Page 17
The ML193UHE 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 ue gases are discharged out-
doors. In Direct Vent installations, combustion air is taken
from outdoors and ue gases are discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
TABLE 4 and TABLE 5. Count all elbows inside and outside
the home. 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 stan-
dard roof and wall terminations described in section Ex-
haust 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 8.
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.
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.
Horizontal Installation Offset Requirements
NOTE - Exhaust pipe MUST be glued to furnace exhaust fitting,
unless the optional glueless vent adapter kit 17H92 is used..
NOTE -
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.
Exhaust Pipe
Horizontal
Gas Furnace
12” Min.
12” Max.
FIGURE 23
NOTE - Lennox oers a glueless vent adapter kit 17H92
as an option for exhaust exiting at the furnace top cap
coupling. If the kit is not used then the exhaust pipe MUST
be glued to the furnace exhaust tting.
1
2
3
4
5
6
Which style termination
being used?
Standard or
concentric?.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
Find max intake or
exhaust pipe length.
Includes all vent pipe and
elbows inside and outside
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
FIGURE 24
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
ML193UHE Model MIN. VENT LENGTH*
030, 045, -070, -090, 110
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. Two 45 degree elbows are the equivalent to one
90 degree elbow.
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