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A
C
A
LTERNATE
OMBUSTION
(Upflow / Horizontal models only)
When using the alternate venting location, either in a
horizontal left side down installation or a vertical instal-
lation using down – venting, an alternate combustion air
opening can used. A locating dimple is located on the
right side of the furnace cabinet. The locating dimple is 1
7/8" measured from the front edge of the cabinet in line
with the knock out. To use the alternate combustion air
location:
1. Remove screws and combustion air flange from
cabinet.
2. Insert cabinet plug in unused combustion air hole.
3. Drill a pilot hole at the cabinet dimple (size dictated
by knockout tool used).
4. Use a knockout tool to create a 3" diameter hole
5. Install combustion air flange and secure with screws
removed in step one.
V
/F
P
L
ENT
LUE
IPE
ENGTHS AND
For installations at or above 7,000 feet altitude, use 3" vent-
ing. Refer to the following table for applicable length, elbows,
and pipe diameter for construction of the vent/flue pipe system.
The tee used in the vent/flue termination must be counted as
an elbow when determining the number of elbows in the piping
system.
Direct Vent (2 - Pipe) and Non-Direct Vent (1- Pipe)
Pipe
Model
Size
1
2 or 2 1/2
115
*MVM970603BNA*
3
137
2 or 2 1/2
115
*MVM970803BNA*
3
147
60
2 or 2 1/2
*MVM970804CNA*
3
120
2 or 2 1/2
40
*MVM971005CNA*
3
144
2 or 2 1/2
40
*MVM971205DNA*
3
144
2 or 2 1/2
95
*CVM970603BNA*
144
3
2 or 2 1/2
95
*CVM970803BNA*
3
144
2 or 2 1/2
60
*CVM970804CNA*
3
120
2 or 2 1/2
40
*CVM971005CNA*
3
103
1) Maximum allowable limits listed on individual lengths for inlet and flue
and NOT a combination.
2) Minimum requirement for each vent pipe is five (5) feet in length and
one elbow/tee.
3) Tee used in the vent/flue termination must be included when determin-
ing the number of elbows in the piping system.
4) 2 1/2" or 3" diameter pipe can be used in place of 2" diameter pipe.
P
IR
ROVISION
D
IAMETERS
(6)
Number of Elbows
2
3
4
5
6
110
105
100
95
90
130
123
116
109
102
110
105
100
95
90
140
133
126
119
112
55
50
45
40
35
113
106
99
92
85
35
30
25
20
15
137
130
123
116
109
35
30
25
20
15
137
130
123
116
109
90
85
80
75
70
137
130
123
116
109
90
85
80
75
70
137
130
123
116
109
55
50
45
40
35
113
106
99
92
85
35
30
25
20
15
96
89
82
75
68
5) Increased Clearance Configurations using (2) 45 deg. elbows should
be considered equivalent to one 90 deg. elbow.
6) One 90° elbow should be secured to the combustion air intake connec-
tion.
7) For installations at or above 7,000 feet altitude, use 3" venting.
V
/F
P
ENT
LUE
NOTE: If either a 90 degree or 45 degree elbow is used for
termination, it must be pointed downward.
The vent/flue pipe may terminate vertically, as through a
roof, or horizontally, as through an outside wall.
Vertical vent/flue pipe terminations should be as shown in
the following figure. Refer to Vent/Flue Pipe and Combustion
Air Pipe - Termination Locations for details concerning loca-
tion restrictions. The penetration of the vent through the
roof must be sealed tight with proper flashing such as is used
with a plastic plumbing vent.
Horizontal vent/flue pipe terminations should be as shown in the
following figure. Refer to Vent/Flue Pipe and Combustion Air
Pipe - Termination Locations for details concerning location re-
strictions. The wall penetration should be sealed with sili-
cone caulking material.
NOTE: Terminate both pipes in the same pressure zone
(same side of roof, no major obstacles between pipes,
etc.).
7
8
85
80
COMBUSTION AIR INTAKE
95
88
(OPTIONAL)
*Not required for
85
80
singl e pipe installation
105
98
30
25
78
71
10
5
102
95
10
5
102
95
12" MIN TO ROOF OR HIGHEST
65
60
ANTICIPATED SNOW LEVEL
102
95
65
60
102
95
30
25
78
71
10
5
61
54
T
IPE
ERMINATIONS
Figure 13
ELBOWS
STRAIGHT
Figure 14
TEE (OPTIONAL)
12" MIN
HEIGHT DIFFERENCE
BETWEEN
INTAKE AND VENT
21
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