Table of Contents
Advertisement
ii. Where communicating with the outdoors
through horizontal ducts, each opening shall
have a minimum free area of 1 in
Btu/hr (22 cm
input for all appliances in the space. See
Figure 1.6.
Figure 1.6:
Air Openings – All Air from Outdoors
through Horizontal Ducts
b. One Permanent Opening Method: Provide one
permanent opening beginning within 12 inches
(305 mm) of the top of the space. The opening
shall communicate directly with the outdoors,
communicate through a vertical or horizontal
duct, or communicate with a space that freely
communicates with the outdoors. The opening
shall have a minimum free area of 1 in
Btu/hr of total rated input for all appliances in
the space and not less than the sum of the cross-
sectional areas of all vent connectors in the space.
The gas-fired equipment shall have clearances of
at least 1 inch (25 mm) from the sides and back
and 6 inches (150 mm) from the front of the
appliance. See Figure 1.7 for this arrangement.
Figure 1.7:
Air Openings – All Air from Outdoors
through One Opening
2
per 2000
per 2000 W) of total rated
2
per 3000
2
6. Combination Indoor and Outdoor Combustion Air:
If the required volume of indoor air exceeds the
available indoor air volume, outdoor air openings or
ducts may be used to supplement the available indoor
air provided:
a. The size and location of the indoor openings
comply with Subsection 3.
b. The outdoor openings are to be located in
accordance with Subsection 4.
c. The size of the outdoor openings are to be sized
as follows:
( (
A
= A
x 1 –
req
full
where:
A
= minimum area of outdoor openings.
req
A
= full size of outdoor openings calculated
full
in accordance with Subsection 4.
V
= available indoor air volume
avail
V
= required indoor air volume
req
7. 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.
8. Mechanical Combustion Air Supply:
a. In installations where all combustion air is
provided by a mechanical air supply system,
the combustion air shall be supplied from the
outdoors at the minimum rate of 0.35 ft
1000 Btu/hr (0.034 m
total rated input of all appliances in the space.
b. In installations where exhaust fans are installed,
additional air shall be provided to replace the
exhaust air.
c. Each of the appliances served shall be interlocked
to the mechanical air supply to prevent main
burner operation when the mechanical air supply
system is not in operation.
d. In buildings where the combustion air is provided
by the mechanical ventilation system, the system
shall provide the specified combustion air rate in
addition to the required ventilation air.
9. Louvers & Grills:
a. The required size of openings for combustion,
ventilation, and dilution air shall be based on the
net free area of each opening.
i. Where the free area through a louver or grille
is known, it shall be used in calculating the
opening size required to provide the free area
specified.
ii. Where the free area through a louver or grille
is not known, it shall be assumed that wooden
louvers will have 25% free area and metal
louvers and grilles will have 75% free area.
iii. Non-motorized dampers shall be fixed in the
open position.
b. Motorized dampers shall be interlocked with the
equipment so that they are proven in the full open
position prior to ignition and during operation of
the main burner.
PREINSTALLATION
V
avail
V
req
/min per
3
3
/min per 1000 W) of the
5
Advertisement
Table of Contents
