Temperature Limiting Control(S); Temperature Regulation - A.O. Smith DRE Installation And Operation Manual

The pressure setting of the relief valve should not exceed the
pressure capacity of any component in the system. The
temperature setting of the relief valve should not exceed 210°F.
An unplugged 3/4" relief valve opening is provided for installing
temperature and pressure relief valve.

TEMPERATURE LIMITING CONTROL(S)

Both the DVE and DRE model water heaters incorporate high
temperature cutoffs. In the event of high temperature cutoff
operation, the reason for the operation of the high temperature
cutoff operation must be determined and corrected.
situation has been corrected the high temperature cutoff(s) may
be reset in the following manner:
DVE Models
The DVE models have a single immersion-type high temperature
cutoff control in the control circuit, see DVE CONTROL CIRCUIT
DIAGRAMS. This high temperature cutoff is factory set to open at
190°F (88°C). To manually reset the control you must:
1. Disconnect the power to the heater.
2. Allow the tank to cool to approximately 120°F.
3. Remove the front control cover.
4. Press the manual reset button. The control will not
reset until it has cooled approximately 50°F (28°C).
DRE Models
The DRE models have multiple surface mounted combination high
temperature cutoff and thermostat controls. There is one of these
combination high temperature cutoff and thermostat controls for
each element in a DRE model, see DRE CIRCUIT DIAGRAMS.
Each of the high temperature controls is of the manual reset type.
To manually reset the controls:
1. Disconnect the power to the heater.
2. Allow the tank to cool approximately 160°F.
3. Remove the front control cover.
4. Press the manual reset button on each of the effected
controls. The control will not reset until it has cooled
approximately 30°F (17°C).
Once the control(s) has been reset the control cover should be
replaced prior to operating the heater.

TEMPERATURE REGULATION

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 PERSONS AGE AND TIME OF EXPOSURE. THE SLOWER
RESPONSE TIME OF CHILDREN, AGED, OR DISABLED
PERSONS INCREASES THE HAZARDS TO THEM. NEVER ALLOW
Once the
DANGER
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.
SETTING THE WATER HEATER TEMPERATURES AT 120°F
WILL REDUCE THE RISK OF SCALDS. Some states require
settings at specific lower temperatures.
The water temperature is controlled in the DVE models with a
single thermostat located on the right front of the heater, just inside
the control cabinet. This control is set at 140°F at the factory and
has a fixed 5°F differential. The DRE models have multiple
thermostats depending on the configuration purchased. These
thermostats are also set at 140°F and have a 5-15°F differential.
A.O. Smith recommends setting the dial at the lowest setting which
produces an acceptable hot water supply. This will always give
the most energy efficient operation.
Figure 1 shows the approximate time-to-burn relationship for
normal adult skin.
Valves for reducing point-of-use temperature by mixing cold and
hot water are available. Also available are inexpensive devices
that attach to faucets to limit hot water temperatures. Contact a
licensed plumber or the local plumbing authority.
DRE MODELS
Temperature
Setting
180°F
170°F
160°F
150°F
140°F
130°F
120°F
6
DVE MODELS
Time to produce 2nd & 3rd
Degree burns on adult skin
Nearly instantaneous
Nearly instantaneous
About 1/2 second
About 1-1/2 seconds
Less than 5 seconds
About 30 seconds
More than 5 minutes
FIGURE 1