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The Standard
Method:
1. The space
has no less volume
than 50 cu/fl,
per 1,000
Btuh of the maximum
input
ratings
for all gas appliances
installed
in the space and
2. The air infiltration
rate is not known
to be less than 0.40
air changes per hour (ACH).
The Known
Air Infiltration
Rate Method
shall be used,
if the
infiltration
rate is known
to be:
1. Less than 0.40 ACH and
2. Equal to or greater
than 0.10 ACH
Infiltration
rates greater
than 0.60 ACH
shall not be used.
The
minimum
required
volume
of the space varies with the number
of
ACH and shall be deternfined
per TaMe 2 or Equations
I and 2.
Deternfine
the minimum
required
volume
for each appliance
in
the space
and add the volumes
together
to get the total minimum
required
volume
for the space.
Table
2 - Minimum
Space
Volumes
were deternfined
by using
the following
equations
from the National
Fuel Gas Code ANSI
Z223.1-2012/NFPA
54-2012,
9.3.2.2:
1. For other
than
fan-assisted
appliances,
such as a draft
hood-equipped
water heater:
Volume
-
21ft3
L_
!°ther
Other ACH H000
Btu/hr
2. For fan-assisted
appliances
such as this furnace:
Volume
_ 15ft 3 _
I fan
Fan
ACH
000 Btu/hr
A04002
A04003
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.)
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 closeaMe
doors between
rooms.
b. Combining
spaces on same floor level. Each opening
shall have free area of at least I 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 minimum
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 permanent
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.
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
Method
below.
b. Outdoor
opening
size reduction
Factor
is 1 nfinus the
Ratio
in a. above.
c. Minimum
size of Outdoor
openings
shall be the size
required
in Outdoor
Combustion
Air Method
above
nmltiplied
by reduction
Factor
in b. above.
The nfin-
imum 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
Bottom
Closure
Panel
Bottom
Filler Panel
Fig. 9 -
Removing
Bottom
Closure
Panel
A10273
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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