GMES8 GCES8 Service Manual

PRODUCT DESIGN
22
9.3.5 Engineered Installations. Engineered combustion air installations
shall provide an adequate supply of combustion, ventilation, and dilution
air and shall be approved by the authority having jurisdiction.
9.3.6 Mechanical Combustion Air Supply. Where all combustion air
is provided by a mechanical air supply system, the combustion air shall
be supplied form outdoors at the minimum rate of 0.35 ft
3
/min per 1000
Btu/hr (0.034 m
3
/min per kW) for all appliances located within the space.
9.3.6.1 Where exhaust fans are installed, additional air shall be provided
to replace the exhausted air.
9.3.6.2 Each of the appliances served shall be interlocked to the mechanical
air supply system to prevent main burner operation where the mechanical
air supply system is not in operation.
9.3.6.3 Where combustion air is provided by the building’s mechanical
ventilation system, the system shall provide the specied combustion air
rate in addition to the required ventilation air.
9.3.7 Louvers, Grilles, and Screens.
9.3.7.1 Louvers and Grilles. The required size of openings for combus-
tion, ventilation, and dilution air shall be based on the net free area of
each opening. Where the free area through a design of louver or grille or
screen is known, it shall be used in calculating the size opening required
to provide the free area specied. Where the louver and grille design and
free area are not known, it shall be assumed that wood louvers will have
25 percent free area, and metal louvers and grilles will have 75 percent free
area. Nonmotorized louvers and grilles shall be xed in the open position.
9.3.7.2 Minimum Scree Mesh Size. Screens shall not be smaller than
1/4 in. mesh.
9.3.7.3 Motorized Louvers. Motorized louvers shall be interlocked with
the appliance so they are proven in the full open position prior to main
burner ignition and during main burner operation. Means shall be provided
to prevent the main burner form igniting should the louver fail to open
during burner startup and to shut down the main burner if the louvers
close during burner operation.
9.3.8 Combustion Air Ducts. Combustion air ducts shall comply with
9.3.8.1 through 9.3.8.8.
9.3.8.1 Ducts shall be constructed of galvanized steel or a material having
equivalent corrosion resistance, strength, and rigidity.
Exception: Within dwellings units, unobstructed stud and joist spaces
shall not be prohibited from conveying combustion air, provided that not
more than one reblock is removed.
9.3.8.2 Ducts shall terminate in an unobstructed space, allowing free
movement of combustion air to the appliances.
9.3.8.3 Ducts shall serve a single space.
9.3.8.4 Ducts shall not serve both upper and lower combustion air open-
ings where both such openings are used. The separation between ducts
servicing upper and lower combustion air openings shall be maintained
to the source of combustion air.
9.3.8.5 Ducts shall not be screened where terminating in an attic space.
9.3.8.6 Horizontal upper combustion air ducts shall not slope downward
toward the source of combustion air.
9.3.8.7 The remaining space surrounding a chimney liner, gas vent, special
gas vent, or plastic piping installed within a masonry, metal, or factory
built chimney shall not be used to supply combustion air.
Exception: Direct vent appliances designed for installation in a solid fu-
el-burning replace where installed in accordance with the manufacture’s
installation instructions.
9.3.8.8 Combustion air intake openings located on the exterior of the
building shall have the lowest side of the combustion air intake openings
located at least 12 in. (300 mm) vertically from the adjoining grade level.
Category I Venting (Vertical Venting)
(80% Furnaces Only)
WARNING
T
O PREVENT POSSIBLE PERSONAL INJURY OR DEATH DUE TO
ASPHYXIATION, NON-CONDENSING GAS FIRED WARM AIR FURNACES MUST
BE
CATEGORY I VENTED. DO NOT VENT ANY OF THESE FURNACES USING
C
ATEGORY
III
VENTING.
Category I Venting is venting at a non-positive pressure. A
furnace vented as Category I is considered a fan-assist-
ed appliance and does not have to be "gas tight." NOTE:
Single-Stage and Two-Stage gas furnaces with induced
draft blowers draw products of combustion through a heat
exchanger allowing in some instances common venting with
natural draft appliances (i.e. water heaters).
All installations must be vented in accordance with National
Fuel Gas Code NFPA 54/ANSI Z223.1 - latest edition. In
Canada, the furnaces must be vented in accordance with the
National Standard of Canada, CAN/CGA B149.1 and CAN/
CGA B149.2 - latest editions and amendments.
NOTE: The vertical height of the Category I venting system
must be at least as great as the horizontal length of the
venting system.
WARNING
TO PREVENT POSSIBLE DEATH OR PERSONAL INJURY DUE TO
ASPHYXIATION, COMMON VENTING WITH OTHER MANUFACTURER'S
INDUCED DRAFT APPLIANCES IS NOT ALLOWED.
When an existing furnace is removed from a venting system
serving other appliances, the venting system may be too
large to properly vent the remaining attached appliances. For
complete details refer to Exisiting Furnace Removal section
of this manual.