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3.6 Combustion Air and Ventilation
Important: All aspects of the installation of this
boiler, including materials, methods of providing
combustion air and methods of venting products of
combustion to the outdoors must comply with all
local codes and the following national standards:
1) CSA B149.1 (most recent edition) - Natural Gas
and Propane Installation Code (Canada)
2) NFPA 54 (most recent edition) - National Fuel Gas
Code (US)
3) NFPA 58 (most recent edition) - Liquefi ed Petro-
leum Gas Code (US)
Adequate fl ow of combustion and ventilating air
must not be obstructed from reaching the boiler.
Air openings provided in the boiler casing must be
kept free of obstructions which restrict the fl ow of
air. Airfl ow restrictions affect the effi ciency and safe
operation of the boiler. Keep this in mind should you
choose to remodel or change the area which contains
your boiler. Boilers must have a free fl ow of air for
proper performance.
Provisions for combustion and ventilation air shall
be made in accordance with "latest edition" of Sec-
tion 5.3, Air for Combustion 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 exhaust air
and fi replaces must be considered to avoid unsatis-
factory boiler operation.
Boiler locations may be in "unconfi ned space" or
"confi ned space". Unconfi ned space is defi ned in
Table 4 and Figure 10.
Fig. 10
UNCONFINED
50 CU. FT. OR MORE
PER 1000 BTU/HR. INPUT
ALL EQUIP. INSTALLED
These spaces must have adequate air by infi ltration
to provide air for combustion, ventilation, and dilu-
tion of fl ue gases. Buildings with tight construction
(for example, weather stripping, heavily insulated,
caulked, vapor barrier, etc.), may need additional air
provided as described for confi ned space.
Confi ned spaces are installations with less than 50
cu. ft. of space per 1000 BTU/hr input from all equip-
ment installed as in Figure 11.
CONFINED
Fig. 11
LESS THAN 50 CU. FT.
PER 1000 BTU/HR. INPUT
ALL EQUIP INSTALLED
18-CG01D1-4
18
Minimum Area in Square Feet for Unconfi ned
Space Installations
Boiler Maximum
BTUH / Input Rating
90,000
130,000
173,000
215,000
TABLE 5
Minimum Free Area in Square Inches Each
Opening (Boiler Only)
Boiler
Air From
Maximum
Inside
BTUH /
Input Rating
90,000
100
130,000
130
173,000
175
215,000
215
Air for combustion and ventilation requirements can
be supplied from inside the building as in Figure 12
or from the outdoors, as in Figure 13 (see page 19).
1. All air from inside the building as in Figure 12:
The confi ned space shall be provided with two
permanent openings communicating directly
with an additional room(s) of suffi cient volume so
that the combined volume of all spaces meets the
criteria for an unconfi ned space. The total input
of all gas utilization equipment installed in the
combined space shall be considered in making
this determination. Refer to Table 4, for mini-
mum open areas required.
2. All air from outdoors as in Figure 13: The con-
fi ned space shall be provided with two permanent
openings, one commencing within 12 inches of
the top and one commencing within 12 inches of
the bottom of the enclosure. The openings shall
communicate directly, or by ducts, with the out-
doors or spaces (crawl or attic) that freely com-
municate with the outdoors. Refer to Table 5, for
minimum open areas required.
TABLE 4
With 8 Foot Ceiling
Minimum Area in Square
Feet of Unconfi ned
Space
560
810
1080
1340
Air From Outside
Vertical
Horizon-
Duct
tal Duct
25
35
45
55
50
70
90
110
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