A.O. Smith BTH 300A, BTH 400A warranty Water Temperature Setpoint Adjustment Procedure

The temperature may be adjusted from 80°F/27°C to 180°F/82°C. The thermostat 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.

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 SETPOINT AT ANY TIME BY USING THE FOLLOWING PROCEDURE. IN ALL CASES, INPUT POWER MUST BE APPLIED TO THE CONTROLLER TO PERFORM ANY PROGRAMMING OPERATIONS.

To change or view the current programmed temperature setpoint value, utilize the pushbutton on the Display Board. Momentarily pressing the button will briefly illustrate the existing setpoint value. If the button is held down for more than one second, the programming mode is automatically entered and the setpoint value will begin incrementing or decrementing by one degree per second. The control will alternate between the incrementing or decrementing mode each time the button is pressed. When the desired setpoint value is reached, simply release the button and the controller will automatically retain this value in temporary memory. After one complete heat cycle, the new setpoint is transferred to permanent memory.

Note: If power is interrupted prior to completing one heat cycle, the new setpoint will not be transferred to permanent memory. Therefore, it is a good practice to recheck the setpoint value at the end of a heat cycle after a new value has been entered.

If the button is held down long enough, the setpoint will reach 70°F (the minimum value) and stop. At this point, if the desired setpoint has not been obtained, release the button and depress it again. The setpoint value will now restart at 70°F and once again increase in value for as long as the button is pressed.

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.

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.

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, it must be manually reset by depressing the Temperature Adjustment Button/Reset Button on the display board. The water temperature must drop below 160°F/71°C before the controller can be reset.

Continued manual resetting of high limit control, preceded by higher than usual water temperature is evidence of high limit switch operation. 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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