A.O. Smith BTH 120 - 250 - Manual (Page 4)

4
Temperature Time to Produce 2nd & 3rd
Setting Degree Burns on Adult Skin
180°F Nearly instantaneous
170°F Nearly instantaneous
160°F About 1/2 second
150°F About 1-1/2 seconds
140°F Less than 5 seconds
130°F About 30 seconds
120°F 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.
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 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.
FEATURES
IMPORTANT
IT IS REQUIRED THAT A QUALIFIED SERVICE TECHNICIAN PERFORM THE
INITIAL FIRING OF THE HEATER. AT THIS TIME THE USER SHOULD NOT
HESITATE TO ASK THE TECHNICIAN ANY QUESTIONS WHICH HE MAY
HAVE IN REGARD TO THE OPERATION AND MAINTENANCE OF THE UNIT.
A CHECKLIST AND SERVICE INFORMATION section are included at the rear
of this manual. By using this checklist the user may be able to make minor
operational adjustments and save himself unnecessary service calls.
However, the user should not attempt repairs which are not listed in this
section.
WATER TEMPERATURE CONTROL
DANGER
THIS WATER HEATER IS EQUIPPED WITH AN ADJUSTABLE THERMOSTAT
TO CONTROL WATER TEMPERATURE. HOT WATER TEMPERATURES
REQUIRED FOR AUTOMATIC DISHWASHER AND LAUNDRY USE CAN
CAUSE SCALD BURNS RESULTING IN SERIOUS PERSONAL INJURY AND/
OR DEATH. THE TEMPERATURE AT WHICH INJURY OCCURS VARIES WITH
THE PERSON’S AGE AND TIME OF EXPOSURE. THE SLOWER RESPONSE
TIME OF DISABLED PERSONS INCREASES THE HAZARDS TO THEM. NEVER
ALLOW SMALL CHILDREN TO USE A HOT WATER TAP, OR TO 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.
The water temperature is controlled using the Temperature Control Button
on the Display at the front of the unit (See Figure 1). This control utilizes
two temperature probes to determine the tank temperature. The primary
temperature probe is located at the top of the tank and the other is near the
water inlet.
The temperature may be adjusted from 80° to 180°F. The thermostat was
adjusted to 120°F before the heater was shipped from the factory. 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 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 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. If you experience this type of use, you should consider using
lower temperature settings to reduce scald hazards.