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FURNACE
CORROSION
HAZARD
Failure to follow
this caution
may result in furnace
damage.
Air for combustion
nmst
not be contaminated
by halogen
compounds,
which
include
fluoride,
chloride,
bromide,
and
iodide.
These
elements
can corrode
heat exchangers
and
shorten
furnace
life. Air contaminants
are found
in aerosol
sprays,
detergents,
bleaches,
cleaning
solvents,
salts,
air
fresheners,
and other household
products.
CARBON
MONOXIDE
POISONING
HAZARD
Failure
to follow
this warning
could
result
in personal
injury or death.
The
operation
of exhaust
fans,
kitchen
ventilation
fans,
clothes
dryers,
attic exhaust
fans or fireplaces
could
create a
NEGATIVE
PRESSURE
CONDITION
at the
furnace.
Make-up
air MUST
be provided
for the ventilation
devices,
in addition
to that required
by the furnace.
Refer to Carbon
Monoxide
Poisoning
Hazard
warning
in venting
section
of
these
instructions
to determine
if an adequate
amount
of
make-up
air is available.
The requirements
for combustion
and ventilation
air depend
upon
whether
or not the furnace
is located
in a space having
a volume
of at least 50 cubic feet per 1,000 Btuh
input
rating
for all gas
appliances
installed
in the space.
Spaces having less than 50 cubic feet per 1,000 Btuh require the
Outdoor
Combustion
Air Method.
Spaces having at least 50 cubic feet per 1,000 Btuh may use the
Indoor
Combustion
Air, Standard
or Known
Air Infiltration
Method.
Outdoor
Combustion
Air Method
1. Provide
the space
with sufficient
air for proper
combus-
tion, ventilation,
and dilution
of flue gases using perman-
ent horizontal
or vertical
duct(s)
or opening(s)
directly
communicating
with
the
outdoors
or spaces
that freely
communicate
with the outdoors.
2. Fig.
7
illustrates
how
to
provide
TWO
OUTDOOR
OPENINGS,
one
inlet
and
one
outlet
combustion
and
ventilation
air opening,
to the outdoors.
e. One opening
MUST
commence
within
12 in. (300 ram)
of the ceiling and the second
opening
MUST
commence
within 12 in. (300 ram) of the floor.
f. Size openings
and ducts per Fig. 7 and Table 2.
g. TWO HORIZONTALDUCTS
require I -in 2 of free area
per 2,000 Btuh (1,100 mm2/kW)
of combined
input for
all gas appliances
in the space per Fig.7
and Table 2.
h. TWO OPENINGS
OR VERTICAL
DUCTS
require
1
-in 2 of free area per 4,000 Btuh (550 mm2/kW)
for com-
bined input of all gas appliances
in the space per Fig.
7
and Table 2.
3. ONE OUTDOOR
OPENING
requires:
a. One square
inch
of free area per 3,000
Btuh
(734
mm2/kW)
for combined
input of all gas appliances
in the
space per Table 2 and
b. Not less than the sum of the areas of all vent connectors
in the space.
Table 2 - Minimum
Free Area
Required
for Each Combustion
Air opening
of Duct to Outdoors
TWO HORIZONTAL
DUCTS
SINGLE DUCT OR OPENING
TWO OPENINGS
OR VERTICAL
DUCTS
FURNACE
(1 SQ. IN./2,000 BTUH) (1,100 SQ. MM/KW)
(1 SQ. IN./3,000
BTUH) (734 SQ. MM/KW)
(1 SQ. IN./4,000
BTUH) (550 SQ. MM/KW)
iNPUT
Free Area of Opening
Round Duet
Free Area of Opening
Round Duet
Free Area of Opening
Round Duet
(BTUH)
and Duet
Dia.
and Duet
Dia.
and Duet
Dia.
Sq. In. (Sq. ram)
In. (ram)
Sq. In. (Sq. ram)
In. (ram)
Sq. In. (Sq. ram)
In. (ram)
44,000
22 (14194 /
6 (152 /
14.7 (9484 /
5 (127 /
11 (7096 /
4 (102 /
66,000
33 (21290)
7 (178)
22 (14193)
6 (152)
16.5 (10645)
5 (127)
88,000
44 (28387)
8 (203)
29.3 (18903)
7 (178)
22 (14193)
6 (152)
110,000
55 (35484)
9 (229)
36.7 (23677)
7 (178)
27.5 (17742)
6 (152)
132,000
66 (42580)
10 (254)
44 (28387)
8 (203)
33 (21290)
7 (178)
154,000
77 (49677)
10 (254)
51.3 (33096)
9 (229)
38.5 (24839)
8 (203)
FURNACE
WATER HEATER
EXAMPLES: Determining Free Area
TOTAL INPUT
110,000
+
30,000
=
(140,000
divided
by 4,000)
66,000
+
40,000
=
(106,000
divided
by 3,000)
88,000
4-
30,000
=
(118,000
divided
by 2,000)
=
35.0 Sq. In. for each two Vertical Ducts or Openings
=
35.3 Sq. In. for a Single Duct or Opening
=
59.0 Sq. In. for each of two Horizontal Ducts

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