Lennox SLP98UHV Installation Instructions Manual page 14

Exhaust Pipe
Exhaust Pipe
Horizontal
Gas Furnace
12" ma x
of straight pip e
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 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 16
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.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze−ups
and may block the terminations.
TABLE 4
MINIMUM VENT PIPE LENGTHS
MIN. EQUIV.
SLP98UHV
VENT
MODEL
LENGTH
070, 090, 110
15 ft.*
135
*Any approved termination may be added to the minimum equivalent length
listed.
12" Min .
EXAMPLE
5 ft. plus 2 elbows of 2", 2−1/2"
or 3" diameter pipe
5 ft. plus 2 elbows of 3"
diameter pipe
Piping Size Process
furnace capacity?
1
045, 070, 090,
Which style termination
2
Standard or concentric?
most elbows?
3
How many elbows?
Count all elbows inside
4
and outside house.
Desired pipe size?
5
What is the altitude of
6
the furnace installation?
Use table 5 to find max
intake or exhaust pipe
7
length. Includes all vent
pipe and elbows inside
and outside the house.
Page 14
What is the
110 or 135?
being used?
See table 3.
Which needs
Intake or
exhaust?
2", 2−1/2", 3"
FIGURE 17