35
COMBUSTION
AIR PIPE
BURNER
BOX
COMBUSTION AIR
INTAKE HOUSING
3/8" ID TUBE
TRAP
TO OPEN
DRAIN
3/16"
DRILL
4
″
(102
mm)
MIN
A93035
Fig. 40 -- Intake Housing Plug Fitting Drain
8. Install casing hole filler cap (factory--supplied in loose parts
bag) in unused combustion air pipe casing hole.
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 OVER--TIGHTEN 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 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. 40.
NOTE
:
(Direct Vent / 2--Pipe System ONLY). Moisture in
combustion air intake may be a result of improper termination.
Ensure combustion air pipe termination is similar to those as
shown in Fig. 36 so that it will not be susceptible to area where
light snow or others sources of moisture could be pulled in.
Combustion Air Termination -- Ventilated Combustion
Air Option
Provisions for adequate combustion, ventilation, and dilution air
must be provided in accordance with:
S
U.S. Installations: Section 9.3 NFPA 54/ANSI Z223.1--2006,
Air for Combustion and Ventilation and applicable provisions of
the local building codes.
S
Canadian Installations: Part 8 of CAN/CS--B149.1--05. Venting
Systems and Air Supply for Appliances and all authorities
having jurisdiction.
Combustion air is piped directly to the burner box on furnace using
the same materials used to vent the furnace. (See Table 5.) The
combustion air pipe is terminated in an attic or crawl space that is
well ventilated with OUTDOOR AIR and is well isolated from the
living space or garage. If the furnace is installed in a well ventilated
attic, crawlspace or other enclosure, the combustion air pipe can be
terminated in the same space.
UNIT CORROSION HAZARD
Failure to follow this caution may result in reduced furnace
component life.
Air for combustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide, and
iodide. These elements may corrode heat exchangers and
shorten furnace life. Air contaminants are found in aerosol
sprays, detergents, bleaches, cleaning solvents, salts, air
fresheners, and other household products.
CAUTION
!
The combustion air pipe cannot be terminated in attics or
crawlspaces that use ventilation fans designed to operate during the
heating season. If ventilation fans are present in these areas, the
combustion air pipe must terminate outdoors as a Direct Vent/
2--Pipe system.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal
injury or death.
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, attic exhaust fans or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Makeup air MUST be provided for the ventilation devices,
in addition to that required by the furnace. Refer to the
Carbon Monoxide Poisoning Hazard warning at the end of
this section to determine if an adequate amount of make--up
air is available.
!
WARNING
NOTE
: Combustion air pipe must have the same diameter as vent
pipe.
An attic or crawlspace may be considered a space that freely
communicates with the outdoors provided there are adequate
permanent ventilation openings directly to outdoors having free
area of at least 1--in.
2
/4,000 Btuh of total input rating for all gas
appliances in the space.
NOTE
: In determining the free area of an opening, the blocking
effect of the louvers, grilles, and screens must be considered. If the
free area of a louver or grille design is unknown, it may be
assumed that wood louvers have a 20 percent free area, and metal
louvers or grilles have a 60 percent free area. Screens, when used,
must not be smaller than 1/4--in. mesh. Louvers and grilles must be
constructed so they cannot be closed.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal
injury or death.
Many homes require air to be supplied from outdoors for
furnace combustion, ventilation, and dilution of flue gases.
The furnace combustion air supply must be provided in
accordance with this instruction manual.
!
WARNING
Attic terminations require at least (1) 90 degree elbow, with the
open end pointing horizontally or downward. The open end of the
elbow must be at least 12--in. (305 mm) above any insulation or
other materials. Screen the elbow with a wire mesh screen no
smaller than 3/8--inch square. (See Fig. 41.)
58MV
C