Page 16
Vent Piping Guidelines
The 92AF1UH/95AF1UH 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 out-
doors and flue gases are discharged outdoors.
Intake and exhaust pipe sizing −−
Size pipe according to
tables 4 and
5
. Table 4 lists the
minimum
vent pipe lengths
permitted. Table
5
lists the
maximum
pipe lengths per-
mitted.
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 7.
In some applications which permit the use of several differ-
ent sizes of vent pipe, a combination vent pipe may be
used. Contact Application Department for assistance in
sizing vent pipe in these applications.
NOTE
− The exhaust collar on all models is sized to ac-
commodate 2" Schedule 40 vent pipe. In horizontal ap-
plications, 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.
FIGURE 19
12" max
of straight pipe
Exhaust Pipe
12" Min.
NOTE
− Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE −
All horizontal runs of exhaust pipe must slope back to-
ward unit. A minimum of 1/4" (6mm) drop for each 12" (305mm)
of horizontal run is mandatory for drainage.
NOTE
− Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
Horizontal Application
TABLE 4
MINIMUM VENT PIPE LENGTHS
92AF1UH/95AF1UH
MODEL
MIN. VENT LENGTH*
045, 070, 090, 110, 135
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
or 135 btuh
Which termination?
Standard or
Concentric?
See table 3
Intake or
exhaust
Which needs
most elbows?
How many?
2", 2 1/2"
or 4"
Desired pipe size?
Use table 5 to find
max. intake or
exhaust pipe length.
FIGURE 20
What is the altitude?
7
Furnace capacity?
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze−ups
and may block the terminations.
