Specifications
16
NFPA54 / ANSI Z223.1:
In this code the installation of a mechanical draft
system must meet the following requirements:
From this it is clear that any type of gas utilization
equipment, except for incinerators, can be vented
by means of a mechanical draft system. As the code
notes one exception only, this means that any type
replace, stove, gas heater, furnace etc. that is gas
red can be vented mechanically.
IFGC:
The International Fuel Gas Code is almost identical
to the National Fuel Gas Code, which is clear when
reviewing the following and comparing it to NFPA 54
Par. 10.3.4.:
12.4.3 Mechanical Draft Systems.
12.4.3.1 Mechanical draft systems shall be listed and
shall be installed in accordance with both the appliance
and the mechanical draft system manufacturer’s
installation instructions.
12.4.3.2 Appliances requiring venting shall be permitted
to be vented by means of mechanical draft systems of
either forced or induced draft design.
Exception: Incinerators.
12.4.3.3 Forced draft systems and all portions of induced
draft systems under positive pressure during operation
shall be designed and installed so as to prevent leakage
of ue or vent gases into a building.
12.4.3.4 Vent connectors serving appliances vented
by natural draft shall not be connected into any portion
of mechanical draft systems operating under positive
pressure.
12.4.3.5 Where a mechanical draft system is employed,
provision shall be made to prevent the ow of gas to the
main burners when the draft system is not performing so
as to satisfy the operating requirements of the appliance
for safe performance.
12.4.3.6 The exit terminals of mechanical draft systems
shall be not less than 7 ft (2.1 m) above grade where
located adjacent to public walkways and shall be located
as specied in 12.9.1 and 12.9.2.
(NFPA 54/ANSI Z223.1, 2009 Edition, pg. 84)
12.7.2 Gas Vent Termination. The termination of gas
vents shall comply with the following requirements:
(1) A gas vent shall terminate in accordance with
one of the following:
(a) Gas vents that are 12 in. (300 mm) or less
in size and located not less than 8 ft (2.4 m)
from a vertical wall or similar obstruction shall
terminate above the roof in accordance
with Figure 12.7.2 and Table 12.7.2.
(b) Gas vents that are over 12 in. (300 mm) in
size or are located less than 8 ft (2.4 m) from a
vertical wall or similar obstruction, shall
terminate not less than 2 ft (0.6 m) above
the highest point where they pass through the
roof and not less than 2 ft (0.6 m) above any
portion of a building within 10 ft (3.0 m)
horizontally.
(c) Industrial appliances as provided in 12.3.4.
(d) Direct-vent systems as provided in 12.3.5.
(e) Appliances with integral vents as provided in
12.3.6.
(f) Mechanical draft systems as provided in
12.4.3.
(f) Ventilating hoods and exhaust systems as
provided in 12.4.4.
(NFPA 54/ANSI Z223.1, 2009 Edition, pg. 54-87)
503.3.3 Mechanical Draft Systems. Mechanical draft
systems shall comply with the following:
1. Mechanical draft systems shall be listed and
shall be installed in accordance with the
manufacturer’s installation instructions for both
the appliance and the mechanical draft system.
2. Appliances, except incinerators, requiring
venting shall be permitted to be vented by
means of mechanical draft systems of either
forced or induced draft design.
3. Forced draft systems and all portions of induced
draft systems under positive pressure during
operation shall be designed and installed
so as to prevent leakage of ue or vent gases
into a building.
4. Vent connectors serving appliances vented by
natural draft shall not be connected into any
portion of mechanical draft systems operating
under positive pressure.
5. Where a mechanical draft system is employed,
provisions shall be made to prevent the ow
of gas to the main burners when the
draft system is not performing so as to satisfy
the operating requirements of the appliance for
safe performance.
6. The exit terminals of mechanical draft systems
shall be not less than 7 ft (2134 mm) above
grade where located adjacent to public
walkways and shall be located as specied
in Section 503.8, Items 1 and 2.
(IFGC, 2009 Edition, pg. 81)