Descaling The Unit - A.O. Smith 110 Troubleshooting Manual

Hard water is a severe problem for the copper coils inside heat exchangers. Heat exchanger
failure due to scale buildup from hard water conditions is NOT covered by warranty. It is highly
suggested that a scale inhibitor be installed before the cold water inlet after this procedure is
done.
1) TOOLS ‐ Gather the following materials together:
Pump: The pump should provide a minimum of
a.
1GPM through the heater
Cleaning Solution: Food grade citric acid, food
b.
grade phosphorus acid.
Water hoses
c.
Bucket
d.
2) SETUP ‐ Disconnect power to the unit
3) WATERLINES – Assumes isolation valves with drain
ports are installed
Isolate the unit by closing the incoming/outgoing
a.
water isolation valves C and D.
Connect hoses/pump to the drain ports of the
b.
isolation valves: Outlet of the pump to valve B,
and another hose from Valve A to the bucket.
4) PUMP –
Fill the bucket with 5 gallons of diluted solution.
a.
Dilution ratio depends on the cleaning solution
used.
Place the pump into the bucket if it is submersible,
b.
or use an inlet hose into the bucket if it is not
submersible.
5) DESCALE
Open valves A and B.
a.
Circulate descaling solution through the unit for 45 minutes.
b.
6) CLEANSE THE SYSTEM – Flush the chemicals out of the heat exchanger with fresh water.
Close valve A and B.
a.
Open valve D and run fresh water through the PRV for 15 minutes.
b.
Clean the filter after flushing the unit with fresh water.
c.
Once the unit is flushed and cleansed, close A and B, open C and D, and reconnect power to the
d.
unit.
DESCALING THE UNIT
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Troubleshooting Guide
Figure 35
321923‐000