10
Table 3 – 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 (Sq. mm)
Round Duct
In. (mm) Dia
Free Area of
Opening and Duct
Sq. In (Sq. mm)
Round Duct
In. (mm) Dia
Free Area of Open-
ing 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)
120,000
60 (38709)
9 (229)
40 (26087)
7 (178)
30 (19355)
6 (152)
140,000*
70 (45161)
10 (254)
47 (30435)
8 (203)
35 (22581)
7 (178)
*
Not all families have these models.
EXAMPLES: 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 4 – Minimum Space Volumes for 100% Combustion, Ventilation and Dilution Air from Outdoors
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
40
60
80
100
120
140
Space Volume Ft
3
(M
3
)
0.60
1,050
(29.7)
1,400
(39.6)
1,750
(49.5)
1,400
(39.6)
1,500
(42.5)
2,000
(56.6)
2,500
(70.8)
3,000
(84.9)
3,500
(99.1)
0.50
1,260
(35.6)
1,680
(47.5)
2,100
(59.4)
1,680
(47.5)
1,800
(51.0)
2,400
(67.9)
3,000
(84.9)
3,600
(101.9)
4,200
(118.9)
0.40
1,575
(44.5)
2,100
(59.4)
2,625
(74.3)
2,100
(59.4)
2,250
(63.7)
3,000
(84.9)
3,750
(106.1)
4,500
(127.3)
5,250
(148.6)
0.30
2,100
(59.4)
2,800
(79.2)
3,500
(99.1)
2,800
(79.2)
3,000
(84.9)
4,000
(113.2)
5,000
(141.5)
6,000
(169.8)
7,000
(198.1)
0.20
3,150
(89.1)
4,200
(118.9)
5,250
(148.6)
4,200
(118.9)
4,500
(127.3)
6,000
(169.8)
7,500
(212.2)
9,000
(254.6)
10,500
(297.1)
0.10
6,300
(178.0)
8,400
(237.8)
10,500
(297.3)
8,400
(237.8)
9,000
(254.6)
12,000
(339.5)
15,000
(424.4)
18,000
(509.2)
21,000
(594.1)
0.00
NP
NP
NP
NP
NP
NP
NP
NP
NP
NP = Not Permitted
CONDENSATE TRAP
Condensate Trap--Upflow Orientation
When the furnace is installed in the upflow position, it is not
necessary to relocate the condensate trap or associated tubing.
Refer to Fig. 8 for upflow condensate trap information. Refer to
Condensate Drain section for information how to install the
condensate drain.
Condensate Trap--Downflow Orientation
When the furnace is installed in the downflow position, the
condensate trap will be initially located at the upper left corner of
the collector box, as received from the factory. See the top image
in Fig. 9. When the furnace is installed in the downflow
orientation, the condensate trap must be relocated for proper
condensate drainage. See the bottom image in Fig. 9.
To Relocate the Condensate Trap:
S
Orient the furnace in the downflow position.
S
Fig. 9 shows the condensate trap and tubing before and after
relocation. Refer to Fig. 9 To begin the trap conversion.
S
Refer to Condensate Drain section for information how to
install the condensate drain.
Remove knockout.
Install grommet before
relocating condensate
trap.
NOTE: Trap grommet is required only for direct-vent
applications.
A11582
Fig. 7 -- Horizontal Drain Trap Grommet
Condensate Trap--Horizontal Orientation
When the furnace is installed in the horizontal right position, the
condensate trap will be initially located at the bottom left corner of
the collector box, as received from the factory. See the top image
in Fig. 10. When the furnace is installed in the horizontal left
position, the condensate trap will be initially located at the top of
the collector box, as received from the factory. See the top image
in Fig. 11. In both cases, the trap must be repositioned on the