Page 21
3 - Piping diameters should be determined according to
length of pipe run. See vent pipe specifications on
page 6. Locate intake piping upwind (prevailing wind)
from exhaust piping. To avoid re-circulation of exĆ
haust gas on roof terminations, end of exhaust pipe
must be higher than intake pipe.
Exhaust and intake exits must be in same pressure
zone. Do not exit one through the roof and one on the
side. Also, do not exit the intake on one side and the
exhaust on another side of the house or structure.
4 - Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to ilĆ
lustrations). Maximum separation is 3" (76mm) on
roof terminations and 6" (152mm) on side wall terĆ
minations.
5 - Exhaust piping must terminate straight out or up as
shown. In rooftop applications, a 2" X 1-1/2" reducer for
2" venting, 3" x 2" reducer for 3" venting must be used
on the exhaust piping after it exits the structure to imĆ
prove the velocity of exhaust away from the intake pipĆ
ing.
On roof terminations, the intake piping should termiĆ
nate straight down using two 90 elbows (See figure
26).
FIGURE 26
ROOF TERMINATION KIT
(15F75) LB-49107CC for 2 (51) Venting
(44J41) LB-65678A for 3 (76) Venting
UNCONDITIONED
ATTIC SPACE
1/2 (13) FOAM
INSULATION IN
UNCONDITIONED
SPACE
3 x 2 (76 x 51) OR
2 x 1-1/2 (51 x 38)
PVC REDUCER
3(76) MAX.
12 (305) ABOVE
AVERAGE SNOW
ACCUMULATION
3 (76) OR
2 (51) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8 (203) MIN
Inches(mm)
IMPORTANT
Do not use screens or perforated metal in intake
and exhaust terminations. Doing so will cause
freeze-ups and may block the terminations.
NOTE - If winter design temperature is below 32 F (0C), exĆ
haust piping must be insulated with 1/2" (13mm), Armaflex or
equivalent when run through unheated space. Do not leave
any surface area of exhaust pipe open to outside air; exterior
exhaust pipe must be insulated with 1/2" (13mm) Armaflex or
equivalent. In extreme cold climate areas, 3/4" (19mm) ArĆ
maflex or equivalent is recommended. Insulation on outside
runs of exhaust pipe must be painted or wrapped to protect
insulation from deterioration.
NOTE - During extremely cold temperatures, below
approximately 20F (6.67C), units with long runs of vent
pipe through unconditioned space, even when insulated,
may form ice in the exhaust termination that prevents the
unit from operating properly. Longer run times of at least 5
minutes will alleviate most icing problems. Also, a heating
cable may be installed on exhaust piping and termination
to prevent freeze-ups. Heating cable installation kit is
available from Lennox. See Condensate Piping section for
part numbers.
NOTE - Care must be taken to avoid re-circulation of exĆ
haust back into intake pipe.
6 - On field supplied terminations for side wall exits, exĆ
haust piping should extend a minimum of 12"
(305mm) beyond the outside wall. Intake piping
should be as short as possible. See figure 27.
FIGURE 27
1/2 (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
2 (51) PVC 1-1/2 (38) PVC
12 (305) MIN.
2 X 1-1/2
(51 x 38)
PVC REDUCER
1/2 (13) ARMAFLEX
INSULATION
6 (152)
MAXIMUM
2 (51) PVC
COUPLING
8 (203)
MINIMUM
OUTSIDE
WALL
Inches (mm)
TOP VIEW
WALL RING KIT
(15J74) LB-49107CB for 2 (50.8) Venting
7 - On field supplied terminations, a minimum separation
distance between the end of the exhaust pipe and the
end of the intake pipe is 8" (203mm).
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