506303-01
Page 4 of 40 Issue 0938
Unconfined Space
An unconfined space is defined as “a space whose volume
is more than 50 cubic feet per 1000 BTU per hour of the
combined input rating of all appliances installed in that
space.” When a furnace is installed in an unconfined space
in a building, it can be assumed that the infiltration will be
sufficient to supply the required air. If the furnace is installed
in a ventilated attic or crawl space, it is assumed that the
infiltration is sufficient to supply the required air. However,
in a building of unusually tight construction, additional
outdoor air should be provided.
• The return air duct must be provided and sealed to the
furnace.
• Return air temperature range between 60°F and 80°F
must be maintained.
• Air filters must be installed in the system and must be
maintained during construction.
• Air filters must be replaced upon construction
completion.
• The input rate and temperature rise must be set per
the furnace rating plate.
• One hundred percent (100%) outdoor air must be
provided for combustion air requirements during
construction. Temporary ducting may supply outdoor
air to the furnace. Do not connect duct directly to the
furnace. Size the temporary duct following the
instructions given on this page in the Combustion and
Ventilation Air section regarding confined space with
air from outside.
• The furnace heat exchanger, components, duct system,
air filters, and evaporator coils must be thoroughly
cleaned following final construction cleanup.
• All furnace operating conditions (including ignition, input
rate, temperature rise, and venting) must be verified
according to these installation instructions.
G2D93CT and G2D95CT models installed in the horizontal
position are approved for attic installations. If the furnace
is to be installed in an attic or other insulated space, it
must be kept free and clear of insulating materials.
Clearances
All servicing and cleaning of the furnace can be performed
from the front. If installed in a closet or utility room, provide
18" clearance in front for service if the door to the room is
not in line with the front of the furnace.
Refer to Table 1 for the minimum clearances to combustibles
required for construction and proper unit operation. Where
servicing clearances are greater than clearances to
combustibles, servicing clearances take precedence.
G2D93CT and G2D95CT models may be installed on wood
flooring but shall not be installed directly on carpeting, tile, or
any other combustible material.
Combustion and Ventilation Air
Adequate provisions for combustion air and ventilation of
furnace must be made. Refer to Section 5.3, “Air for
Combustion and Ventilation,” of the National Fuel Gas Code,
ANSI Z223.1/NFPA54 (latest edition), Sections 7.2, 7.3, or
7.4 of CSA B149.1 Natural Gas and Propane Installation
Codes (latest editions), or applicable provisions of the local
building codes.
Insufficient combustion air can cause headaches, nausea,
dizziness, or asphyxiation. When considering combustion
air requirements, enough air must also be provided to
meet the needs of all fuel-burning appliances and exhaust
fans.
WARNING
Air openings in the front of the furnace must be kept free
of obstructions. Any obstruction may cause improper
operation that can result in a fire hazard or carbon
monoxide injury.
WARNING
Table 1
Minimum Clearances to
Combustibles
Upflow Horizontal
Sides
0” 0”
Rear 0” 0”
2”
18”
0”
0”
1” 1”
Front
Flue Pipe
Plenum
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