100221773_2000189439_Rev. 01
www. lochinvar .com
19
3. When communicating with the outdoors through
horizontal ducts, each opening shall have a
minimum free area of 1 square inch per 2,000
Btu/hr of total input rating of all equipment in the
enclosure (see Figure 20).
Figure 19.
4. 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 3 in. (see Figure 20).
Figure 20.
5. Alternatively a single permanent opening may
be used when communicating directly with the
outdoors, or with spaces that freely communicate
with the outdoors. The opening shall have a
minimum free area of 1 square inch per 3,000 Btu/
hr of total input rating of all equipment in enclosure
(see Figure 21).
Figure 21.
6. Louvers and Grilles: In calculating free area,
consideration shall be given to the blocking effect
of louvers, grilles or screens protecting openings.
Screens used shall not be smaller than 1/4 in.
mesh. If the free area through a design of louver
or grille is known, it should be used in calculating
the size opening required to provide the free
area specified. If the design and free area is not
known, it may be assumed that wood louvers will
be 20-25 percent free area and metal louvers and
grilles will have 60-75 percent free area. Louvers
and grilles shall be fixed in the open position or
interlocked with the equipment so that they are
opened automatically during equipment operation.
7. Special Conditions Created by Mechanical
Exhausting or Fireplaces: operation of exhaust
fans, ventilation systems, clothes dryers or
fireplaces may create conditions requiring special
attention to avoid unsatisfactory operation of
installed gas utilization equipment.
CHEMICAL VAPOR CORROSION
CORROSION OF THE FLUEWAYS AND VENT SYSTEM
MAY OCCUR IF AIR FOR COMBUSTION CONTAINS
CERTAIN CHEMICAL VAPORS. SUCH CORROSION
MAY RESULT IN FAILURE AND RISK OF ASPHYXIATION.
Spray can propellants, cleaning solvents, refrigerator and
air conditioning refrigerants, swimming pool chemicals,
calcium and sodium chloride (water softener salt), waxes,
and process chemicals are typical compounds which
are potentially corrosive. Do not store products of this
sort near the heater. Also air which is brought in contact
with the heater should not contain any of the chemicals.
If necessary, uncontaminated air should be obtained
from remote or outside sources. The Limited Warranty is
voided when failure of water heater is due to a corrosive
atmosphere. See Limited Warranty for complete terms
and conditions.