Mixing Valves
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 6 shows the approximate
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 (see Figure 8) or at the 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 6
Water Temperature | Time to Produce 2nd & 3rd | |
Degree Burns on Adult Skin | ||
|
180°F (82°C) | Nearly instantaneous |
170°F (77°C) | Nearly instantaneous |
160°F (71°C) | About 1/2 second |
150°F (66°C) | About |
140°F (60°C) | Less than 5 seconds |
130°F (54°C) | About 30 seconds |
120°F (49°C) | More than 5 minutes |
Dishwashing Machines
All dishwashing 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 dishwashing machine and should be adjusted to deliver water pressure between these limits.
HOT WATER
OUTLET
12” TO 15”
TEMPERED WATER
OUTLET
COLD |
| CHECK |
WATER |
| VALVE |
INLET |
| MIXING |
| CHECK | |
| VALVE | |
| VALVE | |
|
| |
| TO TANK | |
| INLET | |
Figure 8
The National Sanitation Foundation also recommends circulation of 180°F (82°C) water. Where this is done, the circulation should be very gentle so that it does not cause any unnecessary turbulence inside the water heater. The circulation should be just enough to provide 180°F (82°C) water at the point of
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 Water Piping Diagrams beginning on page 67.
Note: To comply with NSF Standard 5 installation 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.
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 flow preventers. Devices such as these cause the water system to be a closed system.
Thermal Expansion
As water is heated, it expands (thermal expansion). In a closed system the volume of water will grow when it is heated. As the volume of water grows there will be a corresponding increase in water pressure due to thermal expansion. Thermal expansion can cause premature tank failure (leakage). This type of failure is not 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. The Temperature- Pressure Relief Valve is not intended for the constant relief of thermal expansion.
A properly sized 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 Water Line Connections on page 40 and the Water Piping Diagrams beginning on page 67.
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