Mixing Valves; Dish-Washing Machines; Closed Water Systems; Thermal Expansion - State Water Heaters 301 Series Instruction Manual

MIXING VALVES

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).
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.
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.
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 the lowest possible temperature setting that
satisfies the demand of the application, a mixing valve should be
installed at the water heater or at the hot water taps to further
reduce system water temperature. See
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 6. BURN TIME AT VARIOUS TEMPERATURES
Water Temperature Time for 1st Degree Burn
°F (°C) (Less Severe Burns)
110 (43) (normal shower temp.)
116 (47) (pain threshold)
116 (47) 35 minutes
122 (50) 1 minute
131 (55) 5 seconds
140 (60) 2 seconds
149 (65) 1 second
154 (68) instantaneous
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)

DISH-WASHING MACHINES

All dish-washing machines meeting the National Sanitation
Foundation requirements are designed to operate with water flow
pressures between 15 and 25 pounds per square inch (103 kPa
and 173 kPa). Flow pressures above 25 pounds per square inch
(173 kPa), or below 15 pounds per square inch (103 kPa), will
result in improperly sanitized dishes. Where pressures are high,
a water pressure reducing or flow regulating control valve should
be used in the 180°F (82°C) line to the dish-washing machine and
should be adjusted to deliver water pressure between these limits.
The National Sanitation Foundation also recommends circulation
of 180°F (82°C) water. The circulation should be just enough to
shows the
Table 6
provide 180°F (82°C) water at the point of take-off to the dish-
washing machine.
Adjust flow by throttling a full port ball valve installed in the
circulating line on the outlet side of the pump. Never throttle flow
on the suction side of a pump. See the
(page 69).
Note: To comply with
(page 14).
Figure 7

CLOSED WATER SYSTEMS

Water supply systems may, because of code requirements or such
conditions as high line pressure, among others, have installed
devices such as pressure reducing valves, check valves, and back
Time for Permanent Burns
flow preventers. Devices such as these cause the water system
2nd & 3rd Degree
to be a closed system.
(Most Severe Burns)

THERMAL EXPANSION

45 minutes
As water is heated, it expands (thermal expansion). In a closed
5 minutes
system the volume of water will grow when it is heated. As the
25 seconds
volume of water grows there will be a corresponding increase in
5 seconds
water pressure due to thermal expansion. Thermal expansion can
2 seconds
cause premature tank failure (leakage). This type of failure is not
1 second
covered under the limited warranty. Thermal expansion can also
cause intermittent Temperature-Pressure Relief Valve operation:
water discharged from the valve due to excessive pressure build
up. This condition is not covered under the limited warranty. See
Commercial Water Heater Limited Warranty
The Temperature-Pressure Relief Valve is not intended for the
constant relief of thermal expansion.
A properly sized and pressurized thermal expansion tank must
be installed on all closed systems to control the harmful effects
of thermal expansion. Contact a local plumbing service agency
to have a thermal expansion tank installed.
See
Diagrams
14
HOT WATER
OUTLET
TEMPERED WATER
OUTLET
COLD
WATER
INLET
CHECK
VALVE
TO TANK
Figure 7. Mixing Valve
NSF Standard 5
requirements, the bottom of the water heater must
be sealed to the floor with a silicone based sealant or
elevated 6 inches above the floor.
(page 43) and the
Water Line Connections
(page 69).
12" TO 15"
(30-38 cm)
CHECK
VALVE
MIXING
VALVE
INLET
Water Piping Diagrams
installation
(page 76).
Water Piping