6
A) When communicating directly with the outdoors,
each opening shall have a minimum free area of one
(1) square inch per 4,000 BTUH (5.5 cm
2
/kW) of the
total input rating of all gas appliances in the enclo-
sure (see Figure 5).
B) When communicating with the outdoors through
vertical ducts, each opening shall have a minimum
free area of one (1) square inch per 4,000 BTUH (5.5
cm
2
/kW) of the total input rating of all gas appliances
in the enclosure (see Figure 6).
C) When communicating with the outdoors through
horizontal ducts, each opening shall have a mini-
mum free area of one (1) square inch per 2,000
BTUH (11.0 cm
2
/kW) of the total input rating of
all gas appliances in the enclosure (see Figure 7).
When ducts are used, they shall be of the same
cross-sectional area as the free area of the openings to
which they connect. The minimum short side dimension
of rectangular air ducts shall not be less than three (3)
inches (7.6 cm).
Louvers and Grilles
In calculating free area for ventilation and combustion
air supply openings, consideration must be given to the
blocking effect of louvers, grilles or screens protecting
the openings. Screens must not be smaller than
1
/4 inch
(6.4 mm) mesh. If the free area through a particular
design of louver or grille is known, it should be used in
calculating the size of opening required to provide the
free area specified. If the design and free area is not
known, it may be assumed that wood louvers and grilles
will allow 20-25% free area and metal louvers and grilles
will allow 60-75% free area. Louvers and grilles must
be installed in the open position or interconnect-
ed with the water heater so that they are opened
automatically during water heater operation.
Corrosive Atmospheres
If this water heater is to be installed in a beauty
shop, barber shop, photo processing lab, dry cleaning
establishment, a building with an indoor pool, or
near a chemical storage area, it is imperative that
the combustion and ventilation air be drawn from
outside these areas. These particular environments
contain products such as aerosol sprays, detergents,
bleaches, cleaning solvents, refrige rants, and other
volatile compounds that, in addition to being highly flam-
mable, become highly corrosive acid compounds when
burned. Exposure to such compounds can be hazardous
and lead to premature product failure.
Should the water heater fail, due to exposure to
such a corrosive atmosphere, the warranty is void.
INSTALLATION INSTRUCTIONS
Figure 7
Figure 6
Figure 5
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