Page 18
NOTE - The exhaust collar on all models is sized to ac-
commodate 2” Schedule 40 vent pipe. In horizontal ap-
plications, any transition to exhaust pipe larger than 2”
must be made in vertical runs of the pipe. Therefore a 2”
elbow must be added before the pipe is transitioned to
any size larger than 2”. This elbow must be added to the
elbow count used to determine acceptable vent lengths.
Contact the Application Department for more information
concerning sizing of vent systems which include multiple
pipe sizes.
Horizontal Installation Offset Requirements
NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE -
ward unit. A minimum of 1/4” (6mm) drop for each 12” (305mm)
of horizontal run is mandatory for drainage.
NOTE - Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
12” ma x
of straight pip e
Exhaust Pipe
12” Min.
Horizontal
Gas Furnace
Figure 24
TABLE 4
MINIMUM VENT PIPE LENGTHS
ML195UH Model
MIN. VENT LENGTH*
040, -060, -080, 100
15 ft. or 5 ft. plus 2 elbows
or 10 ft. plus 1 elbow
*Any approved termination may be added to the minimum
length listed.
Use the following steps to correctly size vent pipe diam
-
eter.
1
2
3
4
5
6
Which style termination
being used?
Standard or concentric?
See table 3..
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
2” or 3”
Use table 5 or 6 to find
max intake or exhaust pipe
length. Includes all vent
pipe and elbows inside and
outside the house.
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
040, 060, 080, or
100?
Pipe Size Process
Figure 25
CAUTION
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
