John Wood Atmospheric Gas (ENERGY STAR) - NEW - Manuel (Page 11)

11
Confined Space
For the correct and proper operation of this water heater,
ample air must be supplied for the combustion, ventilation,
and dilution of flue gases.
The size of each opening (free area) is determined by the
total BTUH input of all gas utilization equipment (i.e., water
heaters, furnaces, clothes dryers, etc.) and the method by
which the air is provided. The BTUH input can be found
on the water heater rating plate. Additional air can be
provided by two methods:
1. All air from inside the building.
2. All air from outdoors.
All Air from Inside the Building
When additional air is to be provided to the confined area
from additional room(s) within the building, the total volume
of the room(s) must be of sufficient size to properly provide
the necessary amount of fresh air to the water heater
and other gas utilization equipment in the area. If you are
unsure that the structure meets this requirement, contact
your local gas utility company or other qualified agency for
a safety inspection.
When indoor air is used, small enclosures and confined
areas must have two permanent openings so that sufficient
fresh air can be drawn from outside of the enclosure. The
bottom opening must be no lower than 6 inches (150 mm)
and no more than 18 inches (450 mm) above floor level.
The top opening must have the same area as the bottom
opening and be located as close to the ceiling as possible.
However, it must never be lower than the relief opening of
the draft hood. See Figure 6.
AS CLOSE TO CEILING AS POSSIBLE AND
PERMANENT
OPENINGS TO
ADDITIONAL
ROOMS WITHIN
THE BUILDING
CLOSET
OR
OTHER
CONFINED
SPACE
NO LESS THAN 6 INCHES (150 mm) AND
NO MORE THAN 18 INCHES (450 mm)
ABOVE FLOOR LEVEL.
ABOVE DRAFT HOOD.
FIGURE 6.
Each of the two openings shall have a minimum free area
of 1 square inch per 1,000 BTU/HR (2225mm² per kW) of
the total input rating of all gas utilization equipment in the
confined area, but not less than 100 square inches (645.16
cm 2 ). See Figure 7.
CONFINED
SPACE
PERMANENT
OPENINGS
1 SQUARE
INCH/1000
BTUH
(MINIMUM
100 SQ. IN.)
See text for
metric values.
FIGURE 7.
All Air from Outdoors
Outdoor fresh air can be provided to a confined area either
directly or by the use of ducts. The fresh air can be taken
from the outdoors or from crawl or attic spaces that freely
communicate with the outdoors. Attic or crawl spaces
cannot be closed and must be properly ventilated to the
outside.
Ductwork must be of the same cross-sectional area as the
free area of the opening to which they connect. The minimum
dimension of rectangular air ducts cannot be less than three
inches (76.2 mm). In addition, the duct must terminate within
1 foot (304.8 mm) above, and within 2 feet (609.6 mm)
horizontally from, the burner level of the appliance having the
largest input. See Figure 8.
BASEMENT INSTALLATION, EQUIPMENT LOCATED
IN CONFINED SPACES; ALL AIR FROM OUTDOORS
CONFINED
SPACE
GRADE
COMBINATION
COMBUSTION/
VENTILATION
AIR DUCT
12 in.
(304.8 mm)
MINIMUM
ABOVE GRADE
& SNOW LEVELS
WITHIN 12 in. (304.8 mm)
ABOVE BURNER LEVEL WITHIN 24 in. (609.6 mm)
FIGURE 8.
An opening may be used in lieu of a duct to provide the
outside air supply. It, too, must be located within 1 foot
(304.8 mm) above, and within 2 feet (609.6 mm) horizontally
from, the burner level of the applicance having the largest
input. However, it must be located at least 12 inches (304.8
mm) above the outside grade level and be clear of snow
levels. In addition, it must be equipped with a means to
prevent the direct entry of rain and wind without reducing
the required free area of the opening.