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58SC0B/58SC1B: Installation, Start–Up, Operating and Service and Maintenance Instructions
The opening shall commence within 12" (300 mm) of the ceiling.
Appliances in the space shall have clearances of at least 1" (25 mm)
from the sides and back and 6" (150 mm) from the front. The opening
shall directly communicate with the outdoors or shall communicate
through a vertical or horizontal duct to the outdoors or spaces (crawl or
attic) that freely communicate with the outdoors.
Indoor Combustion Air - NFPA & AGA
Standard and Known-Air-Infiltration Rate Methods
Indoor air is permitted for combustion, ventilation, and dilution, if the
Standard or Known-Air-Infiltration Method is used.
Table 2 – Minimum Free Area Required for Each Combustion Air Opening or Duct to Outdoors
TWO HORIZONTAL DUCTS
(1 SQ. IN./2,000 BTUH)
FURNACE
INPUT (BTUH)
Free Area of
Opening and Duct
(sq. in. / sq. mm)
44,000
22 (14193)
66,000
33 (21290)
88,000
44 (28387)
110,000
55 (35484)
132,000
66 (42581)
154,000
77 (49677)
FURNACE
WATER HEATER
110,000
+
66,000
+
88,000
+
The Standard Method
Use the Standard Method if:
1. The space has no less volume than 50 cubic feet 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).
Use the Known Air Infiltration Rate Method 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 determined per
Table 3
or Equations 1 and 2. Determine 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 3
- Minimum Space Volumes were determined by using the
following equations from the current edition of National Fuel Gas Code
ANSI Z223.1/NFPA 54:
1. For other than fan-assisted appliances, such as a draft
hood-equipped water heater:
2. For fan-assisted appliances such as this furnace:
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
(1,100 SQ. MM/KW)
Round Duct
Diameter
(in./mm)
6 (152)
7 (178)
8 (203)
9 (229)
10 (254)
10 (254)
EXAMPLES: Determining Free Area
30,000
=
(140,000 divided by 4,000)
40,000
=
(106,000 divided by 3,000)
30,000
=
(118,000 divided by 2,000)
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in death and/or personal
injury.
Many homes require air to be supplied from outdoors for furnace
combustion, ventilation, and dilution of flue gases. The furnace
combustion air supply must be provided in accordance with this
instruction manual.
SINGLE DUCT OR OPENING
(1 SQ. IN./3,000 BTUH)
(734 SQ. MM/KW)
Free Area of
Round Duct
Opening and Duct
Diameter
(sq. In. / sq. mm)
(in. / mm)
14.7 (9484)
5 (127)
22 (14193)
6 (152)
29.3 (18903)
7 (178)
36.7 (23677)
7 (178)
44 (28387)
8 (203)
51.3 (33096)
9 (229)
TOTAL INPUT
=
=
=
If the following is applied to either equation:
I
•
other = combined input of all other than fan-assisted appliances in
BTUh/hr
I
•
fan = 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 closeable doors between rooms.
b. Combining spaces on same floor level. Each opening shall have
free area of at least 1 in.
total input rating of all gas appliances in the space, but not less
than 100 in.
(300 mm) of the ceiling and the second opening shall commence
within 12" (300 mm) of the floor. The minimum dimension of air
openings shall be at least 3 in. (80 mm) (see
c. Combining space on different floor levels. The volumes of
spaces on different floor levels shall be considered as
communicating spaces if connected by one or more permanent
openings in doors or floors having free area of at least 2
2
in.
/1,000 BTUh (4,400 mm
appliances.
A04002
A04003
8
WARNING
!
TWO OPENINGS OR VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH)
(550 SQ. MM/KW)
Free Area of
Opening and Duct
(sq. In. / sq. mm)
11 (7097)
16.5 (10645)
22 (14193)
27.5 (17742)
33 (21290)
38.5 (24839)
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
2
/1,000 BTUh (2,000 mm
2
2
(0.06 m
). One opening shall commence within 12"
2
/kW) of total input rating of all gas
Round Duct
Diameter
(In./mm)
4 (102)
5 (127)
6 (152)
6 (152)
7 (178)
8 (203)
2
/kW) of the
Fig.
8).
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