A.O. Smith CAHP-120C Series, User Manual

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3. Complete the cleaning. Close the drain valve and remove the soft tube. Connect the water
heater to the power supply.
6.3 Cleaning the Precipitation
The sandy particles which are included in the impurities of water will deposit on the
bottom of the tank and produce precipitation. If the precipitation is not cleaned up in time, it
will get to the heating elements and cause a fault.
For convenience the cleaning of precipitation on the bottom of the tank and lime scale on
the surface of the heating elements should be performed simultaneously as the following
instruction.
6.4 Cleaning the Lime Scale (Perform once at least half a year)
It is a normal phenomenon that lime scale occurs on the surface of the heating elements
and it is normal to all immersion heating elements. The factors which affect the amount of
lime scale include:
1. The amount of hot water heated. More lime scale will occur along with the amount increase
of hot water.
2. Water temperature. More lime scale will form on the surface of the heating elements along
with the rising of the water temperature.
3. Water quality. No matter whether the water has been treated, the heating elements should
be checked regularly.
There may be noise during the operation after the lime scale is cleaned.
The damage of this water heater caused by too much scale accumulation will make the
quality guarantee become invalid.
It is recommended that the heating elements be removed to inspect regularly. If there is
scale, remove all the heating elements for cleaning. If there is precipitation on the bottom of
the tank, clean it.
The method of cleaning the lime scale is immersing the heating elements in UN.LIME
cleaning media or other cleaning media permitted by A.O.SMITH to dissolve the lime scale.
UN.LIME cleaning media is a non-chlorine cleaning media and can be bought from the
engineering service department. Whether it is under guarantee, the user should pay the cost
of material, labor and other relevant for cleaning the lime scale.
Performing Process
1. Disconnect the power supply to the water heater.
2. Drain the water in the tank completely according to the “Water Drainage” instruction.
3. Open the top and bottom service panels.
4. Remove the cover of the heating elements and disconnect the wire of the heating elements.
Do not mess the wires and it will be easy for connecting the wires again.
5. Screw out heating elements.
6. Remove heating elements from the openings. If the diameter of the heating element with
scale is more than that of the hole, screw the heating element and pull it out. Clean the scale
on the surface of the heating elements with a brush.
7. If cleaning the lime scale, immerse the section with scale of the heating element in
UN.LIME cleaning media to dissolve the lime scale. Do not let the electrical terminal of the
heating element contact with the cleaning media or water. If cleaning other scales, silicate,
sulfate and alumina should be cleaned by shaving or other mechanical means. These scales
may occur sometimes and cannot be cleaned by cleaning media of lime scale.