Mixing Valves - A.O. Smith 120 Series Instruction Manual

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 °F
110
116
116
122
131
140
149
154
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)
COLD
WATER
INLET
9
TABLE 1.
Time for Permanent Burns
Time for 1 Degree Burns
st
2nd & 3rd Degree
(Less Severe Burns)
(Most Severe Burns)
(normal shower temp.)
(pain threshold)
35 minutes
1 minute
5 seconds
2 seconds
1 second
instantaneous
HOT WATER
OUTLET
12" TO 15"
(30-38 cm)
TEMPERED WATER
OUTLET
CHECK
VALVE
MIXING
CHECK
VALVE
VALVE
TO TANK
INLET
FIGURE 3
.
45 minutes
5 minutes
25 seconds
5 seconds
2 seconds
1 seconds