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Installation
Instructions
(cont'd)
Combustion
Air and Ventilation
for Appliances
Located
in
Unconfined
Spaces
Unconfined
Space is a space whose volume
is not less than 50
cubic feet per 1,000 Btu per hour of the aggregate input
rating
of all appliances
installed in that space. Rooms communicating
directly
with the space in which
the appliances
are installed,
through
openings
not furnished
with doors, are considered
a
part of the unconfined
space
In unconfined
spaces in buildings,
infiltration
may be adequate
to provide
air for combustion,
ventilation
and dilution
of flue
gases. However,
in buildings
of tight construction
(for example,
weather stripping,
heavily insulated,
caulked, vapor barrier, etc.),
additional
air may need
to be provided
using
the methods
described
in Combustion
Air and Ventilatiorl
for Appliances
Located in Confined
Spaces, b.
Combustion
Air and Ventilation
for Appliances Located in
Confined Spaces
Confined
Space is a space whose volume is less than 50 cubic
feet per 1,000 Btu per hour of the aggregate input rating of all
appliances installed in that space.
a. ALL AIR FROM INSIDE BUILDINGSt
(See Page 8 Figure l, and Figure 2 below)
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 com-
bined space shall be considered in making this determination.
Each opening shall have a minimum free area of one square
inch per 1,000 BTU per hour of the total input rating of all
gas utilization equipment in the confined space, but not less
than 100 square inches. One opening shall commence within
12 inches of the top and one commencing within 12 inches
of the bottom of the enclosure.
Figure
2 ]
S VENT
--3
II
I_.J
,¢_.m.i_-,
b. ALL AIR FROM
OUTDOORS:
(see Figures 3-5)
The confined
space shall be provided
with two permanent
openings,
one commencing
within
12 inches of the top and
one commencing
within
12 inches from the bottom
of the
enclosure.
The openings
shall communicate
directly,
or by
ducts, with the outdoors
or spaces (crawl or attic) that freely
communicate
with the outdoors.
Figure 3 ]
CHIMNEy O_ GAS VENT
VE_TIt_T_
LOUVERS
(_ar_
end e{ attic)
AIR OUTLET
WATER HEATER
FURN,'_3E
_IR
DOCT
ALT INLETAIR
VENTILATIONLO4JVERS
1. When directly communicating
with the outdoors,
each open-
ing shall have a minimum
free area of 1 square inch per 4,000
BTU per hour of total input
rating of all equipment
in the
enclosure. (See Figure 3.)
2. When
communicating
with
the outdoors
through
vertical
ducts,
each opening
shall have a minimum
free area of 1
square inch per 4,000 BTU per hour of total input rating of
all equipment
in the enclosure.
(See Figure 4.)
Figure 4 ]
_CHIMNEY
OR GAS VENT
VENTILATION
LOUVERS
(each end
of attic)
LET
WATER
HEATER
FURNACE
INLET
AIR DUCT
above tloor }
10
3. When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of 1
square inch per 2,000 BTU per hour of total input rating of
all equipment in the enclosure. (See Figure 5.)
Figure 5 ]
_
CHIMNEY
OR GAS VENT
i_
OUTLET
AJR DUCT
WATER
HEATER
FURNACE
--
INLET AIR DUCT
,
When ducts are used, they shall be of the same cross-sectional
area as the free area of the openings
to which they connect.
The minimum
short side dimension
of rectangular
air ducts
shall not be less than 3 inches. (See Figure 5.)
,
Louvers
and Grilles:
In calculating
free area, consideration
shall be given to the blocking
effect of louvers,
grilles
or
screens protecting
openings.
Screens used shall not be smaller
than ¼ inch mesh. If the free area through
a design of louver
or grille is known,
it should
be used in calculating
the size
opening
required
to provide
the free area specified.
If the
design and free area is not known,
it may he assumed
that
wood louvers will be 20-25 percent free area and metal louvers
and grilles will have 60-75
percent
free area. Louvers
and
grilles shall be fixed in the open position or interlocked
with
the equipment
so that they are opened
automatically
during
equipment
operation.
6. Special Conditions
Created by Mechanical Exhausting or
Fireplaces: Operation of exhaust fans, ventilation systems,
clothes dryers or fireplaces may create conditions requirin_
special attention to avoid unsatisfactory operation of insta[leci
gas utilization equipment.
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