A.O. Smith BTH 120-250(A) warranty Installation Instructions

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.

SETTING THE WATER HEATER TEMPERATURE AT 120°F/49°C WILL REDUCE THE RISK OF SCALDS. Some states require settings at specific lower temperatures.

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/11°C. 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 are possible reasons 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.)

CIRCULATING PUMP

A circulating pump is used when a system requires a circulating loop or there is a storage tank used in conjunction with the heater. Refer to the piping diagrams at rear of manual for electrical hookup information and install in accordance with the latest version of the National Electric Code NFPA 70 or Canadian Code CSAC22.1.

All bronze circulators are recommended for used with commercial water heaters.

Although circulators are oiled and operated by the manufacturer some circulators must be oiled again before operated. Please refer to manufacturer's instructions.

INSTALLATION INSTRUCTIONS

REQUIRED ABILITY

INSTALLATION OR SERVICE OF THIS WATER HEATER REQUIRESABILITY EQUIVALENT TO THAT OF A LICENSED TRADESMAN IN THE FIELD INVOLVED. PLUMBING, AIR SUPPLY, VENTING, GAS SUPPLY AND

ELECTRICAL WORK ARE REQUIRED.

INSULATION BLANKETS

Insulation blankets available to the general public for external use on gas water heaters are not approved for use on your A.O. Smith water heater. The purpose of an insulation blanket is to reduce the standby heat loss encountered with storage tank water heaters. Your A.O. Smith water heater meets or exceeds the ASHRAE/IES 90.1 1999 standards with respect to insulation and standby loss requirements, making an insulation

blanket unnecessary.

WARNING

Should you choose to apply an insulation blanket to this heater, you should follow these instructions. Failure to follow these instructions can result in fire, asphyxiation, serious personal injury or death.

•Do not apply insulation to the top, or the upper 15" (38 cm) of the water heater, as this will interfere with safe operation.

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