Carrier 58MCA Installation, Start-Up, And Operating Instructions Manual page 21

FURNACE
NOT IN
HORIZONTAL
SECTION
Fig. 27—Combustion-Air and Vent Pipe Diameter
Transition Location and Elbow Configuration
Fig. 28—Combustion-Air and Vent Pipe Connec-
tions
When combustion-air pipe is installed above a suspended
ceiling, pipe must be insulated with 3/8-in. thick Armaflex-
type insulation. Combustion-air pipe should also be insulated
when it passes through warm, humid space.
When vent pipe is exposed to temperatures below freezing,
such as when it passes through an unheated space or when a
chimney is used as a raceway, pipe must be insulated as
shown in Table 6 with Armaflex-type insulation.
PIPE DIAMETER
TRANSITION IN
VERTICAL SECTION
A93034
A93083
Combustion air must not be taken from inside structure
because that air is frequently contaminated by halogens,
which include fluorides, chlorides, bromides, and iodides.
These elements are found in aerosols, detergents, bleaches,
cleaning solvents, salts, air fresheners, adhesives, paint, and
other household products. Locate combustion-air inlet as far
as possible from swimming pool and swimming pool pump
house.
Solvent cements are combustible. Keep away from heat,
sparks, and open flame. Use only in well-ventilated areas.
Avoid breathing in vapor or allowing contact with skin or
eyes. Failure to follow this warning could result in fire,
property damage, personal injury, or death.
All combustion-air and vent pipes must be airtight and
watertight. Pipes must also terminate exactly as shown in Fig.
31, 32, 33, 34, or 35. Failure to follow this warning could
result in property damage, personal injury, or death.
NOTE: The minimum combustion-air and vent pipe length (each)
for these furnaces is 5 ft. Short pipe lengths (5-8 ft) may discharge
water droplets. These droplets may be undesirable, and a 12-in.
minimum horizontal pipe section is recommended, as shown in
Fig. 29, to reduce excessive droplets from exiting vent pipe outlet.
COMBUSTION-AIR AND VENT PIPE DIAMETER
Determine combustion-air and vent pipe diameter.
1. Using Table 5, determine preliminary combustion-air pipe
diameter.
2. Using Table 5, determine preliminary vent pipe diameter.
3. Use largest diameter pipe determined in 1. and 2. above for
both pipes.
NOTE: Do not count elbows or pipe sections in terminations or
within furnace. See shaded areas in Fig. 31, 32, 33, 34, and 35.
EXAMPLE:
An 080-12 size furnace located in Indianapolis, 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 5 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 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 elevation, 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. 28
for application.
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