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ACCEPTABLE
NOT ACCEPTABLE
Precautions must be taken to prevent condensate from
freezing inside the vent pipe. All vent piping exposed to
freezing temperatures must be insulated with 1/2" thick
closed cell foam. Inspect piping for leaks prior to installing
insulation.
Pipe Sizing
Consult table 4 to determine what diameter piping is
required for your installation. Lengths shown in table
4 apply to single pipe & two pipe installations. In a two
pipe installation do not add intake and vent pipe lengths
together. Both pipes would normally be equal in length, if
different, then the longest pipe must be within the limits of
table 4. It is preferable to up-size from 2" to 2.5" or 3" pipe
if the pipe length & elbow count are near maximum. This
will help avoid nuisance pressure switch opening caused
by prevailing winds & sudden changes in atmospheric
pressure.
0 - 4,999 FT ALTITUDE
Pipe Size
MODEL
(in)
2
*MVS960603BU
3
2
*MVS960805CU
3
5,000 - 7,500 FT ALTITUDE
Pipe Size
MODEL
(in)
*MVS960603BU
3
*MVS960805CU
3
TRANSITION NO LESS
THAN 45 TO HORIZONTAL
°
PLANE TO AVOID CREATING
A WATER TRAP IN VENT
PIPING.
Figure 5
NO TRANSITION ON
HORIZONTAL PLANE,
THIS CREATES A
WATER TRAP AND
RESTRICTS FLUE
GASES
Figure 6
Number of Elbows
1
2
3
4
5
6
90
85
80
75
70
65
158 151 144 137 130 123 116 109
55
50
45
40
35
30
151 144 137 130 123 116 109 102
Number of Elbows
1
2
3
4
5
6
100
93
87
81
75
69
80
73
67
61
55
49
Table 4
Vent Pipe Connection
The vent pipe outlet is sized to accept 2" pipe. Secure vent
pipe directly into the furnace fitting with the appropriate
glue. Alternately, a small section of 2" pipe may be glued
in the furnace socket and a rubber coupling installed
to allow removal for future service. Piping should be
routed in a manner to avoid contact with refrigerant lines,
metering devices, condensate drain lines, etc. If necessary,
clearances may be increased by creating an offset using
two 45° elbows (Figure 7).
Edges of sheet metal holes may be sharp. Use gloves as a
precaution when removing plugs.
Combustion Air Pipe Connection
If the furnace is being installed without a combustion air
pipe, a 90° elbow should be used on the combustion air
intake to guard against blockage.
On up flow / horizontal models, secure the combustion
air intake pipe to the air intake coupling using a rubber
coupling supplied with the furnace. The rubber coupling
may be omitted by inverting the intake coupling and gluing
pipe directly to it. Piping may also be glued to the intake
coupling in its original position by using a plastic coupling.
7
8
60
55
25
20
7
8
63
57
43
37
12
Increased Clearance Configuration
Figure 7
WARNING
VENT-DRAIN
Figure 8
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