Minimum Free Area Required; Minimum Space Volumes - International comfort products A Series Installation Instructions Manual

municating spaces if connected by one or more permanent
openings in doors or floors having free area of at least 2
2
in. /1,000 Btuh (4,400 mm
all gas appliances.
2. An attic or crawlspace may be considered a space that freely
communicates with the outdoors provided there are ad-
equate permanent ventilation openings directly to outdoors
having free area of at least 1- -in.
rating for all gas appliances in the space.
3. In spaces that use the Indoor Combustion Air Method, in-
filtration 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 continu-
ous, sealed vapor barrier. Openings are gasketed or sealed
and
b. Doors and openable windows are weatherstripped and
Table 3 – Minimum Free Area Required for Each Combustion Air Opening or Duct to Outdoors
TWO HORIZONTAL DUCTS
(1 SQ. IN./2,000 BTUH)
(1,100 SQ. MM/KW)
FURNACE
INPUT
Free Area of
(BTUH)
Opening and
Duct
Sq. In (Sq. mm)
60,000 30 (19355)
80,000 40 (25807)
100,000 50 (32258)
FURNACE WATER HEATER
60,000 + 40,000
80,000 + 30,000
100,000 + 30,000
Table 4 – Minimum Space Volumes for 100% Combustion, Ventilation and Dilution Air from Outdoors
OTHER THAN FAN-ASSISTED
TOTAL
AIR
(1,000'S BTUH GAS INPUT
CHANGES
PER
RATE)
HOUR
30 40
(ACH)
1,050 1,400
0.60
(29.7) (39.6)
1,260 1,680
0.50
(35.6) (47.5)
1,575 2,100
0.40
(44.5) (59.4)
2,100 2,800
0.30
(59.4) (79.2)
3,150 4,200
0.20
(89.1) (118.9)
6,300 8,400
0.10
(178.0) (237.8)
0.00 NP NP
NP = Not Permitted
10
2
/kW) of total input rating of
2
/4,000 Btuh of total input
SINGLE DUCT OR OPENING
Free Area of
Round Duct
Opening and
In. (mm) Dia Duct
Sq. In (Sq. mm)
6 (152) 20 (13043)
7 (178) 27 (17391)
8 (203) 34 (21739)
EXAMPLES: Determining Free Area
TOTAL INPUT
= (100,000 divided by 3,000)
= (110,000 divided by 2,000)
= (130,000 divided by 4,000)
50 26
Space Volume Ft
1,750 1,400
910 (25.8)
(49.5) (39.6)
1092
2,100 1,680
(59.4) (47.5)
(30.9)
1365
2,625 2,100
(74.3) (59.4)
(38.7)
1820
3,500 2,800
(99.1) (79.2)
(51.5)
5,250 2730 4,200
(148.6) (118.9)
(77.3)
5460
10,500 8,400
(297.3) (237.8)
(154.6)
NP NP
Specifications subject to change without notice.
c. Other openings are caulked or sealed. These include joints
around window and door frames, between sole plates and
floors, between wall- -ceiling joints, between wall panels,
at penetrations for plumbing, electrical and gas lines, etc.
Combination of Indoor and Outdoor Air
1. Indoor openings shall comply with the Indoor Combus-
tion Air Method below and,
2. Outdoor openings shall be located as required in the Out-
door Combustion Air Method mentioned previously and,
3. Outdoor openings shall be sized as follows:
a. Calculate the Ratio of all Indoor Space volume divided by
required volume for Indoor Combustion Air Method be-
low.
b. Outdoor opening size reduction Factor is 1 minus the Ra-
tio in a. above.
c. Minimum size of Outdoor openings shall be the size re-
quired in Outdoor Combustion Air Method above multi-
plied by reduction Factor in b. above. The minimum di-
mension of air openings shall be not less than 3 in. (80 mm).
(1 SQ. IN./3,000 BTUH)
(734 SQ. MM/KW)
Round Duct
In. (mm) Dia
5 (127)
6 (152)
7 (178)
= 33.3 Sq. In. for each Single Duct or Opening
= 55.0 Sq. In. for each two Horizontal Ducts
= 32.5 Sq. In. for each two Vertical Ducts or Openings
FAN-ASSISTED TOTAL
(1,000'S BTUH GAS INPUT RATE)
40 60 80
3 3
(M )
1,500 2,000
(42.5) (56.6)
1,800 2,400
(51.0) (67.9)
2,250 3,000
(63.7) (84.9)
3,000 4,000
(84.9) (113.2)
4,500 6,000
(127.3) (169.8)
9,000 12,000
(254.6) (339.5)
NP NP NP
TWO OPENINGS OR
VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH)
(550 SQ. MM/KW)
Free Area of
Round Duct
Opening and
Duct In. (mm) Dia.
Sq. In (mm)
15 (9678) 5 (127)
20 (12904) 5 (127)
25 (16130) 6 (152)
100 120 140
2,500 3,000 3,500
(70.8) (84.9) (99.1)
3,000 3,600 4,200
(84.9) (101.9) (118.9)
3,750 4,500 5,250
(106.1) (127.3) (148.6)
5,000 6,000 7,000
(141.5) (169.8) (198.1)
7,500 9,000 10,500
(212.2) (254.6) (297.1)
15,000 18,000 21,000
(424.4) (509.2) (594.1)
NP NP NP
440 01 4601 01