A.O. Smith BTX-80 SERIES 100 Instruction Manual page 9

MIXInG valve / therMal eXpansIon tanK usaGe and space heatInG
MIXInG valves
DANGER
Water heated to a temperature which will satisfy clothes washing, dish
washing, and other sanitizing needs can scald and cause permanent
injury upon contact. Short repeated heating cycles caused by small
hot water uses can cause temperatures at the point of use to exceed
the water heater's temperature setting by up to 20°F (11°C).
Some people are more likely to be permanently injured by hot water
than others. These include the elderly, children, the infirm and the
physically/mentally disabled. Table 1 shows the approximate time-
to-burn relationship for normal adult skin. If anyone using hot water
provided by the water heater being installed fits 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.
In addition to using lowest possible temperature setting that satisfies demand
of application a Mixing Valve should be installed at water heater (see Figure
3) or at hot water taps to further reduce system water temperature.
tYpIcal InstallatIon
Water temperature over 125°F (52°C)
can cause severe burns instantly
resulting in severe injury or death.
Children, the elderly and the physically
or mentally disabled are at highest risk
for scald injury.
Feel water before bathing or showering.
Temperature limiting devices such as
mixing valves must be installed when
required by codes and to ensure safe
temperatures at fixtures.
fIGure 2.
Mixing valves are available at plumbing supply stores. Consult a
Qualified Installer or Service Agency. Follow mixing valve manufacturer's
instructions for installation of the valves.
Water Temperature
180°F (82°C)
170°F (77°C)
160°F (71°C)
150°F (66°C)
140°F (60°C)
130°F (54°C)
120°F (49°C)
TEMPERED WATER
COLD
WATER
INLET
9
taBle 1.
Time to Produce 2nd & 3rd
Degree Burns on Adult Skin
Nearly instantaneous
Nearly instantaneous
About 1/2 second
About 1-1/2 seconds
Less than 5 seconds
About 30 seconds
More than 5 minutes
HOT WATER
OUTLET
12" TO 15"
(30-38 cm)
OUTLET
CHECK
VALVE
MIXING
CHECK
VALVE
VALVE
TO TANK
INLET
fIGure 3 .