A.O. Smith DHE-10.000, Installation And Operaion Manual

Page: 15 / 20

15
instructions for installation of the valves. Before changing the factory
setting on the thermostat, read the entire “Temperature Regulation”
section in this manual.
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 thermostat be set for the lowest temperature
which satisfies your hot water needs. This will also minimize water
scale formations on the heating elements and provide the most
energy efficient operation of the water heater. Thermostat(s) are
factory set at 120°F (49°C) unless specified differently by state
requirements.
KEEPING THE THERMOSTAT SETTING AT 120°F WILL REDUCE
THE RISK OF SCALDS.
Figure 1 shows the approximate time-to-burn relationship for
normal adult skin.
teMperature adjustMent
Always close and lock the cabinet door after making a temperature
adjustment. Turn on electricity.
therMostat teMperature control
When the water heater cIrculatInG puMp (optional) is provided,
horizontal and vertical model heater thermostats may be set to 185°F
if dishwasher rinse water is supplied by the heater.
General
Water heater maintenance includes inspection and testing of the
Temperature Pressure Relief Valve, periodic tank flushing and
cleaning, and removal of lime scale from the heating elements.
Where used, water heating system circulating pumps should
be oiled.
Tank flushing and circulating pump lubrication should be
performed in accordance with the maintenance schedule, see
Table 6 on page 16. Tank sediment removal and element lime
scale removal must be performed when needed as determined
by periodic inspections.
anode InspectIon and replaceMent
This water heater is equipped with a sacrificial anode. Anodes
protect the glass-lined tank from corrosion by sacrificing
themselves through electrolysis. When the anode material is
consumed, there is no more protection and corrosion of the tank
accelerates.
Inspection of the anode every 6 to 12 months allows you to identify
a spent anode and replace it. Replace the anode when its diameter
is 3/8” (1 cm) of an inch, or annually which ever is first. Aggressive,
very hot and softened water causes rapid consumption of the
anode requiring frequent inspections. Anodes are available from
your distributor or A.O. Smith.
MaIntenance
wIthout the circulating pump, horizontal model heaters should be
set not higher than 165°F. Vertical models may be set as desired,
not to exceed 185°F.
Where MultIple therMostats are used on a vertical model
heater, they may all be set at the same temperature or 2° to 4°F apart
to achieve “step control”. The bottom thermostat is set the hottest
and the top thermostat the coolest.
Temperature Time to Produce 2nd & 3rd
Settings Degree Burns on Adult Skin
180°F (82°C) Nearly Instantaneous
160°F (71°C) About 1/2 second
150°F (66 °C) About 1-1/2 seconds
140°F (60°C) Less than 5 seconds
130°F (54°C) About 30 seconds
120°F (49°C) More than 5 minutes
80°F (27°C) - - - - - - - - - - - - - - - -
fIGure 1.
teMperature control (MechanIcal therMostat)
fIGure 2a.
solId state step control (wIth or wIthout ModulatIon)
Additional instructional literature is provided with the heater
sequencer control.
hIGh teMperature deVIces
A manual reset temperature high limit is in the control circuit
in addition to the automatic device previously described. The
contacts open at 210°F and must be manually reset after the
temperature hi-limit switch has been activated and the water
temperature is below 210°F.
The reset button is located on the temperature hi-limit in the
control cabinet of the heater. Disconnect the power before
opening the door to push the reset button.