Lennox COWB2

7
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You must provide enough fresh air to assure
proper combustion. The re in the boiler uses
oxygen. It must have a continuous supply. The
air in the house contains only enough oxygen
to supply the burner for a short time. Outside air
must enter the house to replace the air used by
the burner. Study the following examples 1 and 2
to determine your fresh air requirements.
EXAMPLE 1: Boiler Located in Unconned Space
If your boiler is in an open area (un-partitioned
basement) in a conventional house, the air that leaks
through the cracks around the doors and windows
will usually be adequate to provide air for combustion.
The doors should not t tightly. Do not caulk the cracks
around the windows.
An unconned space is dened as a space whose
volume is not less than 50 cubic feet per 1,000 Btu per
hour of the total input rating of all appliances installed
in that space.
WarNiNg
Be sure to provide enough fresh air for combustion.
Enough air ensures proper combustion and
assures that no hazard will develop due to the
lack of oxygen.
FresH air FOr COMBUsTiON
EXAMPLE 2: Boiler Located in Conned Space
A. All Air from Inside the Building: The conned
space shall be provided with two permanent
openings communicating directly with an additional
room(s) of sufcient volume so that the combined
volume of all spaces meets the criteria for an
unconned space. The total input of all combustion
equipment installed in the combined space shall
be considered in making this determination. Each
opening shall have a minimum free area of one
square inch per 1,000 Btu per hour of the total input
rating of all combustion equipment in the conned
space, but not less than 100 square inches. One
opening shall be within 12 inches of the top and one
within 12 inches of the bottom of the enclosure.
Example: Your boiler is rated at 100,000 Btu per
hour. The water heater is rated at 30,000 Btu per
hour. The total is 130,000 Btu per hour. You need
two grilles, each with 130 square inches of FREE
opening. Metal grilles have about 60% FREE
opening. To nd the louvered area needed, multiply
the free opening required by 1.7 (130 x 1.7 = 221.0
sq. in. louvered area). In this example, two grilles
each having an 8” x 30” (240 sq. in.) louvered area
would be used.
NOTE: If you use a replace or a kitchen or a bath-
room exhaust fan, you should install an outside air
intake. These devices will rob the boiler and water
heater of combustion air.
AIR OPENINGS FOR BOILER LOCATED IN
CONFINED SPACE
(Closet or Utility Room)