Page 109 - 2018_IFGC

CHIMNEYS AND VENTS

503.12.6 Positioning. Draft hoods and draft regulators Category I appliances to maintain a nonpositive vent static
shall be installed in the position for which they were pressure when tested in accordance with nationally recog-
designed with reference to the horizontal and vertical nized standards.
planes and shall be located so that the relief opening is not FAN-ASSISTED COMBUSTION SYSTEM. An appliance
obstructed by any part of the appliance or adjacent con- equipped with an integral mechanical means to either draw or
struction. The appliance and its draft hood shall be located force products of combustion through the combustion cham-
so that the relief opening is accessible for checking vent ber or heat exchanger.
operation.
FAN Min. The minimum input rating of a Category I fan-
503.12.7 Clearance. A draft hood shall be located so its assisted appliance attached to a vent or connector.
relief opening is not less than 6 inches (152 mm) from any
surface except that of the appliance it serves and the vent- FAN Max. The maximum input rating of a Category I fan-
ing system to which the draft hood is connected. Where a assisted appliance attached to a vent or connector.
greater or lesser clearance is indicated on the appliance FAN + FAN. The maximum combined appliance input rat-
label, the clearance shall be not less than that specified on ing of two or more Category I fan-assisted appliances
the label. Such clearances shall not be reduced. attached to the common vent.
503.13 Manually operated dampers. A manually operated FAN + NAT. The maximum combined appliance input rat-
damper shall not be placed in the vent connector for any ing of one or more Category I fan-assisted appliances and one
appliance. Fixed baffles shall not be classified as manually or more Category I draft-hood-equipped appliances attached
operated dampers. to the common vent.
503.14 Automatically operated vent dampers. An automat- NA. Vent configuration is not allowed due to potential for
ically operated vent damper shall be of a listed type. condensate formation or pressurization of the venting system,
or not applicable due to physical or geometric restraints.
503.15 Obstructions. Devices that retard the flow of vent
gases shall not be installed in a vent connector, chimney or NAT Max. The maximum input rating of a Category I draft-
vent. The following shall not be considered as obstructions: hood-equipped appliance attached to a vent or connector.
1. Draft regulators and safety controls specifically listed NAT + NAT. The maximum combined appliance input rat-
for installation in venting systems and installed in ing of two or more Category I draft-hood-equipped appli-
accordance with the manufacturer’s instructions. ances attached to the common vent.
2. Approved draft regulators and safety controls that are 504.2 Application of single-appliance vent Tables 504.2(1)
designed and installed in accordance with approved through 504.2(6). The application of Tables 504.2(1)
engineering methods. through 504.2(6) shall be subject to the requirements of Sec-
tions 504.2.1 through 504.2.17.
3. Listed heat reclaimers and automatically operated vent
dampers installed in accordance with the manufac- 504.2.1 Vent obstructions. These venting tables shall not
turer’s instructions. be used where obstructions, as described in Section
503.15, are installed in the venting system. The installa-
4. Approved economizers, heat reclaimers and recupera-
tors installed in venting systems of appliances not tion of vents serving listed appliances with vent dampers
required to be equipped with draft hoods, provided that shall be in accordance with the appliance manufacturer’s
the appliance manufacturer’s instructions cover the instructions or in accordance with the following:
installation of such a device in the venting system and 1. The maximum capacity of the vent system shall be
performance in accordance with Sections 503.3 and determined using the “NAT Max” column.
503.3.1 is obtained. 2. The minimum capacity shall be determined as if the
5. Vent dampers serving listed appliances installed in appliance were a fan-assisted appliance, using the
accordance with Sections 504.2.1 and 504.3.1 or other “FAN Min” column to determine the minimum
approved engineering methods. capacity of the vent system. Where the correspond-
ing “FAN Min” is “NA,” the vent configuration
503.16 Outside wall penetrations. Where vents, including
those for direct-vent appliances, penetrate outside walls of shall not be permitted and an alternative venting
buildings, the annular spaces around such penetrations shall configuration shall be utilized.
be permanently sealed using approved materials to prevent 504.2.2 Minimum size. Where the vent size determined
entry of combustion products into the building. from the tables is smaller than the appliance draft hood
outlet or flue collar, the smaller size shall be permitted to
be used provided that all of the following requirements are
SECTION 504 (IFGS) met:
SIZING OF CATEGORY I 1. The total vent height (H) is not less than 10 feet
APPLIANCE VENTING SYSTEMS (3048 mm).
504.1 Definitions. The following definitions apply to the 2. Vents for appliance draft hood outlets or flue collars
tables in this section. 12 inches (305 mm) in diameter or smaller are not
APPLIANCE CATEGORIZED VENT DIAMETER/ reduced more than one table size.
AREA. The minimum vent area/diameter permissible for

96 2018 INTERNATIONAL FUEL GAS CODE ®
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