Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual page 24

VENT PIPE
HORIZONTAL TO ROOF
COMBUSTION-AIR PIPE
VERTICAL TO ROOF
Combustion-Air and Vent Pipe Diameter
Determine combustion-air and vent pipe diameter.
1. Using Table 6, individually determine the combustion-air and
vent pipe diameters. Pick the larger of these 2 pipe diameters
and use this diameter for both combustion-air and vent pipes.
2. When installing vent systems of short pipe length, use the
smallest allowable pipe diameter. Do not use pipe size greater
than required or incomplete combustion, flame disturbance, or
flame sense lockout may occur.
NOTE: Do not count elbows or pipe sections in terminations or
within furnace. See shaded areas in Fig. 30, 31, 32, 33, and 34.
12 " MIN
COMBUSTION-AIR PIPE
12 " MIN
NOTE: A 12 In. minimum offset pipe section is recommended with
short (5 to 8 ft) vent systems. This recommendation is to reduce
excessive condensate droplets from exiting the vent pipe.
Fig. 28—Short Vent (5 to 8 Ft) System
VENT PIPE
HORIZONTAL TO SIDEWALL
COMBUSTION-AIR PIPE
VENT PIPE
VERTICAL TO SIDEWALL
EXAMPLE: An 036080 size furnace located in Indianapo-
lis, elevation 650 ft above sea level, could be installed in an
application requiring 3 elbows and 32 ft of vent pipe, along
with 5 elbows and 34 ft of combustion-air pipe. Table 6
indicates this application would allow a 2-in. diameter vent
pipe, but require a 2-1/2 in. diameter combustion air pipe
(2-in. pipe is good for 35 ft with 3 elbows, but only 30 ft
with 5 elbows). Therefore, 2-1/2 in. diameter pipe must be
used for both vent and combustion-air pipes since larger
required diameter must always be used for both pipes. If
same installation were in Albuquerque, elevation 5250 ft
above sea level, installation would require 2-1/2 in. vent
pipe and combustion-air pipe. At 5001- to 6000-ft eleva-
tion, 2-in. pipe is only good for 17 ft with 5 elbows, and
2-1/2 in. pipe is good for 70 ft with 5 elbows.
Combustion-Air and Vent Pipe Attachment
NOTE: All pipe joints must be watertight except attachment of
combustion-air pipe to inlet housing connection, since it may be
necessary to remove pipe for servicing.
1. Attach combustion-air pipe as follows:
a. Determine location of combustion-air intake pipe connec-
tion to combustion-air intake housing as shown in Fig. 27
for application.
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12 " MIN
COMBUSTION-AIR PIPE
12 " MIN
VENT PIPE
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