Lennox SLP99UHV Series Unit Information page 49

In some applications which permit the use of several dif-
ferent sizes of vent pipe, a combination vent pipe may be
used. Contact Lennox' Application Department for assis-
tance in sizing vent pipe in these applications.
Use the steps in FIGURE 24 to correctly size vent pipe
diameter.
NOTE - It is acceptable to use any pipe size which fits
within the guidelines allowed in TABLE 24.
Horizontal Installation Offset Requirements
Exhaust Pipe
12" Max.
Horizontal
Gas Furnace
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 fitting,
unless the optional glueless vent adapter kit 17H92 is used..
NOTE - Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
FIGURE 23
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 23
MINIMUM VENT PIPE LENGTHS
SLP99UHV MIN.EQUIV. VENT
MODEL
070
090, 110
135
*Any approved termination may be added to the minimum equivalent
length listed. Two 45 degree elbows are the equivalent to one 90 de-
gree elbow.
Flue Coupling
The provided flue coupling must be attached (do not use
glue) to the exhaust coupling on the furnace top panel.
12" Min.
EXAMPLE
LENGTH
5 ft. plus 2 elbows of
1-/12", 2", 2-1/2" or
3" diameter pipe
5 ft. plus 2 elbows
15 ft*
of 2", 2-1/2" or 3"
diameter pipe
5 ft. plus 2 elbows of
3" diameter pipe
Use provided bands. See steps below and FIGURE 25.
1 - Remove the caution sticker from flue coupling .
2 - Fully insert flue coupling with both bands loosely
attached on the furnace exhaust coupling.
3 - Insert PVC exhaust pipe through flue coupling.
Ensure vent pipe is fully seated into exhaust
coupling. Tighten both top and bottom bands to 40
in lbs. See FIGURE 25.
Flue Coupling To Exhaust Coupling
PVC
Exhaust Pipe
Top Band
(torque to 40in-lbs)
Bottom Band
(torque to 40in-lbs)
Page 49
Piping Size Process
What is the
furnace capacity?
1
Which style termination
being used?
2
Standard or
concentric?.
Which needs
most elbows?
3
Intake or
exhaust?
How many elbows?
Count all elbows inside
4
and outside house.
Desired pipe size?
5
What is the altitude of
6
the furnace installation?
Find max intake or
exhaust pipe length.
7
Includes all vent pipe and
elbows inside and outside
the house.
FIGURE 24
Flue Couplig
Furnace
Exhaust Coupling
Furnace
Top Panel
FIGURE 25