6
18-IN. (457.2 mm)
MINIMUM TO BURNERS
A93044
Fig. 5 -- Installation in a Garage
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.
!
WARNING
PERSONAL
INJURY
AND/OR
PROPERTY
DAMAGE
Improper use or installation of this furnace may cause
premature furnace component failure.
This furnace is not permitted to be used for heating of
buildings under construction.
CAUTION
!
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 Open-
ing and Duct
Sq. In (Sq. mm)
Round Duct
In. (mm)
Dia
Free Area of Open-
ing and Duct
Sq. In (Sq. mm)
Round
Duct
In. (mm)
Dia
Free Area of Opening
and Duct
Sq. In (mm)
Round Duct
In. (mm) Dia.
40,000
20 (12904)
5 (127)
14 (8696)
5 (127)
10 (6452)
4 (102)
60,000
30 (19355)
6 (152)
20 (13043)
5 (127)
15 (9678)
5 (127)
80,000
40 (25807)
7 (178)
27 (17391)
6 (152)
20 (12904)
5 (127)
100,000
50 (32258)
8 (203)
34 (21739)
7 (178)
25 (16130)
6 (152)
* Not all input sizes are available.
EXAMPLE
:
Determining Free Area
FURNACE
WATER HEATER
TOTAL INPUT
100,000
+
30,000
= (130,000 divided by 4,000)
= 32.5 Sq. In. for each two Vertical Ducts or
Openings
60,000
+
40,000
= (100,000 divided by 3,000)
= 33.3 Sq. In. for each Single Duct or Opening
80,000
+
30,000
= (110,000 divided by 2,000)
= 55.0 Sq. In. for each 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
Space Volume (ft.
3
)
0.60
1,050
1,400
1,750
1,100
1,650
2,200
2,750
3,300
0.50
1,260
1,680
2,100
1,320
1,980
2,640
3,300
3,960
0.40
1,575
2,100
2,625
1,650
2,475
3,300
4,125
4,950
0.30
2,100
2,800
3,500
2,200
3,300
4,400
5,500
6,600
0.20
3,150
4,200
5,250
3,300
4,950
6,600
8,250
9,900
0.10
6,300
8,400
10,500
6,600
9,900
13,200
16,500
19,800
0.00
NP
NP
NP
NP
NP
NP
NP
NP
*Air Changes/Hour
