Venting Practices; Vent Piping Guidelines - Lennox ML193DF Installation Instructions Manual

Venting Practices

Piping Suspension Guidelines
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
* See table 4 for allowable pipe.
NOTE - Isolate piping at the point where it exits the outside wall or
roof in order to prevent transmission of vibration to the structure.
Wall Thickness Guidelines
24" maximum
3/4" minimum
inside
FIGURE 19
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced
by ML193)
If an ML193DF furnace replaces a furnace which was com­
monly vented with another gas appliance, the size of the ex­
isting vent pipe for that gas appliance must be checked.
Without the heat of the original furnace flue products, the
existing vent pipe is probably oversized for the single water
heater or other appliance. The vent should be checked for
proper draw with the remaining appliance.
FIGURE 20
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.
Wall
outside
REPLACING FURNACE THAT
WAS PART OF A COMMON
VENT SYSTEM
WATER
HEATER
OPENINGS
(To Adjacent
Room)
Page 15
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 22 and 23)
Route piping to outside of structure. Continue with installa­
tion following instructions given in piping termination sec­
tion.
WARNING
Carbon Monoxide Poisoning Hazard
Cutting or altering exhaust or air intake pipes, which
are located in the blower compartment, could result
in Carbon Monoxide Poisoning or Death.
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
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 9.
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 6 and 7. Count all elbows inside and outside the
home. Table 6 lists the minimum vent pipe lengths per­
mitted. Table 7 lists the maximum pipe lengths permitted.
®
and
®
by DuraVent or