9
TYPICAL INSTALLATION
MIXING VALVES
DANGER
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.
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.
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.
TABLE 1.
Water
Temperature °F
Time for 1st Degree
Burn
(Less Severe Burns
Time for Permanent Burns
2nd & 3rd Degree
(Most Severe Burns)
110
(normal shower temp.)
Nearly instantaneous
116
(pain threshold)
Nearly instantaneous
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 second
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15,1978)
HOT WATER
OUTLET
TO TANK
INLET
CHECK
VALVE
MIXING
VALVE
COLD
WATER
INLET
TEMPERED WATER
OUTLET
12” TO 15”
(30-38 cm)
CHECK
VALVE
FIGURE 3
FIGURE 2.
MIXING VALVE / THERMAL EXPANSION TANK USAGE AND SPACE HEATING
Summary of Contents for 110
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