Venting Practices - Lennox MERIT Series Installation Instructions Manual

Venting Practices

Piping Suspension Guidelines
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
* See Piping and Fittings Specifications table
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
n i s d i e
FIGURE 20
REPLACING FURNACE THAT WAS PART OF A
COMMON VENT SYSTEM
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced)
If replacing a furnace which was
commonly vented with another gas appliance, the size
of the existing 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 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.
Wall
o u s t d i e
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
condensate collection trap and lines.
Exhaust Piping (FIGURE 23 and FIGURE 24)
Route piping to outside of structure. Continue with instal-
lation following instructions given in piping termination
section.
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 vertical
discharge through an existing unused stack is required,
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 pressure
and must be completely sealed to prevent leakage of
combustion products into the living space.
Vent Piping Guidelines
NOTE - Lennox has approved the use of DuraVent® and
Centrotherm manufactured vent pipe and terminations
as an option to PVC. When using the PolyPro® by Du-
raVent or InnoFlue® by Centrotherm 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 and Inno-
Flue by Centrotherm venting system for assembly or if re-
quirements are more restrictive. The PolyPro by Duravent
and InnoFlue by Centrotherm venting system must also
follow the uninsulated and unconditioned space criteria
listed in TABLE 9.
The ML193DFE 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
TABLE 6 (minimum) and TABLE 7 (maximum). Count all
elbows inside and outside the home.