American Water Heater 120 series, Instruction Manual, Page: 22 / 52

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Table 5. Time to Burn Relationship for Normal Adult Skin
Water
Temperature °F
Time for 1st Degree Burn
(Less Severe Burns)
Time for Permanent
Burns 2nd & 3rd Degree
(Most Severe Burns)
131 5 seconds 25 seconds
140 2 seconds 5 seconds
149 1 second 2 seconds
154 instantaneous 1 second
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)
THERMOSTAT SETTINGS - ELECTRONIC CONTROLS
These models are equipped with an electronic control system.
The control system senses temperature from a factory installed
Immersion Temperature Probe (see Figure 3 ). The “Operating
Set Point” is adjusted to control water temperature. 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 - see Figure 15 ) located on the
front panel of the water heater.
The Operating Set Point is adjustable from 90°F/42°C to
190°F/88°C. The factory setting is 120°F/49°C. See the Electronic
Control Models Operation section of this manual for instructions
on how to adjust the Operating Set Point and other user settings.
Figure 15. UIM (User Interface Module)
Set the Operating Set Point at the lowest setting which produces
an acceptable hot water supply. This will always give the most
energy efficient operation.
CONTROL SYSTEM FEATURES
Advanced Diagnostics: Plain English text and animated icons
display detailed operational and diagnostic information. LCD screen
on the front of the water heater displays the Sequence of Operation
in real time. Fault or Alert messages are displayed when operational
problems occur. Advanced Service menu displays a list of possible
causes for current Fault and Alert conditions to aid in servicing.
Economy Mode Operation: Control system automatically
lowers the Operating Set Point by a programmed value during
user defined time periods. Helps reduce operating costs during
unoccupied or peak demand periods.
Linear Sequencing: Banks of heating elements (3 elements per
bank) are energized according to adjustable (1 to 20°) differential
set points for each bank. First bank on is the last bank off. Helps
reduce operating costs during low/moderate loads.
CONTROL SYSTEM NAVIGATION
The UIM (User Interface Module) is located on the front cabinet
of the Electronic Control Model water heaters. All operational
information and user settings are displayed and accessed using
the UIM. The UIM includes five snap acting (momentary) user
input buttons; an Up, Down and 3 Operational Buttons.
Figure 16. UIM - USER INTERFACE MODULE
UP & DOWN BUTTONS
Used to navigate (up and down) and to select (highlight) menu
items. Also used to adjust or change (increase/decrease, on/off,
set time) various user settings.
OPERATIONAL BUTTONS
The 3 Operational Buttons are multifunctional. Their current
function is defined by the text that appears above each button
on the LCD screen. The function will change depending on what
menu is currently displayed or what menu item is selected. When
no text appears on the LCD screen above an Operational Button
there is no function assigned.
THE DESKTOP SCREEN
Figure 17 below shows the control system “Desktop Screen.”
This is the default screen. If there are no active Fault or Alert
conditions and no user input for approximately 10 minutes the
control system will return to this screen automatically.
Model Information: Model information and menu titles are shown
in the black bar at the top of the Desktop Screen.
Tank Temperature:
Current water temperature as sensed from
the immersion Temperature Probe.
Operating Set Point:
Temperature at which the control system
will maintain tank (water) temperature in the Normal Mode. This
line of text will read Economy Set Point whenever the control
system is operating in the Economy Mode.
Status: The Operating State of the control system is displayed
beneath the Operating Set Point.
ELECTRONIC CONTROL MODELS OPERATION