American Standard PFWF071A93ABA Installation Manual page 19

installation codes always take precedence and shall
be followed.
The content of certain pertinent passages of NFPA
31, (most recent edition) methods to obtain and
ensure adequate combustion airfl ow to the boiler
has been excerpted and, in some cases, paraphrased
below for reference purposes. Consult the Standard
for the Installation of Oil-Burning Equipment, NFPA
31- (most recent edition) and Installation Code for Oil
Burning Equipment (Canada) CSA B139 (most recent
edition), for special cases and further details.
Boiler locations may be in "confi ned space" or "uncon-
fi ned space." However, if the boiler is installed in a
"confi ned space," combustion air must be provided by
a means conforming to local or national codes. some
example methods are described herein.
Confi ned Space
Confi ned spaces, as shown in Figure 8, are installa-
tions with less than 50 cubic feet of space per 1000
BTU/hr input from all appliances installed in the
space. Air for combustion and ventilation require-
ments can be supplied from inside the buildings in
fi gure 9 or from the outdoors as in Figure 10.
Utility Room (example of a confi ned space):
a. In buildings of conventional construction with
normal air infi ltration, two (2) permanent openings
connecting to a well-ventilated crawl space, attic, or
another large, well-ventilated internal area shall be
provided. Each opening shall have a minimum free
area of one (1) square inch per 1000 BTUH of total
input rate (sum of the individual appliance input
rates) of all appliances to be installed in the utility
room. One opening should be located near, or in, the
ceiling of the room and the other should be located
near, or in, the fl oor.
b. In buildings of unusually tight construction
(e.g. those having continuous water vapor barriers;
tightly-fi tting, or weather-stripped, doors and win-
dows; and gasketed, caulked, or sealed outer wall
joints and penetrations), wherein infi ltration and air
exchange with the outdoors is very limited (0.35 air
changes per hour, or less), provision must be made to
provide suffi cient air for combustion. The following
method will usually be adequate to ensure suffi cient
airfl ow into the space:
Provide two (2) permanent openings, one (1) located
within 12 inches of the fl oor and one (1) within 12
inches of the ceiling, or roof, of the room. These
openings shall allow for direct exchange of air
between the room and outdoors. If required, duc-
ting between the room and the outdoors shall be
provided.
- For horizontally -oriented ducts, each opening shall
have a minimum free area of one (1) square inch
per 2000 BTUH of the total input rate (sum of the
UNCONFINED
SPACE
50 CU. FT. OR MORE
PER 1000 BTU/HR. INPUT
ALL EQUIP. INSTALLED
Boiler Maximum
BTUH Input Rating
80,000
100,000
140,000
170,000
180,000
210,000
250,000
290,000
individual appliance input rates) of all appliances
to be installed in the room.
- For vertically -oriented ducts, the minimum free
area may be reduced to one (1) square inch per
4000 BTUH of the total input rate (sum of the
individual appliance input rates) of all appliances
to be installed in the room.
- The minimum dimension of any air opening shall
not be less than 3-inches.
- When an opening in the outside wall must be provi-
ded, it should be furnished with properly screened
metal sleeves.
Unconfi ned Space
Unconfi ned spaces are defi ned in Figure 11 and Table
4. These spaces may have adequate air to provide
for combustion, ventilation, and dilution of fl ue gases
from infi ltration. Buildings with tight construction
(for example, weather stripping, heavy insulated,
caulked, with vapor barrier, etc. may need additio-
nal air provided as described for confi ned space. An
unconfi ned space is any space where the volume is
equal to or greater than 50 cubic foot per 1000 BTU/
hr or the aggregate input rating of all appliances
installed therein.
Figure 11
Table 4
With 8 Ft. Ceiling Mini-
mum Area in Square Feet
of Unconfi ned Space
500
625
875
1,063
1,125
1,313
1,563
1,813
18-CG03D1-4
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