Carrier 58MTB Installation, Start-Up, And Operating Instructions Manual page 34

Table 10—Maximum Allowabl Exposed Vent Pipe Length (ft) With and Without Insulation in
WINTER DESIGN
UNIT
TEMPERATURE
SIZE
060
080
100
120
* Pipe length (ft) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe length
as specified in Table 11.
† Insulation thickness based on R value of 3.5 per in.
Attachment of Combustion Air Pipe
1. Determine location of combustion air intake pipe connection
to combustion air intake housing as shown in Fig. 38 for
application.
2. Reposition combustion air intake housing plug fitting in
appropriate unused intake housing connection.
3. Install combustion-air pipe grommet (factory-supplied in
loose parts bag) into selected furnace casing combustion-air
pipe hole. (See Fig. 40.)
4. Insert assembled combustion air inlet pipe into intake housing
as shown in Fig. 38.
5. Drill a 1/8-in. hole in 2-in, combustion air pipe using the hole
in intake housing as a guide.
6. Install a field-supplied No. 6 or No. 8 sheet metal screw into
combustion air pipe.
7. Install casing hole filler cap (factory-supplied in loose parts
bag) in unused combustion air pipe casing hole.
NOTE: Do not attach combustion air intake pipe permanently to
combustion air intake housing since it may be necessary to remove
pipe for service of burner box components or flame sensor.
Attachment of Combustion Air Intake Housing Plug Fitting
The combustion-air intake plug fitting must be installed in unused
combustion air intake housing. This fitting must be attached by
using RTV sealant, or by drilling a 1/8-in. hole in fitting, using
hole in intake housing as a guide. Install a field-supplied No. 6 or
No. 8 sheet metal screw.
NOTE: DO NOT OVERTIGHTEN SCREW. Breakage of intake
housing or fitting may cause air leakage to occur.
A plugged drain connection has been provided on this fitting for
use when moisture is found in combustion air intake pipe and
combustion box. If use of this drain connection is desired, drill out
Winter Design Temperature Ambient*
MAX PIPE
DIAMETER
(°F) (IN.)
20 2
0 2
-20 2
20 2
0 2
-20 2
20 2.5
0 2.5
-20 2.5
20 2.5
0 2.5
-20 2.5
20 3
0 3
-20 3
20 3
0 3
-20 3
20 4
0 4
-20 4
WITHOUT
INSULATION
44
21
20
55
30
16
58
29
14
40
38
21
63
30
12
70
38
19
65
26
5
fitting's tap plug with 3/16-in. drill and connect a field-supplied
3/8-in. tube. This tube should be routed to open condensate drain
for furnace and A/C (if used), and should be trapped, as shown in
Fig. 42.
NOTE: (Direct Vent/2-Pipe System ONLY). Moisture in com-
bustion air intake may be a result of improper termination. Ensure
combustion air pipe termination is similar to those as shown in Fig.
44 so that it will not be susceptible to area where light snow or
others sources of moisture could be pulled in.
→
VENT PIPE
General
Furnace vent connection must be attached as shown in Fig. 38.
CARBON MONOXIDE POISONING AND PROPERTY
DAMAGE HAZARD
Failure to follow this warning could result in property
damage, personal injury, or death.
Vent pipes must be airtight.
NOTE: A 2-in. diameter pipe must be used within the furnace
casing. Make all pipe diameter transitions outside furnace casing
per Fig. 41.
The minimum vent pipe length for these furnaces is 5 ft. Short pipe
lengths (5-8 ft) may discharge condensate droplets. These conden-
sate droplets may be undesirable. A 12-in. minimum offset pipe
section is recommended to reduce excessive condensate droplets
from exiting vent pipe outlet. (See Fig. 43.)
Attachment of Vent Pipe
1. Determine vent pipe diameter and maximum pipe lengths
using Table 12.
34
WITH 3/8–IN. OR
THICKER INSULATION†
70
70
57
55
55
55
70
70
67
40
40
40
70
70
70
70
70
70
70
70
65