Instruction manual

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) D ia.
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. f or each two Vertical Ducts or Openings
60,000 + 40,000 = (100,000 divided by 3,000) = 33.3 Sq. In. f or 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-AS SISTED 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
SpaceVolumeFt
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 P ermitted
1 SQ IN.
PER
4000
BTUH*
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH*
CIRCULATING
AIR DUCTS
VENT
THROUGH
ROOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
CIRCULATING AIR DUCTS
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTDOORS
12″ MAX
12″ MAX
12″ MAX
12″
MAX
12″
MAX
OUTDOORS
1 SQ IN.
PER
4000
BTUH*
F
G
CLEARANCE IN FRONT
OF COMBUSTION AIR
OPENINGS SHALL BE
AT LEAST 3 IN.
(305mm)
(305mm)
(305mm)
(305mm)
(305mm)
(76mm)
*Minimum dimensions of 3--- in. (76 mm).
NOTE: Use any of the following combin ations of openings:
A&BC&DD&EF&G
A03174
Fig. 6 -- Air for Combustion, Ventilation, and Dilution for Outdoors
987MA