Temperature Regulation; High Temperature Limit Control (Eco); Thermostat Control - A.O. Smith BTH-120 Instruction Manual

high temperature limit control (eco)

This water heater is equipped with an ECO (energy cut out) 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 Upper Temperature Probe (two red
wires), see pages 8 and 9 for location. 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 Volt 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.

thermostat control

Water temperature over 125°F (52°C)
can cause severe burns instantly
resulting in severe injury or death.
Children, the elderly and the
physically or mentally disabled are at
highest risk for scald injury.
Feel water before bathing or
showering.
Temperature limiting devices such as
mixing valves must be installed
when required by codes and to
ensure safe temperatures at fixtures.
Hot water temperatures required for automatic dishwasher and
laundry use can cause scald burns resulting in serious personal
injury and/or death. Table 10 shows the approximate time-to-
burn relationship for normal adult skin.
The temperature at which injury occurs varies with the person's
age and duration of exposure. The slower response time of
children, the elderly or disabled persons increases the hazards
to them. If anyone using hot water provided by the water heater
being installed fits into one of these groups or if there is a local
code or state law requiring a certain water temperature at the
point of use, then special precautions must be taken.
In addition to using the lowest possible temperature setting that
satisfies the demand of the application a mixing valve can be
installed at the water heater (see Figure 8 on page 15) or at the hot
water taps to further reduce system water temperature.
Never allow small children to use a hot water tap or draw their own
bath water. Never leave a child or disabled person unattended in
a bathtub or shower.
The water heater should be located in an area where the general
public does not have access to set temperatures.

temperature regulation

Setting the Operating Set Point at 120°F (49°C) will reduce the
risk of scalds. Some States require settings at specific lower
temperatures.
taBle 10
Water Temperature Time for 1st Degree Burn
°F (°C) (Less Severe Burns)
110 (43) (normal shower temp.)
116 (47)
116 (47)
122 (50)
131 (55)
140 (60)
149 (65)
154 (68)
(U.S. Government memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)
The water heaters covered in this manual are equipped with
an electronic control system to regulate the water temperature
inside the storage tank. The control system senses temperature
from two factory installed temperature probes, one installed in
the top of the storage tank and one installed near the bottom,
See Top Views on page 8 and Figure 5 on page 10 for location.
The "Operating Set Point" is adjusted to regulate water
temperature inside the storage tank. This is an adjustable user
setting in the control system's "Temperatures menu." This and
all control system menus are accessed through the UIm (user
interface module) located on the front of the water heater, see
Figure 55.
The Operating Set Point is adjustable from 90°F (42°C) to 180°F
(82°C). The factory setting is 120°F (49°C). See Operating Set
Point And Differential Adjustment on page 47 for instructions on
how to adjust the Operating Set Point and other user settings.
Set the Operating Set Point at the lowest setting which produces
an acceptable hot water supply. This will always provide the most
energy efficient operation.
high temperature applications
Higher operating temperatures cause more wear on all water
heaters and will decrease the life span of the water heater.
Consider installing a small booster water heater for high
temperature applications, such as commercial dishwashers, to
raise the outlet temperature from the larger primary water heater
to the desired point of use temperature.
Contact your local distributor or call the technical support phone
number listed on the back cover of this manual for further
technical assistance.
MANUFACTURER / MODEL INFORMATION
Tank Temperature
Operating Set Point
Status: Heating
MENU
43
Time for Permanent Burns
2nd & 3rd Degree
(most Severe Burns)
(pain threshold)
35 minutes 45 minutes
1 minute 5 minutes
5 seconds 25 seconds
2 seconds 5 seconds
1 second 2 seconds
instantaneous 1 second
103°F
120°F
OFF
O
GAS
N
HELP
figure 55
UP
DN