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Vent Piping Guidelines
The EL195UHE 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 10 and
11. Table 10 lists the minimum vent pipe
lengths permitted. Table 11 lists the maximum pipe lengths
permitted.
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 14.
In some applications which permit the use of several differ-
ent 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.
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 10
MINIMUM VENT PIPE LENGTHS
EL195UHE
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 9
Intake or
exhaust
Which needs
most elbows?
How many?
2", 2 1/2"
or 3"
Desired pipe size?
Use table 11 to find
max intake or
exhaust pipe length
for all altitudes.
FIGURE 20
7
Furnace capacity?
Is the intake air
taken from a
vetilated attic or
crawl space?
NO
YES
Use table 12 to find
max pipe length for
all altitudes
(exhaust pipe only)
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze−ups
and may block the terminations.
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