Lennox ML195UH 045XP24B, Unit Information

Page 36

Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations

NOTE

 - In Direct Vent installations, combustion air is taken

from outdoors and flue gases are discharged to outdoors.

Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In at­
tic or closet installations, vertical termination through the
roof is preferred. Figures 38 through 45 show typical
terminations.
 1. Intake and exhaust terminations are not required to be

in the same pressure zone. You may exit the intake on
one side of the structure and the exhaust on another
side (figure  39). You may exit the exhaust out the roof
and the intake out the side of the structure (figure 40).

 2. Intake and exhaust pipes should be placed as close

together as possible at termination end (refer to il­
lustrations). Maximum separation is 3” (76mm) on roof
terminations and 6” (152mm) on side wall termina­
tions.

NOTE

 - When venting in different pressure zones, the

maximum separation requirement of intake and ex­
haust pipe DOES NOT apply.

 3. On roof terminations, the intake piping should termi­

nate straight down using two 90° elbows (See figure
38).

 4. Exhaust piping must terminate straight out or up as

shown. A reducer may be required on the exhaust pip­
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 17.

TABLE 17

EXHAUST PIPE TERMINATION SIZE REDUCTION

ML195UH

MODEL

Exhaust Pipe Size

Termination

Pipe Size

*045 and 070

2” (51mm), 2-1/2” (64mm),

3” (76mm)

1-1/2” (38mm)

*090

2” (51mm)

110

2” (51mm)

135

3” (76mm)

2” (51mm)

*ML195UH-045, -070 and -090 units with the flush mount
termination must use the 1 1/2”accelerator supplied with
the kit.

NOTE

 - Care  must be taken to avoid recirculation of ex­

haust back into intake pipe.

 5. On field supplied terminations for side wall exit, ex­

haust piping may extend a maximum of 12 inches
(305mm) for 2” PVC and 20 inches (508mm) for 3”
(76mm) PVC beyond the outside wall. Intake piping
should be as short as possible. See figure 46.

 6. On field supplied terminations, a minimum distance

between the end of the exhaust pipe and the end of the
intake pipe without a termination elbow is 8” and a
minimum distance of 6” with a termination elbow. See
figure 46.

FIGURE 38

UNCONDITIONED

ATTIC SPACE

1/2” (13mm) FOAM

INSULATION IN

UNCONDITIONED

SPACE

SIZE TERMINATION

PIPE PER TABLE 17.

3”(76mm) MAX.

12” (305mm) ABOVE

AVERAGE SNOW

ACCUMULATION

3” (76mm) OR

2” (51mm) PVC

PROVIDE SUPPORT

FOR INTAKE AND

EXHAUST LINES

8” (203mm) MIN

Inches(mm)

DIRECT VENT ROOF TERMINATION KIT

(15F75 or 44J41)

FIGURE 39

Exhaust

Pipe

Furnace

Exiting Exhaust and Intake Vent

(differen pressure zones)

Inlet Air

(Minimum 12 in.

305 MM) above

grade or snow

accumulation

FIGURE 40

Roof Terminated

Exhaust Pipe

Furnace

Exiting Exhaust and Intake Vent

(different pressure zones)

Inlet Air

(Minimum 12 in.

305 MM) above

grade or snow

accumulation

 7. If intake and exhaust piping must be run up a side wall

to position above snow accumulation or other ob­
structions, piping must be supported. At least one
bracket must be used within 6” from the top of the el­
bow and then every 24” (610mm) as shown in figure
46, to prevent any movement in any direction. When
exhaust and intake piping must be run up an outside
wall, the exhaust piping must be terminated with pipe
sized per table 17.The intake piping may be equipped
with a 90° elbow turndown. Using turndown will add 5
feet (1.5m) to the equivalent length of the pipe.