Advertisement
5750151-UIM-G-0423
COMBUSTION AIR
Figure 38: Combustion airflow path through the furnace casing
WARNING
!
This type of installation requires that the supply air to the 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 gen-
erate dangerous levels of CARBON MONOXIDE, which can lead to
serious injury, property damage and / or death.
An unconfined space is not less than 50 ft
(0.2928 kW) input rating for all of the appliances installed in that area.
Rooms communicating directly with the space containing the appli-
ances are considered part of the unconfined space, if doors are fur-
nished with openings or louvers.
A confined space is an area with less than 50 ft
Btu/h (0.2928 kW) input rating for all of the appliances installed in that
area. The following must be considered to obtain proper air for combus-
tion and ventilation in confined spaces.
Dampers, louvers and grilles
The blocking effects of louvers, grilles and screens must be given con-
sideration in calculating free area. If the free area of a specific louver or
grille is not known, see Table 10 to estimate free area.
Table 10: Estimated free area
Wood or Metal
Louvers or Grilles
Screens+
1/4 in. (6.4 mm) mesh or larger 100%
* Do not use less than 1/4 in. (6.4 mm) mesh.
+ Free area of louvers and grille varies widely; the installer should follow
louver or grille manufacturer's instructions.
Gable
Vent
Ventilated
Attic
Optional
Top Above
Inlet (a)
Insulation
Outlet
Soffit
Air (a)
Vent
Gas
Water
Heater
Ventilated
Crawl Space
Figure 39: Ambient combustion air
28
Vent pipe clamps
into outlet of
drain coupling
3
3
(1.42 m
) per 1,000 Btu/hr
3
3
(1.42 m
) per 1,000
Wood 20-25%*
Metal 60-70% *
Gas
Vent
Gable
Vent
Soffit
Vent
Inlet
Air (b)
1. The free area of a supply air opening shall be calculated by sub-
tracting the blockage area of all fixed louvers grilles or screens from
the gross area of the opening.
2. Apertures in a fixed louver, a grille, or screen shall have no dimen-
sion smaller than 1/4 in. (6.4 mm).
3. A manually operated damper or manually adjustable louvers are
not permitted for use.
4. A automatically operated damper or automatically adjustable lou-
vers shall be interlocked so that the main burner cannot operate
unless either the damper or the louver is in the fully open position.
When a Category I furnace is removed or replaced, the original vent-
ing system may no longer be correctly sized to properly vent the
attached appliances.
An improperly sized vent system can cause CARBON MONOXIDE to
spill into the living space causing personal injury, and or death.
Table 11: Unconfined space minimum area
Btu/h Input Rating
60,000
80,000
100,000
120,000
Table 12: Free area
Btu/h Input
Horizontal Duct
Rating
(2,000 Btu/h)
60,000
30 in
80,000
40 in
100,000
50 in
120,000
60 in
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
Gas
Vent
Ventilated
Attic
Top Above
Insulation
Gas
Water
Heater
Inlet
Air (a)
WARNING
!
Minimum Free Area
Required for Each Opening
2
60 in
(387 cm
2
80 in
(516 cm
2
100 in
(645 cm
2
120 in
(742 cm
Minimum free area required for each opening
Vertical Duct or
Opening to Outside
(4,000 Btu/h)
2
2
2
(193 cm
)
15 in
(97 cm
2
2
2
(258 cm
)
20 in
(129 cm
2
2
2
(322 cm
)
25 in
(161 cm
2
2
2
(387 cm
)
30 in
(193 cm
2 Total Input
2 Total Input
Outlet
Air (b)
Gas
Water
Inlet
Heater
Air (b)
Johnson Controls Ducted Systems
2
)
2
)
2
)
2
)
Round Duct
(4,000 Btu/h)
2
5 in. (13 cm)
)
2
5 in. (13 cm)
)
2
6 in. (15 cm)
)
2
7 in. (18 cm)
)
Gas
Vent
Outlet
Air (a)
Inlet
Air (a)
Advertisement
Need help?
Do you have a question about the YP9C Series and is the answer not in the manual?