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Installation Instructions
Gas
Vent
Gable
Vent
Ventilated
Attic
Optional
Top Above
Inlet (a)
Insulation
Outlet
Soffit
Air (a)
Vent
Gas
Water
Heater
Ventilated
Crawl Space
Figure 32
Ambient Combustion Air
WARNING: CARBON MONOXIDE POISONING HAZARD
This type of installation requires that the supply air to the
f
appliance( s) be of a sufficient amount to support all of
the appliance(s) in the area. Operation of a mechanical
exhaust, such as an exhaust fan, kitchen ventilation
system, clothes dryer or fireplace may create conditions
requiring special attention to avoid unsatisfactory
operation of gas appliances. A venting problem or a lack of
supply air will result in a hazardous condition, which can
cause the appliance to soot and generate dangerous levels
of CARBON MINOXIDE, which can lead to serious injury,
property damage and/or death.
An unconfined space is not less than 50 cu.ft (1.42m3) per 1,000Btu/hr
(0.2928 kW) input rating for all of the appliances installed in that area. Rooms
communicating directly with the space containing the appliances through openings
not furnished with doors are considered a part of the unconfined space.
In unconfined spaces (see definition below) in buildings, infiltration may be
adequate to provide air for combustion ventilation and dilution of flue gases.
However, in buildings of tight construction (for example, weather stripping, heavily
insulated, caulked, vapor barrier, etc.), additional air may need to be provided
using the methods described in "A confined space" section.
A confined space is an area with less than 50 cu . ft (1.42m3) per 1,000 Btu/
hr (0.2928 kW) input rating for all of the appliances installed in that area. The
following must be considered to obtain proper air for combustion and ventilation in
confined spaces.
Equipment Located in Confined Spaces:
a) All air from inside the building:
The confined space shall be provided with two permanent openings
communicating directly with an additional room(s) of sufficient volume so that
the combined volume of all spaces meets the criteria. The total input of all gas
utilization equipment installed in the combined space shall be considered in
making this determination. Each opening shall have a minimum free area of 1
square inch per 1,000 BTU per hour of the total input rating of all gas utilization
equipment in the confined space. One opening shall be within 12 inches of the
top and one within 12 inches of the bottom of the enclosure (See Table 11).
3 2 |
Gas
Vent
Gable
Vent
Ventilated
Attic
Top Above
Insulation
Soffit
Vent
Gas
Water
Inlet
Heater
Air (b)
BTUH Input Rating
60,000
80,000
100,000
120,000
Table 11
b) All air from outdoors:
60,000
80,000
100,000
120,000 60 sq.in (193 sq.cm)， 30 sq.in (194 sq.cm)
Table 12
EXAMPLE: Determining Free Area.
Appliance 1 Appliance
100,000 + 30,000 = (130,000 ， ÷ ， 4,000) = 32.5 Sq. In. Vertical
Appliance 1 Appliance
100,000 + 30,000 = (130,000 ÷ ， 2,000) = 65 Sq. In. Horizontal
Bosch 96% AFUE Condensing Gas Furnace - BTC 770503101 J (06.2023)
Outlet
Air (b)
Inlet
Inlet
Air (b)
Air (a)
Minimum Area in Square Inches Required for Each Opening
Minimum Free Area Required for Each Opening
BTUH
Input
Horizontal Duct
Opening to Outside
Rating
(2,000 BTUH)
30 sq.in (193 sq.cm)， 15 sq.in (193 sq.cm)
40 sq.in (193 sq.cm)
20 sq.in (129 sq.cm)
50 sq.in (193 sq.cm)
25 sq.in (161 sq.cm)
Minimum Area in Square Inch Required for Each Opening
Gas
Vent
Outlet
Air (a)
Gas
Water
Heater
Inlet
Air (a)
Minimum Free Area in Square Inch
Required for Each Opening
60 sq.in (387 sq.cm)
80 sq.in (516 sq.cm)
100 sq.in (645 sq.cm)
120 sq.in (516 sq.cm)
Vertical Duct or
Round Duct
(4,000 BTUH)
(4,000 BTUH)
， 5" (13 cm)
， 5" (13 cm)
， 6" (15 cm)
， 7" (18 cm)
2 Total Input
2 Total Input
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