INSTALLATION INSTRUCTIONS
Gas Furnace: (F/G)9MVT, (F/G)9MXT, (F/G)9MXE
440 01 4001 05
9
Specifications subject to change without notice.
Air for Combustion and
Ventilation
Introduction
Direct Vent (2
−
pipe) Applications
When the furnace is installed as a direct vent (2-pipe) furnace,
no special provisions for air for combustion are required.
However, other gas appliances installed in the space with the
furnace may require outside air for combustion. Follow the
guidelines below to insure that other gas appliances have
sufficient air for combustion.
Non
−
Direct Vent (1
−
pipe) Applications
When the furnace is installed as a non-direct vent (1-pipe)
furnace, it will be necessary to insure there is adequate air for
combustion. Other gas appliances installed with the furnace
may also require air for combustion and ventilation in addition
to the amount of combustion air and ventilation air required for
the furnace. Follow the guidelines below to insure that the
furnace and other gas appliances have sufficient air for
combustion.
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
−
2012 , 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.
The requirements for combustion and ventilation air depend
upon whether or not the furnace is located in a space having a
volume of at least 50 cubic feet per 1,000 Btuh (4.8 cubic
meters per kW) input rating for all gas appliances installed in
the space.
•
Spaces having less than 50 cubic feet per 1,000 Btuh (4.8
cubic meters per kW) require the
OUTDOOR
COMBUSTION AIR
METHOD
.
•
Spaces having at least 50 cubic feet per 1,000 Btuh (4.8
cubic meters per kW) may use the
INDOOR
COMBUSTION AIR, STANDARD or KNOWN AIR
INFILTRATION
METHOD
.
Outdoor Combustion Air Method
1. Provide the space with sufficient air for proper
combustion, ventilation, and dilution of flue gases using
permanent horizontal or vertical duct(s) or opening(s)
directly communicating with the outdoors or spaces that
freely communicate with the outdoors.
2.
Figure 6
illustrates how to provide TWO OUTDOOR
OPENINGS, one inlet and one outlet combustion and
ventilation air openings to the outdoors.
a. One opening
MUST
commence within 12-in.
(300 mm) of the ceiling and the second opening
MUST commence within 12-in. (300 mm) of the floor.
b. Size openings and ducts per
Figure 6
and
Table 3
.
c. TWO HORIZONTAL DUCTS require 1 square inch
(25.4 square mm) of free area per 2,000 Btuh (1,100
mm
2
/kW) of combined input for all gas appliances in
the space per
Figure 6
and
Table 3
.
d. TWO OPENINGS OR VERTICAL DUCTS require 1
square inch (25.4 square mm)of free area per 4,000
Btuh (550 mm
2
/kW) for combined input of all gas
appliances in the space per
Figure 6
and
Table 3
.
3. ONE OUTDOOR OPENING requires:
a. 1 sq. in. (25.4 square mm)of free area per 3,000 Btuh
(734 mm
2
/kW) for combined input of all gas
appliances in the space per
Table 3
and
b. Not less than the sum of the areas of all vent
connectors in the space.
The opening shall commence within 12-in. (300 mm) of the
ceiling. Appliances in the space shall have clearances of at
least 1-in. (25 mm) from the sides and back and 6-in. (150 mm)
from the front. The opening shall directly communicate with the
outdoors or shall communicate through a vertical or horizontal
duct to the outdoors or spaces (crawl or attic) that freely
communicate with the outdoors.
