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5656
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The time between cleaning will vary from two to six months
depending upon water conditions and usage. A change of
approximately 5
0
F in the normal temperature rise through the boiler
is usually an indication that scale should be removed. For long
life, copper or brass is recommended for all valves, pipe and fittings
used between gate valves “A” and “B” and the boiler, see fig. 51.
Boiler failure due to excessive lime build-up voids the warranty.
FIGURE 50
DELIMING SOLVENTS
A. O. Smith recommends the use of generic commercially available
cleaning solutions to remove lime buildup from your system.
CAUTION
Read the instructions on the label of the deliming solvent container.
REMOVING LIGHT DEPOSITS OF SCALE
1. Shut off electric and gas supply to the unit.
2. Close gate valves “A” and “B”, see fig.51.
3. Open drain cock and drain unit.
4. Remove pressure relief valve from outlet header assembly
and install drain hose assembly, see fig. 51.
5. Install standpipe in tee of inlet line, see fig. 51.
6. Close drain cock.
7. Slowly pour required amount of deliming solvent shown below
into unit through standpipe. Direct solution into suitable
container with hose, see illustration.
8. Continue to fill until foaming action stops.
9. When foaming action has stopped completely, allow 10 to
15 minutes for the solvent to dissolve any remaining scale in
the unit.
10. Open the drain cock and drain all the solvent from unit.
11. Remove standpipe and drain hose assembly from tees. Install
fittings originally removed into openings. Open valve “A”
allowing fresh water to flow through unit and out drain cock for
three to five minutes.
12. Close drain cock and open valve “B”. Restore electric and
gas supply.
Check unit for proper operation.
DELIMING THE HWB/HW BOILER
FIGURE 51
MINIMUM AMOUNT OF CLEANING
SOLUTION REQUIRED
Model
Number Litres Gallons
HWB/HW-300 12 3
HWB/HW-399 19 5
HWB/HW-420 19 5
HWB/HW-520 26 7
HWB/HW-610/670 26 7
HEAVY LIME DEPOSITS
If the solvent does not readily pass through the clogged coils or
heat exchanger, it will be necessary to use an acid pump deliming
kit, or contact a service agency for proper cleaning.
A. O. Smith part no. 4930 motorized deliming pump kit, complete
with pump, hoses, fittings, container and instructions is available
from your dealer, distributor or the A. O. Smith Water Products
Company.
REMOVING SILICATE
Ammonium bifluoride flakes (NH
4
F HF) can be used in conjunction
with delimer to delime and remove siliceous materials from copper
coil water boilers.
Ammonium bifluoride flakes should be purchased locally from
chemical suppliers.