440 01 4300 00 9
Specifications subject to change without notice.
Ventilated Combustion Air Applications
When the furnace is installed using the ventilated combustion
air option, the attic or crawlspace must freely communicate with
the outdoor to provide sufficient air for combustion. 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.
All air for combustion is piped directly to the furnace from a
space that is well ventilated with outdoor air (such as an attic,
crawlspace, or equipment closet) and the space is well isolated
from the living space or garage. In addition, other gas
appliances installed in the space with the furnace may require
outside air for combustion. Follow the guidelines below to
insure that the roof or crawlspace walls have sufficient free
area to provide sufficient air for combustion and ventilation for
the furnaces. The guidelines below can be used to insure that
other gas appliances have sufficient air for combustion.
Provisions for adequate combustion, ventilation, and dilution air
must be provided in accordance with:
• U.S. Installations: Section 9.3 of the NFPA 54/ANSI
Z223.1−2009 , Air for Combustion and Ventilation and
applicable provisions of the local building codes.
• Canadian Installations: Part 8 of
CAN/CSA−B149.1−2010, Venting Systems and Air
Supply for Appliances and all authorities having
jurisdiction.
! CAUTION
FURNACE CORROSION HAZARD
Failure to follow this caution may result in furnace damage.
Air for combustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide, and
iodide. These elements can 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.
! WARNING
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. Make−up
air MUST be provided for the ventilation devices, in addition to
that required by the furnace. Refer to the Carbon Monoxide
Poisoning Hazard warning in the venting section of these
instructions to determine if an adequate amount of make−up air
is available.
Figure 6
Air for Combustion, Ventilation,
and Dilution for Outdoors
*Minimum dimensions of 3‐in. (76mm)
NOTE: Use any of the following combinations of openings:
A & B, C & D, D & E, F & G
L12F012
Figure 7 Combustion Air Pipe
12” MINIMUM
256.0 mm
TOP PLATE ATTACHMENT
COMBUSTION AIR PIPE
(ATTIC, CRAWL SPACE, OR
EQUIPMENT CLOSET ONLY.
See AIR FOR COMBUSTION
AND VENTILATION Section)
CASING SIDE ATTACHMENT
COMBUSTION AIR PIPE
(ATTIC, CRAWL SPACE, OR
EQUIPMENT CLOSET ONLY.
See AIR FOR COMBUSTION
AND VENTILATION Section)
Point elbow down towards
back of furnace
L12F014
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