Vent Piping Guidelines; Minimum Vent Pipe Lengths - Lennox EL296DF045XV36B Unit Information

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Vent Piping Guidelines

NOTE - Lennox has approved the use of DuraVent
Centrotherm manufactured vent pipe and terminations as
an option to PVC. When using the PolyPro
®
InnoFlue
by Centrotherm venting system the vent pipe re­
quirements stated in the unit installation instruction – min­
imum & maximum vent lengths, termination clearances,
etc. – apply and must be followed. Follow the instructions
provided with PoyPro by DuraVent and InnoFlue by Cen­
trotherm venting system for assembly or if requirements
are more restrictive. The PolyPro by Duravent and In­
noFlue by Centrotherm venting system must also follow
the uninsulated and unconditioned space criteria listed in
table 22.
The EL296DFV 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 or ventilated attic or crawlspace and flue
gases are discharged outdoors. In Direct Vent installations,
combustion air is taken from outdoors and flue gases are
discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
tables 20 and 21. Count all elbows inside and outside the
home. Table 20 lists the minimum vent pipe lengths per­
mitted. Table 21 lists the maximum pipe lengths permitted.
TABLE 20

MINIMUM VENT PIPE LENGTHS

EL296DFV
MODEL
045, 070, 090, 110
*Any approved termination may be added to the minimum length listed.
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 24.
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.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups
and may block the terminations.
NOTE - It is acceptable to use any pipe size which fits within
the guidelines allowed in table 21.
NOTE - All horizontal runs of exhaust pipe must slope back
toward unit. A minimum of 1/4" (6mm) drop for each 12"
(305mm) of horizontal run is mandatory for drainage.
®
and
®
by DuraVent or
MIN. VENT LENGTH*
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
Page 37
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.
NOTE - If right side venting option is used, you must include
the elbow at the furnace in the elbow count. If transitioning
to 3" dia pipe, this elbow equates to 20' of equivalent vent
length for all models.
Use the following steps to correctly size vent pipe diameter.
Piping Size Process
What is the
furnace capacity?
1
045, 070, 090,
110 or 135?
Which style termination
being used?
2
Standard or concentric?
See table 19.
Which needs
most elbows?
3
Intake or
exhaust?
How many elbows?
Count all elbows inside
4
and outside house.
Desired pipe size?
5
2", 2-1/2", 3"
What is the altitude of
6
the furnace installation?
Use table 21 or 23 to find
max intake or exhaust pipe
7
length. Includes all vent
pipe and elbows inside
and outside the house.
FIGURE 22

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