A.O. Smith DIRECT VENTED GAS MODELS, Installation And Operating Manual

Page: 14 / 48

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WATER PIPING
Water Pressure
The water supply pressure should not exceed 80 psi. If this
occurs, a pressure reducing valve with a bypass should be
installed in the cold water inlet line. This should be placed
on the supply to the entire house in order to maintain equal
hot and cold water pressures. See also “Closed Water
Systems” and “Thermal Expansion” sections.
Mixing Valves
HOT WATER CAN SCALD:
Water heaters are intended to heat 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.
Short repeated heating cycles caused by small hot water
uses can cause a temperature increase of the hot water
by 20F° higher than the heater’s temperature settings.
MIXING VALVE
SHUT-OFF
VALVE
SUGGESTED PIPING
ARRANGEMENT FOR
TOP CONNECTIONS
COLD WATER
INLET
TEMPERED
POTABLE WATER
DISCHARGE
PIPE (DO NOT
CAP OR PLUG)
GAS
SUPPLY
TEMPERATURE-
PRESSURE
RELIEF VALVE
DRAIN
VALVE
METAL DRAIN
PAN
6 ” MAX.
AIR GAP*
CERTAIN
MODELS ARE
EQUIPPED WITH
SIDE PLUMBING
CONNECTIONS
FOR SPACE
HEATING. THE HOT
AND COLD FITTING
ASSEMBLIES
(PART #9001262)
CAN BE ORDERED
THROUGH THE
MANUFACTURER
MASSACHUSETTS: INSTALL A VACUUM RELIEF IN COLD-WATER LINE
PER SECTION 19 MGL 142.
Figure 8
Water temperature over
125°F can cause severe
burns instantly resulting in
severe injury or death.
Children, the elderly and the
disabled and are at highest
risk of scald injury.
Feel water before bathing or
showering.
Temperature limiting devices
such as mixing must be
installed when required by
codes and to ensure safe
temperatures at fixtures.
BURN
HOT
HOT
DANGER
Some people are more likely to be permanently injured
by hot water than others. These include the elderly,
children, the in
fi rm and the physically/mentally disabled.
Table 1 (published by U.S. Government Memorandum,
1978) shows the approximate time-to-burn relationship
for normal adult skin. If anyone using hot water provided
by the water heater being installed
fi ts into one of these
groups or if there is a local code or state law requiring a
certain water temperature at the point of use, then special
precautions must be taken (see Figure 8).
Water
Temperature
°F
Time for 1st
Degree Burns
(Less Severe Burns)
Time for Permanent
Burns 2nd & 3rd
Degree (Most
Severe Burns)
110 (normal shower temp.)
116 (pain threshold)
116 35 minutes 45 minutes
122 1 minute 5 minutes
131 5 seconds 25 seconds
140 2 seconds 5 seconds
149 1 second 2 seconds
154 instantaneous 1 seconds
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong,
Sept. 15,1978)
Table 1
In addition to using lowest possible temperature setting
that satis
fi es demand of application, a mixing valve should
be installed at the water heater (see Figure 8) or at hot
water taps to further reduce system water temperature.
Mixing valves are available at plumbing supply stores.
Consult a Quali
fi ed Installer or Service Agency. Follow
mixing valve manufacturer’s instructions for installation
of the valves. Before changing the factory setting on the
thermostat, read the “Operating The Temperature Control
System” section in this manual.