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Fig. 5 - - Installation in a Garage
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
Free Area of Open-
INPUT
ing and Duct
(BTUH)
Sq. In (Sq. mm)
40,000
20 (12904)
60,000
30 (19355)
80,000
40 (25807)
100,000
50 (32258)
EXAMPLE: Determining Free Area
FURNACE
WATER HEATER
100,000
+
30,000
60,000
+
40,000
80,000
+
30,000
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
ACH*
30
0.60
1,050
0.50
1,260
0.40
1,575
0.30
2,100
0.20
3,150
0.10
6,300
0.00
NP
*Air Changes/Hour
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death and/or property damage.
Do not install the furnace on its back or hang furnace with
control compartment facing downward. Safety control
operation will be adversely affected. Never connect
return- -air ducts to the back of the furnace. (See Fig. 6)
18-IN. (457.2 mm)
MINIMUM TO BURNERS
(1,100 SQ. MM/KW)
Round Duct
In. (mm)
Dia
5 (127)
6 (152)
7 (178)
8 (203)
TOTAL INPUT
=
(130,000 divided by 4,000)
=
(100,000 divided by 3,000)
=
(110,000 divided by 2,000)
40
50
1,400
1,750
1,680
2,100
2,100
2,625
2,800
3,500
4,200
5,250
8,400
10,500
NP
NP
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
When the furnace is installed in a residential garage, the
burners and ignition sources must be located at least 18
inches above the floor. (See Fig. 5) The furnace must be
located or protected to avoid damage by vehicles. When the
furnace is installed in a public garage, airplane hangar, or
other building having a hazardous atmosphere, the furnace
must be installed in accordance with the NFGC.
A93044
SINGLE DUCT OR OPENING
(1 SQ. IN./3,000 BTUH)
(734 SQ. MM/KW)
Round
Duct
Free Area of Open-
ing and Duct
In. (mm)
Sq. In (Sq. mm)
14 (8696)
5 (127)
20 (13043)
5 (127)
27 (17391)
6 (152)
34 (21739)
7 (178)
32.5 Sq. In. for each two Vertical Ducts or
=
Openings
= 33.3 Sq. In. for each Single Duct or Opening
= 55.0 Sq. In. for each two Horizontal Ducts
(1,000'S BTUH GAS INPUT RATE)
40
3
Space Volume (ft.
)
1,000
1,200
1,500
2,000
3,000
6,000
NP
Fig. 6 - - Prohibit Installation on Back
6
WARNING
TWO OPENINGS OR
VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH)
(550 SQ. MM/KW)
Free Area of Opening
and Duct
Dia
Sq. In (mm)
10 (6452)
15 (9678)
20 (12904)
25 (16130)
FAN---ASSISTED TOTAL
60
80
1,500
2,000
1,800
2,400
2,250
3,000
3,000
4,000
4,500
6,000
9,000
12,000
NP
NP
Round Duct
In. (mm) Dia.
4 (102)
5 (127)
5 (127)
6 (152)
100
3,300
3,960
4,950
6,600
9,900
19,800
NP
A02054
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