Lennox MERIT Series Installation Instructions Manual page 20

EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Roof Terminated
Exhaust Pipe
Ventilation
Furnace
Louvers
(Crawl space)
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm
hour of the total input rating of all equipment in the enclosure.
FIGURE 27
General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the out-
doors. The ML193DFE is then classified as a non-direct
vent, Category IV gas furnace.
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out-
doors. The ML193DFE is then classified as a direct vent,
Category IV gas furnace.
In both Non-Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the
absence of local codes, refer to the current National Fuel
Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current
Inlet Air
(Minimum
12 in.(305mm)
Above crawl
space floor)
*Intake Debris Screen Provided)
2
per 1.17kW) per
CSA-B149 Natural Gas and Propane Installation Codes in
Canada for details.
Position termination according to location given in FIG-
URE 29 or FIGURE 30. In addition, position termination
so it is free from any obstructions and 12" above the aver-
age snow accumulation.
At vent termination, care must be taken to maintain pro-
tective coatings over building materials (prolonged expo-
sure to exhaust condensate can destroy protective coat-
ings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of an outdoor AC unit because
the condensate can damage the painted coating.
NOTE - See table 9 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (0°C). If required
exhaust pipe should be insulated with 1/2" (13mm) Ar-
maflex or equivalent. In extreme cold climate areas, 3/4"
(19mm) Armaflex or equivalent may be necessary. Insu-
lation must be protected from deterioration. Armaflex with
UV protection is permissable. Basements or other en-
closed areas that are not exposed to the outdoor ambient
temperature and are above 32 degrees F (0°C) are to be
considered conditioned spaces.
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and may
block the terminations.
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of other
appliances shall not be less than 12 inches (305mm).
Page 20
IMPORTANT
IMPORTANT