Lennox ML193UH045P36B Unit Information page 22

Vent Piping Guidelines
NOTE - Lennox has approved the use of DuraVent
factured vent pipe and terminations as an option to PVC.
®
When using the PolyPro
vent pipe requirements stated in the unit installation in­
struction – minimum & maximum vent lengths, termination
clearances, etc. – apply and must be followed. Follow the
instructions provided with PoyPro by DuraVent venting
system for assembly or if requirements are more restrict­
ive. The PolyPro by Duravent venting system must also fol­
low the uninsulated and unconditioned space criteria listed
in table 16.
The ML193UH 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 out­
doors. 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 13 and . Count all elbows inside and outside the
14
home. Table 13 lists the minimum vent pipe lengths per­
mitted. Table lists the maximum pipe lengths permitted.
14
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 17.
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 accom­
modate 2" Schedule 40 vent pipe. In horizontal applica­
tions, 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 Applica­
tion Department for more information concerning sizing of
vent systems which include multiple pipe sizes.
Exhaust Pipe
12" max
of straight pipe
Horizontal Application
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 20
®
manu­
by DuraVent venting system the
12" Min.
MINIMUM VENT PIPE LENGTHS
ML193UH
MODEL
045, 070, 090, 110
135
*Any approved termination may be added to the minimum length listed.
Use the following steps to correctly size vent pipe diameter.
1
Which style termination
2
Standard or concentric?
3
How many elbows?
Count all elbows inside
4
and outside house.
5
What is the altitude of
6
the furnace installation?
Use table 14 or 15 to find
max intake or exhaust pipe
7
length. Includes all vent
pipe and elbows inside
and outside the house.
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups
and may block the terminations.
Page 22
TABLE 13
MIN. VENT LENGTH*
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
Piping Size Process
What is the
furnace capacity?
045, 070, 090,
110 or 135?
being used?
See table 12.
Which needs
most elbows?
Intake or
exhaust?
Desired pipe size?
2", 2-1/2", 3"
FIGURE 21
IMPORTANT