm)
No
No
No
Yes
Yes
3-in. (76 mm)
NOTICE
!
OPTIONAL CONFIGURATION FOR COMBUSTION
AIR INLET PIPE
In applications where there is a risk of excessive moisture entering the
combustion air inlet pipe, a moisture trap may be added to the inlet pipe
to help prevent moisture from entering the furnace from the combustion
air inlet pipe, see
When sizing venting systems, the equivalent length of the optional inlet
pipe moisture trap must be taken into account.
