18-CD19D5-10
7
Installer’s Guide
50 CU. FT. OR MORE
PER 1000 BTU/HR. INPUT
ALL EQUIP. INSTALLED
UNCONFINED
6
CONFINED
7
AIR FOR COMBUSTION AND VENTILATION
Adequate flow of combustion and ventilating air must not be
obstructed from reaching the furnace. Air openings provided in
the furnace casing must be kept free of obstructions which
restrict the flow of air. Airflow restrictions affect the efficiency
and safe operation of the furnace. Keep this in mind should you
choose to remodel or change the area which contains your
furnace. Furnaces must have a free flow of air for proper
performance.
Provisions for combustion and ventilation air shall be made in
accordance with “latest edition” of Section 5.3, Air for Combus-
tion and Ventilation, of the National Fuel Gas Code,
ANSI Z223.1, or Sections 7.2, 7.3 or 7.4 of CAN/CGA B149
Installation Codes, and applicable provisions of the local building
codes. Special conditions created by mechanical exhausting of
air and fireplaces must be considered to avoid unsatisfactory
furnace operation.
Furnace locations may be in “confined space” or “unconfined
space”. Unconfined space is defined in Table 2 and Figure 6.
These spaces may have adequate air by infiltration to provide air
for combustion, ventilation, and dilution of flue gases. Buildings
with tight construction (for example, weather stripping, heavily
insulated, caulked, vapor barrier, etc.), may need additional air
provided as described for confined space.
Confined spaces are installations with less than 50 cu. ft. of
space per 1000 BTU/hr input from all equipment installed. Air
for combustion and ventilation requirements can be supplied
from inside the building as in Figure 8 or from the outdoors, as
in Figure 9.
1. All air from inside the building as in Figure 8: The confined
space shall be provided with two permanent openings
communicating directly with an additional room(s) of
sufficient volume so that the combined volume of all spaces
meets the criteria for an unconfined space. The total input
of all gas utilization equipment installed in the combined
space shall be considered in making this determination.
Refer to Table 3, for minimum open areas required.
2. All air from outdoors as in Figure 9: The confined space
shall be provided with two permanent openings, one
commencing within 12 inches of the top and one commenc-
ing within 12 inches of the bottom of the enclosure.
The openings shall communicate directly, or by ducts, with
the outdoors or spaces (crawl or attic) that freely communi-
cate with the outdoors. Refer to Table 3, for minimum open
areas required.
LESS THAN 50 CU. FT.
PER 1000 BTU/HR. INPUT
ALL EQUIP. INSTALLED
3. The following types of installations will require use of
OUTDOOR AIR for combustion, due to chemical exposures:
* Commercial buildings
* Buildings with indoor pools
* Furnaces installed in commercial laundry rooms
* Furnaces installed in hobby or craft rooms
* Furnaces installed near chemical storage areas.
Exposure to the following substances in the combustion air
supply will also require OUTDOOR AIR for combustion:
* Permanent wave solutions
* Chlorinated waxes and cleaners
* Chlorine based swimming pool chemicals
* Water softening chemicals
* Deicing salts or chemicals
* Carbon Tetrachloride
* Halogen type refrigerants
* Cleaning solvents (such as perchloroethylene)
* Printing inks, paint removers, varnish, etc.
* Hydrochloric acid
* Cements and glues
* Antistatic fabric softeners for clothes dryers
* Masonry acid washing materials
TABLE 2
MINIMUM AREA IN SQUARE FEET
FOR UNCONFINED SPACE INSTALLATIONS
FURNACE
MAXIMUM BTUH
INPUT RATING
WITH 8 FT. CEILING
MINIMUM AREA IN SQUARE
FEET OF UNCONFINED SPACE
40,000
60,000
80,000
100,000
120,000
250
375
500
625
750
TABLE 3
MINIMUM FREE AREA IN SQUARE INCHES
EACH OPENING (FURNACE ONLY)
Furnace
Maximum
BTUH/INPUT
Rating
Air
From
Inside
Air From Outside
Vertical
Duct
Horizontal
Duct
40,000
60,000
80,000
100,000
120,000
100
100
100
100
120
10
15
20
25
30
20
30
40
50
60
Carbon monoxide, fire or smoke can cause serious bodily injury,
death, and/or property damage.
A variety of potential sources of carbon monoxide can be found in
a building or dwelling such as gas-fired clothes dryers, gas
cooking stoves, water heaters, furnaces and fireplaces. The U.S.
Consumer Product Safety Commission recommends that users of
gas-burning appliances install carbon monoxide detectors as well
as fire and smoke detectors, listed by a nationally recognized
agency (e.g. Underwriters Laboratories or International Ap-
proval Services), to help alert dwelling occupants of the presence
of fire, smoke or unsafe levels of carbon monoxide.
NOTE:
The manufacturer of your furnace does not test any detectors
and makes no representations regarding any brand or type of
detector.
