A.O. Smith DSE-5 Instruction Manual page 31

3. Characteristics of water supply.
Regardless of water treatment, the elements should be
examined regularly.
Lime scale accumulations may cause noises to occur during
operation.
It is recommended that a heating element be removed periodically
for examination. If it is scaled, all of the elements should be removed
and cleaned. If the tank bottom has an accumulation of sediment it
should be cleaned.
Lime scale should be removed by dissolving the accumulation in
UN-LIME delimer. Do not use muriatic or hydrochloric acid base
®
deliming solutions to remove lime scale from the elements.
THE PROCESS FOR LIME SCALE REMOVAL IS AS FOLLOWS:
1. Turn off electrical disconnect switch.
2. Drain the heater following DRAINING instructions.
3. Open front panel.
4. Disconnect the element wiring. Try not to disturb the wiring
unnecessarily and reconnection will be easier.
5. Unscrew each element.
6. Remove the elements and gaskets from the openings.
• Use a twisting, pulling action to remove elements scaled
beyond the size of the tank openings.
• Brush loose scale from elements.
7. Lime scale removal:
• Place limed ends of heating elements into UN-LIME delimer
and allow scale to dissolve. Do not permit delimer or water
to contact heating element electrical terminals.
• Silicates, sulfates, and aluminates must be removed
by scraping or other mechanical means. Lime scale
dissolvents will not remove these types of scale which are
occasionally encountered.
Call the toll free phone number on the back cover of this Instruction
Manual to purchase UN-LIME and heating element gaskets.
OTHER SCALE REMOVAL:
1. Flush cleaned ends of elements with water when deliming or
cleaning is completed.
2. Remove sediment and scale from the tank bottom through
the access provided by the element openings or drain valve
opening.
• The cold water inlet valve and drain valve may be opened
to aid the cleanout process.
3. Clean remaining gasket material from tank and element flanges.
Don not reuse original element gaskets.
4. Put new gaskets on each element and install into tank openings.
• Uniformly tighten element bolts. Torque to approximately
32 ft/lbs.
5. Attach element wires to connection points from which they were
removed.
6. Follow FILLING instructions to restore hot water service.
• Check for water leaks around elements and proper
operation when heater is filled.
• Close the panel.
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