9
Alternate Method of Providing
Air from Outside:
If acceptable under local Codes, it is permitted to provide
outside air using one opening (See NFGC).
Generally,
confi ned spaces must have two openings in the space
for combustion air. One opening must be within 12
inches of the ceiling, and the other must be within 12
inches of the fl oor. However, an alternative method
recently adopted by the NFGC uses one opening within
12 inches of the top of the space. This method may be
used if it is acceptable to the local codes.
The following conditions must be met:
1. The opening must start within 12” of the top of the
structure and connect with the out of doors through
vertical or horizontal ducts or be ducted to a crawl
or attic space that connects with the out of doors.
2. The opening must have a minimum free area of 1 sq.
in. per 3,000 Btu per hour of the total input rating of
all equipment located in the enclosure.
3. The free area must not be less than the sum of all
the areas of the vent connectors in the enclosure.
Example
:
A space with a water heater rated at 45,000 Btuh
input and a furnace rated at 75,000 Btuh requires a
volume of 6,000 cubic feet [50 x (45 + 75) = 6,000] to
be considered unconfi ned. If the space has an 8 foot
ceiling, the fl oor area of the space must be 750 square
feet (6,000 / 8 = 750).
Installation In An Unconfi ned Space
An unconfi ned space is an area including all rooms not
separated by doors with a volume greater than 50 cubic
feet per 1,000 Btuh of the combined input rates of all
appliances which draw combustion air from that space.
In general, a furnace installed in an unconfi ned space will
not require outside air for combustion. However, in homes
built for energy effi ciency (low air change rates), it may
be necessary to provide outside air to ensure adequate
combustion and venting, even though the furnace is located
in an unconfi ned space. See example.
Category I Venting
This furnace is listed as a Category I vented appliance.
Category I furnaces generally operate with a slight
negative pressure (draft) and must be vented vertically or
near vertical. Additionally it is important to guard against
excessive condensation.
WARNING:
Upon completion of the furnace installation,
carefully inspect the entire fl ue system both
inside and outside the furnace to assure it is
properly sealed. Leaks in the fl ue system can
result in serious personal injury or death due
to exposure of fl ue products, including carbon
monoxide.
• This furnace must be vented in compliance with
the current revision of the National Fuel Gas Code
(ANSI-Z223.1/NFPA54) and the instructions provided
below.
Consult local codes for special requirements.
• In Canada, venting shall conform to the requirements of
the current (CAN/CGA B149.1 or .2) installation codes.
Consult local codes for special requirements.
• Category I furnace installations must be connected
to a factory built chimney or vent complying with a
recognized standard, or a masonry or concrete chimney
lined with a lining material acceptable to the authority
having jurisdiction.
WARNING:
Venting into an unlined masonry chimney or
concrete chimney is prohibited. This may result
in improper draft and excess condensation
forming in the chimney.
• This furnace may be vented with a dedicated venting
system or common vented with other Category I
appliances. The vent system dimensions and material
must conform to the NFGC or local Codes. Generally,
this means using Type B vent pipe or a lined masonry
chimney. When consulting the vent sizing tables in the
NFGC, the MAX capacity of the vent must be greater
than the furnaces high fi re rate. The MIN capacity must
be lower than the low fi re rate. If the venting system
is inappropriate for the furnace, the venting system
will need to be modifi ed to comply with NFGC or local
codes.
The minimum diameter of any vent pipe is 4
inches.
• The venting system should be designed to have the
minimum number of elbows or turns. All horizontal runs
shall slope upwards from the furnace at ¼ inch per
running foot of vent. Supports for the vent pipe must
be installed a minimum of every fi ve feet along the vent
run to ensure no displacement after installation. Under
no circumstances shall any portion of the vent system
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