Page 21
1. In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clearance on
all sides of pipe through center of hole using a hanger.
2. When furnace is installed in a residence where unit is
shut down for an extended period of time, such as a
vacation home, make provisions for draining conden
sate collection trap and lines.
Exhaust Piping (Figures 21 and 22)
Route piping to outside of structure. Continue with installa
tion following instructions given in piping termination sec
tion.
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti
cal discharge through an existing unused stack is re
quired, insert PVC pipe inside the stack until the end
is even with the top or outlet end of the metal stack.
CAUTION
The exhaust vent pipe operates under positive pres
sure and must be completely sealed to prevent leak
age of combustion products into the living space.
Vent Piping Guidelines
NOTE -
Lennox has approved the use of DuraVent
®
manu
factured vent pipe and terminations as an option to PVC.
When using the PolyPro
®
by DuraVent venting system the
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 ML193DF can be installed as either a Non-Direct
Vent or a Direct Vent gas central furnace.
NOTE
- In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged outdoors. In
Non-Direct Vent installations, combustion air is taken from
indoors or ventilated attic or crawlspace and flue gases are
discharged outdoors.
Intake and exhaust pipe sizing --
Size pipe according to
tables 13 and 14. Count all elbows inside and outside the
home. Table 13 lists the
minimum
vent pipe lengths per
mitted. Table 14 lists the
maximum
pipe lengths permitted.
TABLE 13
MINIMUM VENT PIPE LENGTHS
ML193DF
MODEL
MIN. VENT LENGTH*
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.
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.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups
and may block the terminations.
Use the following steps to correctly size vent pipe diameter.
