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 combustion,
ventilation, and dilution of flue gases using permanent hori-
zontal or vertical duct(s) or opening(s) directly communicat-
ing with the outdoors or spaces that freely communicate with
the outdoors.
2. Fig. 7 illustrates how to provide TWO OUTDOOR OPEN-
INGS, one inlet and one outlet combustion and ventilation air
opening, to the outdoors.
a. One opening MUST commence within 12
″
(300 mm) of
the ceiling and the second opening MUST commence
within 12
″
(300 mm) of the floor.
b. Size openings and ducts per Fig. 7 and Table 2.
c. TWO HORIZONTAL DUCTS require 1 square inch of
free area per 2,000 Btuh (1,100 mm
2
/kW) of combined
input for all gas appliances in the space per Fig. 7 and Table
2.
d. TWO OPENINGS OR VERTICAL DUCTS require 1
square inch of free area per 4,000 Btuh (550 mm
2
/kW) for
combined input of all gas appliances in the space per Fig.
7 and Table 2.
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 Btuh (734 mm
2
/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 or Duct to Outdoors
FURNACE
INPUT
(BTUH)
TWO HORIZONTAL DUCTS
(1 SQ. IN./2,000 BTUH) (1,100 SQ. MM/KW)
SINGLE DUCT OR OPENING
(1 SQ. IN./3,000 BTUH) (734 SQ. MM/KW)
TWO OPENINGS OR VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH) (550 SQ. MM/KW)
Free Area of
Opening and Duct
(Sq. In.)
Round Duct
(in. Dia)
Free Area of
Opening and Duct
(sq In.)
Round Duct
(in. Dia)
Free Area of
Opening and Duct
(Sq In.)
Round Duct
(In. Dia)
44,000
22
6
14.7
5
11
4
66,000
33
7
22
6
16.5
5
88,000
44
8
29.3
7
22
6
110,000
55
9
36.7
7
27.5
6
132,000
66
10
44
8
33
7
154,000
77
10
51.3
9
38.5
8
EXAMPLES: Determining Free Area
FURNACE
WATER HEATER
TOTAL INPUT
110,000
+
30,000
=
(140,000 divided by 4,000)
=
35.0 Sq. In. for each two Vertical Ducts or Openings
66,000
+
40,000
=
(106,000 divided by 3,000)
=
35.3 Sq. In. for a Single Duct or Opening
88,000
+
30,000
=
(118,000 divided by 2,000)
=
59.0 Sq. In. for each of two Horizontal Ducts
→
Table 3–Minimum Space Volumes for 100% Combustion, Ventilation, and
Dilution from Indoors
ACH
OTHER THAN FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
30
40
50
44
66
88
110
132
154
Space 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
8
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Summary of Contents for 58CTA
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