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12
FIGURE 13
• Whenductsareused,theyshould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 should not be less than 3 inches (76.2 mm), see
Figure 14.
FIGURE 14.
• 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 inch (6.4 mm) 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speci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
xedintheopenpositionorinterlockedwiththeequipment
so that they are opened automatically during equipment
operation.
• SpecialConditionsCreatedbyMechanicalExhaustingor
Fireplaces: operation of exhaust fans, ventilation systems,
clothesdryersorreplacesmaycreateconditionsrequiring
special attention to avoid unsatisfactory operation of
installed gas utilization equipment.
WaterPiping
HOTTER 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inrm,orphysically/mentallyhandicapped.Ifanyone
usinghotwaterinyourhome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satis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. Mixing valves are available at plumbing supply or
hardware stores, see Figure 15 below. Valves for reducing
point of use temperature by mixing cold and hot water
are also available.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.
FIGURE 15.