23
The usage of water softening equipment greatly reduces the
hardness of the water. However, this equipment does not always
remove all of the hardness (lime). For this reason it is
recommended that a regular schedule for deliming be maintained.
The time between cleaning will vary from weeks to months
depending upon water conditions and usage. A change of
approximately 5
0
F in the normal temperature rise through the
heater 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 heater, see
fig. 18.
Heater failure due to excessive lime build-up voids the warranty
.
FIGURE 17
DELIMING SOLVENTS
A. O. Smith recommends the use of UN•LIME
®
for deliming.
UN•LIME is a patented food grade acid which is safe to handle
and does not create the harmful fumes which are associated with
other products.
UN•LIME may be obtained from your dealer, distributor or the
A. O. Smith Water Products Company. Order part no. 4763
(1 gal.), packed 4 gallons per case, or part no. 4813 (5 gal.
container).
CAUTION
Observe handling instructions on label of product being used.
REMOVING LIGHT DEPOSITS
1. Shut off electric and gas supply to the burner.
2. Close gate valves “A” and “B”.
3. Install drain hose assembly in upper deliming tee. Open drain
cock and drain heater. Install standpipe in lower deliming tee
or in tee from which pressure relief valve has been removed.
4. Close drain valve.
5. Slowly pour 3 gallons of UN•LIME into heater through
standpipe. Direct solution into suitable container with a hose,
see fig. 18.
DELIMING THE HW WATER HEATER
FIGURE 18
6. Continue to fill until foaming action stops.
7. When foaming action has stopped completely, allow 10 to 15
minutes for UN•LIME to dissolve any remaining scale in the
heater.
8. Open the drain valve and drain all UN•LIME from the heater.
9. Remove standpipe and drain hose assembly from tees. Install
fittings originally removed into openings. Open valve “A”,
allowing fresh water to flow through heater and out drain valve
for 3 to 5 minutes.
10.Close drain valve and open valve “B”. Heater is now ready for
operation.
HEAVY LIME DEPOSITS
If the solvent does not readily pass through the clogged coils or
heat exchanger, it will be necessary to use a deliming pump 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 A. O. Smith Water Products
Company.
A. O. Smith Form No. 4778, entitled “All About Deliming Coil Type
Water Heaters”, describes heater cleaning methods and
equipment required. UN•LIME and the booklet may be obtained
through your dealer, distributor or A. O. Smith Water Products
Company.
FIGURE 19
