INSTALLATION INSTRUCTIONS
Gas Furnace: (F/G)9MVT, (F/G)9MXT, (F/G)9MXE
440 01 4001 05
43
Specifications subject to change without notice.
Figure 50
Vent Pipe Termination for Non
−
Direct Vent and Ventilated Combustion Air System
Abandoned masonry
used as raceway
(per code)
12 in. (305 mm) min. from
overhang or roof
Maintain 12 in. (305mm)
minimum clearance
above highest anticipated
snow level or grade
whichever is greater.
Side wall termination
with 2 elbows (preferred)
12 in. min. (305 mm)from
overhang or roof
Maintain 12 in. (305mm)
minimum clearance
above highest anticipated
snow level or grade
whichever is greater
6 in. (152mm) minimum clearance
between wall and end of vent pipe.
10 in. (254mm) maximum pipe length
Sidewall Termination
with Straight Pipe (preferred)
Roof Termination (Preferred)
Vent
Maintain 12 in
.
minimum clearance
above highest anticipated
snow level maximum of
24 in. (610mm) above roof
.
90
°
(305mm)
A05091
Size the Vent and Combustion Air Pipes
General
Vent or Combustion Air
Pipe Diameters
Approved 2
−
pipe
termination fittings
2
−
in.
3
−
in.
4
−
in.
1 1/2
−
in.
X
N/A
N/A
2
−
in.
X
N/A
N/A
2 1/2
−
in.
N/A
X
N/A
3
−
in.
N/A
X
N/A
4
−
in.
N/A
X
X
Note:
Optional accessory 2
−
pipe termination brackets are
sized for 2
−
in. and 3
−
in. Pipe. If a termination bracket is
required for a 4
−
in. termination, field fabricate the necessary
brackets and clamps.
Furnace combustion air and vent pipe connections are sized
for 2-in. (50 mm ND) PVC/ABS DWV pipe. The combustion air
and vent pipe connections also accommodate 60mm
polypropylene venting systems with outside diameters of
approximately 60 mm (2
−
3/8 inches). Any pipe diameter
change should be made outside furnace casing in vertical pipe.
Any change in diameter to the pipe must be made as close to
the furnace as reasonably possible.
The Maximum Vent Length for the vent pipe and combustion air
pipe (when used) equals the Maximum Equivalent Vent Length
(MEVL) in
Table 14
or
Table 16
, minus the number of fittings
multiplied by the deduction for each type of fitting used from
Table 15
.
NOTICE
OPTIONAL CONFIGURATION FOR COMBUSTION
AIR INLET PIPE
In applications where there is a risk of excessive mois-
ture entering the combustion air inlet pipe, a moisture
trap may be added to the inlet pipe to help prevent
moisture from entering the furnace from the combus-
tion air inlet pipe. See
Figure 51
.
When sizing venting systems, the equivalent length of
the optional moisture trap (15 feet/5 M) must be taken
into account
Optional Combustion Air Inlet
Moisture Trap
As an option to prevent moisture from trickling into the furnace
vestibule, a trap can be installed in the intake air pipe near the
furnace. Connecting a drain line to the trap is optional as trace
amounts of moisture will evaporate into the intake air stream. If
the combustion air inlet is located near a moisture exhaust
duct, or there are other concerns of excessive moisture being
drawn into the combustion air inlet, it is encouraged to connect
a drain line to the trap.
The trap can be constructed from a running tee of the same
diameter of the intake air pipe with EITHER a removable cap
attached to a 6-inch long pipe connected to the tee or the
External vent Trap Kit to help prevent contaminants from
entering the furnace. See
Figure 51
.
The External Vent Trap Kit accessory may be used as a trap for
the combustion air inlet pipe if a large amount of moisture must
be removed. The drain line may be connected to the same
drain as the furnace condensate and the evaporator coil
condensate line ONLY if the inlet air trap drain and the
evaporator coil drain empty into an open segment of pipe
above the drain, See
Figure 12
. When using the External Vent
