A.O. Smith Vertex 100 Power Vent DV Series 120, Instruction Manual, Page: 36 / 60

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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.
Water Temperature
Time to Produce
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.
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
teMperature reGulatIon