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Table
3 - Minimum
Space Volumes
for 100 % Combustion,
Ventilation,
and Dilution
from Indoors
OTHER
THAN
FAN-ASSISTED
TOTAL
FAN-ASSISTED
TOTAL
(1,000s
BTUH
GAS
INPUT
RATE)
(1,000s
BTUH
GAS
INPUT
RATE)
ACH
30
40
50
44
66
88
110
132
154
S _ace Volume
(ft.3)
0.60
1,050
1,400
1,750
1,100
1,650
2,200
2,750
3,300
3,850
0.50
1,260
1,680
2,100
1,320
1,980
2,640
3,300
3,960
4,620
0.40
1,575
2,100
2,625
1,650
2,475
3,300
4,125
4,950
5,775
0.30
2,100
2,800
3,500
2,200
3,300
4,400
5,500
6,600
7,700
0.20
3,150
4,200
5,250
3,300
4,950
6,600
8,250
9,900
11,550
0.10
6,300
8,400
10,500
6,600
9,900
13,200
16,500
19,800
23,100
0.00
NP
NP
NP
NP
NP
NP
NP
NP
NP
NP = Not Permitted
Table 3-Minimum
Space
Volumes
were
determined
by using
the following
equations
from the National
Fuel Gas Code ANSI
Z223.1-2009/NFPA
54-2009,
9.3.2.2:
1. For other
than
fan-assisted
appliances,
such as a draft
hood-equipped
water heater:
Volume
- 21ft3 _
I °ther
Other ACH
000 Btu/hr
2. For fan-assisted
appliances
such as this furnace:
A04002
A04003
Volume
_ 15ft 3 _
I fan
Fan
ACH
000 Btu/hr
If:
Iother
=
combined
input of all other than fan-assisted
appliances
in Btuh/hr
Ifan
=
combined
input of all fan-assisted
appliances
in
Btuh/hr
ACH
=
air changes
per hour (ACH
shall not exceed 0.60.)
However, in buildings with unusually tight construction,
additional air MUST be provided using the methods de-
scribed in the Outdoor Combustion Air Method section.
Unusually tight construction
is defined as Construction
with:
a. Walls and ceilings exposed to the outdoors have a con-
tinuous, sealed vapor barrier. Openings are gasketed or
sealed and
b. Doors and openable windows are weatherstripped
and
c. Other openings are caulked or sealed. These include
joints around window and door frames, between sole
plates and floors, between wall-ceiling joints, between
wall panels, at penetrations for plumbing, electrical and
gas lines, etc.
Combination
of Indoor and Outdoor Air
1. Indoor openings shall comply with the Indoor Combus-
tion Air Method below and,
2. Outdoor openings shall be located as required in the Out-
door Combustion
Air Method mentioned previously and,
3. Outdoor openings shall be sized as follows:
a. Calculate the Ratio of all Indoor Space volume divided
by required volume for Indoor Combustion
Air Meth-
od below.
The following
requirements
apply
to the Standard
Method
and
to the Known
Air Infiltration
Rate Method.
1. Adjoining
rooms
can be considered
part of a space if:
a. There are no closeable
doors between
rooms.
b. Combining
spaces
on same floor
level.
Each opening
shall have free area of at least 1 in.2/1,000
Btuh (2,000
mm2/kW)
of the total input rating
of all gas appliances
in the space,
but not less than 100 in. 2 (0.06 m2). One
opening
shall commence
within
12 in. (300 ram) of the
ceiling
and the second
opening
shall commence
within
12 in. (300 ram) of the floor. The nfininmm
dimension
of air openings
shall be at least 3 in. (80 ram). (See Fig.
8.)
c. Combining
space on different
floor levels. The volumes
of spaces
on different
floor levels shall be considered
as
conmmnicating
spaces if connected
by one or more per-
manent
openings
in doors
or floors
having
free area of
at least 2 in.2/1,000
Btuh (4,400 mm2/kW)
of total input
rating of all gas appliances.
2. An
attic or crawlspace
may be considered
a space
that
freely conmmnicates
with the outdoors
provided
there are
adequate
permanent
ventilation
openings
directly
to out-
doors
having
free area of at least
1-in.2/4,000
Btuh
of
total input rating for all gas appliances
in the space.
3. In spaces that use the Indoor
Combustion
Air Method,
in-
filtration
should
be adequate
to provide
air for combus-
tion,
permanent
ventilation
and
dilution
of flue
gases.
b.
c.
Outdoor
opening
size reduction
Factor
is 1 nfinus
the
Ratio
in a. above.
Mininmm
size of Outdoor
openings
shall be the size re-
quired in Outdoor
Combustion
Air Method
above nml-
tiplied by reduction
Factor
in b. above.
The minimum
dimension
of air openings
shall be not less than 3 in. (80
mm).
INSTALLATION
UPFLOW
INSTALLATION
Bottom
Return
Air Inlet
These furnaces
are shipped
with bottom
closure
panel installed
in
bottom
return-air
opening.
Remove
and discard
this panel when
bottom
return
air is used.
To remove
bottom
closure
panel,
perform
the following:
1. Tilt or raise furnace
and remove
2 screws
holding
bottom
filler panel. (See Fig. 90
2. Rotate
bottom
filler panel
downward
to release
holding
tabs.
3. Remove
bottom
closure
panel.
4. Reinstall
bottom
filler panel and screws.
Side Return
Air Inlet
These furnaces
are shipped
with bottom
closure
panel installed
in
bottom
return-air
opening.
This panel
MUST
be in place when
only side return air is used.
10

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