6
Furnace
12" Max.
Water
Heater
Vent or
Chimney
NOTES:
Each opening must
be at least 100 sq. in.
or 1 sq. in. per 1,000
Btuh of total input rating,
whichever is greater.
Openings must start at
no more than 12 inches
from the top and bottom
of the enclosure.
12” Max.
See
Notes
See Notes
Figure 1. Combustion Air Drawn from Inside
Total Input Rating
(Btuh)
Minimum Free Area
(Each Opening)
Round Duct
Diameter
40,000
100 sq. In
12 inches
60,000
100 sq. In
12 inches
80,000
100 sq. In
12 inches
100,000
100 sq. In
12 inches
120,000
120 sq. In
13 inches
140,000
140 sq. In
14 inches
160,000
160 sq. In
15 inches
Example:
If the combined input rate of all appliances is less than or
equal to 100,000 Btuh, each opening must have a free
area of at least 100 square inches. If the combined input
rate of all appliances is 120,000 Btuh, each opening
must have a free area of at least 120 square inches.
Installation in a Garage
WARNING:
Do not place combustible material on or
against the furnace cabinet or within 6 inches
of the vent pipe. Do not place combustible
materials, including gasoline and any other
fl ammable vapors and liquids, in the vicinity
of the furnace.
This Gas-fi red furnace may be installed in a residential
garage with the provision that the burners and igniter
are located no less than 18 inches (457mm) above the
fl oor. The furnace must be located or protected to prevent
physical damage by vehicles.
Heating Load
The ductwork should be appropriately sized to the
capacity of the furnace to ensure its proper airfl ow rating.
For installations above 2,000 ft., the furnace should have
a sea level input rating large enough that it will meet
the heating load after deration for altitude.
Excessive
oversizing of the furnace could cause the furnace
and/or vent to fail prematurely.
COMBUSTION AIR REQUIREMENTS
Provisions must be made during the installation of
this furnace that provide an adequate supply of air for
combustion.
General Information
• Instructions for determining the adequacy of an
installation can be found in the current revision of the IFGC.
Consult local codes for special requirements
.
CAUTION:
Exhaust fans, clothes dryers, fi replaces and
other appliances that force air from the house
to the outdoors can create a negative pressure
inside the house, resulting in improper furnace
operation or unsafe conditions such as fl ame
roll out. It is imperative that suffi cient air
exchange with the outdoors is provided to
prevent depressurization.
• Air openings on top of the furnace and in closet doors
or walls must never be restricted. If the furnace is
operated without adequate air for combustion, the fl ame
roll-out switch will open, turning off the gas supply to
the burners.
This safety device is a manually reset
switch.
DO NOT reset or install jumper wires across
this switch to defeat its function without identifying
and correcting the fault condition.
If the switch must
be replaced, use only the correct sized part specifi ed
in the Replacement Parts List provided online.
Installation In A Confi ned Space
A confi ned space is an area with volume less than 50
cubic feet per 1,000 Btuh of the combined input rates of
all appliances drawing combustion air from that space.
Furnace closets, small equipment rooms and garages are
confi ned spaces. Furnaces installed in a confi ned space
which supply heated air to areas outside the space must
draw return air from outside the space and must have the
return air ducts tightly sealed to the furnace.
NOTE:
The required sizing of these openings is determined
by whether inside or outside air is used to support
combustion, the method by which the air is brought to
the space, and by the total input rate of all appliances in
the space. In all cases, the minimum dimension of any
combustion air opening is 3 inches.
Air From Inside
If combustion air is taken from the heated space, the
two openings must each have a free area of at least one
square inch per 1,000 Btuh of total input of all appliances
in the confi ned space, but
not less than
100 square
inches of free area (Figure 1). See example.
Outdoor Air from a Crawl Space or Vented Attic
When the openings can freely exchange air with the
outdoors, each opening shall have a minimum free area
of 1 square inch per 4,000 Btuh of total appliance input.
Summary of Contents for G7XA Series
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