The temperature may be adjusted from 80°F/27°C to 180°F/82°C. The temperature was adjusted to 120°F/49°C before the heater was shipped from the factory. It is recommended that lower water temperatures be used to avoid the risk of scalding. It is further recommended, in all cases, that the water temperature be set for the lowest temperature which satisfies your hot water needs. This will also provide the most energy efficient operation of the water heater and minimize scale formation.

Valves for reducing point-of-use temperature by mixing cold and hot water are available (see Figure 2). Also available are inexpensive devices that attach to faucets to limit hot water temperatures. Contact a licensed plumber or the local plumbing authority.

WATER TEMPERATURE SETPOINT ADJUSTMENT

PROCEDURE

CAUTION

THE TEMPERATURE OF THE WATER AT THE TANK OUTLET MAY NOT CORRESPOND TO THE TEMPERATURE SETPOINT PROGRAMMED IN THE CONTROLLER. THE USER CAN EASILY CHANGE THE TEMPERATURE SETPOINTATANY TIME BY USING THE FOLLOWING PROCEDURE. IN ALL CASES, INPUT POWER MUST BE APPLIED TO THE CONTROLLER TO PERFORM ANY PROGRAMMING OPERATIONS.

The Operating Set Point of this water heater determines the regulated temperature for the water in the tank. This parameter is adjusted in the Temperature menu. Items in this menu allow you to monitor different temperature readings in the tank along with adjusting the Operating Set Point and Differential. To change the current programmed temperature setpoint value, see OPERATION section for details.

Figure 1 shows the approximate time-to-burn relationship for normal adult skin. Short repeated heating cycles caused by small hot water uses can cause temperatures at the point of use to exceed the thermostat setting by up to 20°F (11C°). If you experience this type of use, you should consider using lower temperature settings to reduce scald hazards.

Temperature

Time to Produce 2nd & 3rd

Setting

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 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

 

FIGURE 1.

FIGURE 2.

HIGH LIMIT SWITCH (E.C.O.)

The top immersion well of the dual bulb controller also contains the high limit (energy cutoff) sensor. The high limit switch interrupts the main burner gas flow should the water temperature reach approximately 202°F/94°C. Should the high limit switch activate, the water temperature must drop below 140°F/60°C before the controller can be reset. The following is a possible reason for high limit switch operation.

A malfunction in the thermostatic controls would allow the gas valve to remain open causing water temperature to exceed the thermostat setting. The water temperature would continue to rise until high limit switch operation.

Contact your dealer or servicer if continued high limit switch operation occurs.

DISHWASHING MACHINE REQUIREMENT

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 between these limits.

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 take-off to the dishwashing machine. Adjust flow by means of the plug cock in the circulating line. (See installation diagrams.)

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A.O. Smith 300A Water Temperature Setpoint Adjustment Procedure, High Limit Switch E.C.O, Dishwashing Machine Requirement