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ALL FURNACE INSTALLATIONS MUST COMPLY WITH
THE NATIONAL FUEL GAS CODE, NFPA 54, AND IN
CANADA CSA B149.1; CANADIAN NATURAL GAS AND
PROPANE INSTALLATION CODE, THE NATIONAL FIRE
CODE OF CANADA, AND LOCAL CODES TO PROVIDE
ADEQUATE COMBUSTION AND VENTILATION AIR FOR
THE FURNACE. FAILURE TO DO SO CAN RESULT IN EX-
PLOSION, FIRE, PROPERTY DAMAGE, CARBON MONOX-
IDE POISONING, PERSONAL INJURY OR DEATH.
For improved indoor air quality, added safety and product per-
formance we recommend direct vent type installations. If non-di-
rect type vent system is used, the requirements for combustion
air must be provided as identified in the National Fuel Gas Code
and, in Canada, CSA B149.1; Canadian Natural Gas and
Propane Installation Code.
Combustion air requirements are determined by whether the fur-
nace is in an open (unconfined) area or in a confined space such
as a closet or small room.
CONFINED AND UNCONFINED
SPACES
The below instructions are for U.S. installations only. The terms
Confined Space and Unconfined Space refer to U.S. installa-
tions only. In Canada the proper term to use is Enclosure when
specifying that a furnace is installed in a partially enclosed or fully
enclosed room or space. For Canadian installations, to determine
combustion air requirements for non-direct vent installations, the
installer must follow CSA B149.1; Canadian Natural Gas and
Propane Installation Code and NOT the below instructions.
FURNACE LOCATED IN AN UNCON-
FINED SPACE (U.S. INSTALLATIONS)
USING INDOOR AIR FOR COMBUSTION:
An unconfined space must have at least 50 cubic feet for each
1,000 BTUH of total input for all appliances in the space. Table 7
below specifies minimum space requirements and a few exam-
ples of the room sizes required for different inputs. The sizes are
based on 8-foot ceilings.
If the open space containing the furnace is in a building with tight
construction, outside air may still be required for the furnace to
operate and vent properly. Outside air openings should be sized
the same as for a confined space.
52
TABLE 7: MINIMUM SPACE REQUIREMENTS
!%
FOR UNCONFINED SPACE, NON-DIRECT VENT
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FURNACE LOCATED IN A CONFINED
SPACE (U.S. INSTALLATIONS)
A confined space is defined as any space for a given furnace input
rating which is smaller than that which is specified in Table 7 as
minimum for an "unconfined" space. If the space is less than that
specified in this table, the space is defined as "confined".
If the space is small enough to be designated as "confined", it
must have openings into the space which are located in accor-
dance with the requirements set forth in the following subsections
A and B. Size connected to the heated area or to the outside, and
by the input of ALL appliances in the space.
If the confined space is within a building with tight construction,
combustion air must be taken from outdoors or from an area
freely communicating with the outdoors.
A. USING INDOOR AIR FOR COMBUSTION:
IMPORTANT: Air should not be taken from a heated space
with a fireplace, exhaust fan or other device that may pro-
duce negative pressure.
If combustion air is taken from the heated area, the openings
must each have at least 100 square inches of free area.
Each opening must have at least one square inch of free
area for each 1,000 BTUH of total input in the space. Table 8
shows some typical examples of openings required for com-
bustion air openings required for a confined space.
%
%
TABLE 8: MINIMUM FREE AREA
OPENING REQUIRED FOR A
$
FURNACE LOCATED IN A
$
CONFINED SPACE USING
$
INDOOR AIR FOR COMBUSTION.
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