A.O. Smith 317443-000, 100 Power Vent DV Series 120 Temperature regulation, HI Limit Switch ECO

temperature regulation

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 temperatures 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.

HOT WATER CAN SCALD: Water heaters are intended to produce hot water. Water heated to a temperature which will satisfy space heating, clothes washing, dish washing, and other sanitizing needs can scald and permanently injure you upon contact. Some people are more likely to be permanently injured by hot water than others. These include the elderly, children, the infirm, or physically/mentally handicapped. If anyone using hot water from this heater fits into one of these groups or if there is a local code or state law requiring a certain temperature water at the hot water tap, then you must take special precautions. In addition to using the lowest possible temperature setting that satisfies your hot water needs, a means such as a mixing valve, should be used at the hot water taps used by these people or at the water heater. Mixing valves are available at plumbing supply or hardware stores, see Figure 8. Follow manufacturer’s instructions for installation of the valves. Before changing the factory setting on the thermostat, read the “Temperature Regulation” section in this manual.

Never allow small children to use a hot water tap, or to draw their own bath water. Never leave a child or handicapped person unattended in a bathtub or shower.

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

The water temperature is controlled using the Temperature Control on the Display at the front of the unit (See Figure 1). This control utilizes a temperature probe to determine the tank temperature. The temperature probe is located behind the heater’s front display.

The temperature may be adjusted from 90°F/32°C to 160°F/71.1°C. The temperature was preset to 120°F/49°C before the heater was shipped from the factory. It is recommended that lower water temperature 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 the point-of-use temperature by mixing cold and hot water are available, see Figure 8. Also available are inexpensive devices that attach to faucets to limit hot water temperatures. Contact a licensed plumber or the local plumbing authority.

The table below 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.

	Time to Produce
Water Temperature	2nd & 3rd Degree
	Burns on Adult Skin
160° (71°C)	About 1/2 Second
150° (65°C)	About 1 1/2 Seconds
140° (60°C)	Less than 5 Seconds
130° (54°C)	More than 30 Seconds
120° (49°C)	More than 5 Minutes

HI LIMIT SWITCH (ECO)

This water heater is equipped with an ECO (energy cut off) non adjustable high temperature limit switch. The ECO is a normally closed switch that opens (activates) on a rise in temperature. The ECO is located inside the Temperature Probe (two red wires). The ECO switch contacts will open when the water temperature reaches approximately 202°F (94°C) and close at approximately 140°F (49°C).

If the ECO activates (contacts open) due to abnormally high water temperatures in the storage tank the control system will immediately de-energize the 24 VAC Gas Valve and end the current heating cycle. The control system will “lock out” disabling further heating operation. The control system will display the “Energy Cut Out (ECO)” Fault message on the LCD screen. It is important that a Qualified Service Agent be contacted to determine the reason for the ECO activation before resetting the ECO. Once the reason has been determined and corrected the ECO can be reset as follows:

Should the ECO activate, the water temperature must drop below 140°F (49°C) before the control system can be reset. Once the water temperature has cooled below this point the power supply to the water heater must be turned off and on again to reset the control system.

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

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