PREINSTALLATION
5.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:
Areq = Afull | ⎛ | V | avail | ⎝ | |
⎜1 – | |||||
Vreq | ⎜ | ||||
| ⎝ | ⎛ | |||
where:
Areq = minimum area of outdoor openings. Afull = full size of outdoor openings calculated
in accordance with Subsection 4. Vavail=available indoor air volume Vreq = required indoor air volume
6.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.
7.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 ft3/min per 1000 Btu/hr (0.034 m3/min per 1000 W) of the 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.
8.Louvers & Grills:
iii.Nonmotorized 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.
i.The interlock shall prevent the main burner from igniting if the damper fails to open during burner startup.
ii.The interlock shall shut down the burner if the damper closes during burner operation.
9.Combustion Air Ducts
a.Ducts shall be constructed of galvanized steel or an equivalent corrosion- resistant material.
b.Ducts shall terminate in an unobstructed space, allowing free movement of combustion air to the appliances.
c.Ducts shall serve a single space.
d.Ducts shall not serve both upper and lower combustion air openings where both such openings are used. The separation between ducts serving upper and lower combustion air openings shall be maintained to the source of combustion air.
e.Ducts shall not be screened where terminating in an attic space.
f.Horizontal upper combustion air ducts shall not slope downward toward the source of the combustion air.
g.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.
h.Combustion air intake openings located on the exterior of buildings shall have the lowest side of the combustion air intake opening at least 12 inches (305 mm) above grade.
D.CHIMNEY OR VENT
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.
1.Inspect the existing chimney or vent system. Make sure it is in good condition. Inspect chimney liner and repair or replace if necessary.
2.The vent system and installation must be in accordance with the current edition of the National Fuel Gas Code, ANSI Z223.1/NFPA 54, under “Venting of Equipment”, or CAN/CGA B149, Installation codes, under “Venting Systems and Air Supply for Appliances”, or applicable provisions of the local building codes.
5
