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6. Louvers and Grilles: In calculating free area,
consideration should be given to the blocking effect of
louvers, grilles or screens protecting openings. Screens
used should not be smaller than 1/4 in. (0.64cm) 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 specifi ed. 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 should be fi xed 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 these chemicals. If necessary,
uncontaminated air should be obtained from remote or
outside sources.
WATER PIPING
HOT WATER CAN SCALD:
Water heaters are intended to produce hot water. Water
heated to a temperature which will satisfy space heating,
clothes washing, dish washing, cleaning and other sanitizing
needs can scald and permanently injure you upon contact.
Some people are more likely to be permanently injured by
hot water than others. These include the elderly, children,
the physically or developmentally disabled. If anyone using
hot water fi ts into one of these groups or if there is a local
code or state law requiring a certain temperature water at
the hot water tap, then you must take special precautions.
In addition to using the lowest possible temperature setting
that satisfi es your hot water needs, a means such as a
*mixing valve, should be used at the hot water taps used
by these people or at the water heater (see Figure 3).
Valves for reducing point of use temperature by mixing
cold and hot water are also available:
Consult a Qualifi ed Installer or Service Agency. Follow
manufacturer's instructions for installation of the valves.
Before changing the factory setting on the thermostat, read
the "Temperature Regulation" section in this manual.
This water heater should not be connected to any heating
systems or component(s) used with a non-potable water
heating appliance.
All piping components connected to this unit should be
suitable for use with potable water.
Toxic chemicals, such as those used for boiler treatment
should not be introduced into this system.
When the system requires water for space heating at
temperatures higher than required for domestic water
purposes, a mixing valve must be installed. Please refer
to Figure 3 for suggested piping arrangement.
CLOSED WATER SYSTEMS
Water supply systems may, because of code requirements
or such conditions as high line pressure, among others,
have installed devices such as pressure reducing valves,
check valves, and back fl ow preventers. Devices such as
these cause the water system to be a closed system.
THERMAL EXPANSION
As water is heated, it expands (thermal expansion). In a
closed system, the volume of water will increase. As the
volume of water increases, there will be a corresponding
increase in water pressure due to thermal expansion.
Thermal expansion can cause premature tank failure
19
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