A.O. Smith 100 Power Vent DV Series 120, 317443-000 Mixing Valves, Dishwashing Machines

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 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 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 1
Water Temperature	Time to Produce 2nd & 3rd
	Degree Burns on Adult Skin
160°F (71°C)	About 1/2 second
150°F (66°C)	About 1-1/2 seconds
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 line to the dishwashing machine and should be adjusted to deliver water pressure between these limits.

		HOT WATER
		OUTLET
			12” TO 15”
TEMPERED WATER			(30-38 cm)
	OUTLET
COLD			CHECK
WATER			VALVE
INLET			MIXING
		CHECK
			VALVE
		VALVE
		TO TANK
		INLET

Figure 8.

Space heating and potable water system

Your water heater is equipped with inlet/outlet connections for use in space heating applications (see Figure 9). If this water heater is to be used to supply both space heating and potable (drinking) water, the instructions listed below must be followed:

•Be sure to follow the manual(s) shipped with the air handler or other type heating system.

•This water heater is not to be used as a replacement for an existing boiler installation.

•Do not use with piping that has been treated with chromates, boiler seal or other chemicals and do not add any chemicals to the water heater piping

•If the space heating system requires water temperatures in excess of 120°F, a tempering valve (provided) must be installed per the manufacturer’s instructions in the potable hot water supply to limit the risk of scald injury.

•Pumps, valves, piping and fi ttings must be compatible with potable water.

•A properly installed flow control valve is required to prevent thermosiphoning. Thermosiphoning is the result of a continuous flow of water through the air handler circuit during the off cycle. Weeping (blow off) of the temperature and pressure relief valve (T & P) or higher than normal water temperatures are the fi rst signs of thermosiphoning.

•The hot water line from the water heater should be vertical past any tempering valve or supply line to the heating system to remove air bubbles from the system.

•Do not connect the water heater to any system or components previously used with non-potable water heating appliances when used to supply potable water.

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