58TN0B/58TN1B: Installation, Start–Up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
8
.
NP = Not Permitted
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 National Fuel Gas Code ANSI
Z223.1/NFPA 54, 9.3.2.2:
1. For other than fan-assisted appliances, such as a draft
hood-equipped water heater, use the following equation:
A04002
2. For fan-assisted appliances such as this furnace, use the following
equation:
A04003
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.)
Then the following requirements apply to both 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 mm
2
/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 mm) of the ceiling and the second opening shall
commence within 12 in. (300 mm) of the floor. The minimum
dimension of air openings shall be at least 3 in. (80 mm), see
Fig. 8.
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
in.
2
/1,000 BTUh (4,400 mm
2
/kW) of total input rating of all gas
appliances
2. An attic or crawlspace may be considered a space that freely
communicates with the outdoors provided there are adequate
permanent ventilation openings directly to outdoors 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, infiltration
should be adequate to provide air for combustion, permanent
ventilation and dilution of flue gases. However, in buildings with
unusually tight construction, additional air MUST be provided
using the methods described in the Outdoor Combustion Air
Method section.
4. Unusually tight construction is defined as Construction with:
a. Walls and ceilings exposed to the outdoors have a continuous,
sealed vapor barrier. Openings are gasketed or sealed and
b. Doors and openable windows are weatherstripped and
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
OTHER THAN FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
ACH
30 40 50 44 66 88 110 132 154
Space Volume Ft
3
(M
3
)
0.60
1,050
(29.7)
1,400
(39.6)
1,750
(49.5)
1,100
(31.1)
1,650
(46.7)
2,200
(62.2)
2,750
(77.8)
3,300
(93.4)
3,850
(109.0)
0.50
1,260
(35.6)
1,680
(47.5)
2,100
(59.4)
1,320
(37.3)
1,980
(56.0)
2,640
(74.7)
3,300
(93.4)
3,960
(112.1)
4,620
(130.8)
0.40
1,575
(44.5)
2,100
(59.4)
2,625
(74.3)
1,650
(46.7)
2,475
(70.0)
3,300
(93.4)
4,125
(116.8)
4,950
(140.1)
5,775
(163.5)
0.30
2,100
(59.4)
2,800
(79.2)
3,500
(99.1)
2,200
(62.2)
3,300
(93.4)
4,400
(124.5)
5,500
(155.7)
6,600
(186.8)
7,700
(218.0)
0.20
3,150
(89.1)
4,200
(118.9)
5,250
(148.6)
3,300
(93.4)
4,950
(140.1)
6,600
(186.8)
8,250
(233.6)
9,900
(280.3)
11,550
(327.0)
0.10
6,300
(178.3)
8,400
(237.8)
10,500
(297.3)
6,600
(186.8)
9,900
(280.3)
13,200
(373.7)
16,500
(467.2)
19,800
(560.6)
23,100
(654.1)
0.00 NP NP NP NP NP NP NP NP NP
Volume
Other
=
21ft
3
ACH
I
other
1000 Btu/hr
Volume
Fan
=
15ft
3
ACH
I
fan
1000 Btu/hr
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