Condensing Water Heater Service Manual 19 100000354
An “LC” or “00” error code indicates the unit is beginning to lime up and must be flushed. Failure to flush the
appliance will cause damage to the heat exchanger. Damage caused by lime build-up is not covered by the unit’s
warranty. After flushing, reset the LC fault code by turning off the power to the unit and turning the power back
on.
Flushing the Heat Exchanger
Water Heater
Pressure Relief Valve
3/4" Ball Valve
3/4" Union
Check Valve
S
Pressure Regulator
Circulating Pump
Solenoid Valve
Boiler Drain Valve
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V1
V3
V2
V4
H1
H2
H3
Circulating Pump
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Rinnai
1. Disconnect electrical power to the water heater.
2. Close the shutoff valves on both the hot water and
cold water lines (V3 and V4).
3. Connect pump outlet hose (H1) to the cold water line
at service valve (V2).
4. Connect drain hose (H3) to service valve (V1).
5. Pour 4 gallons of undiluted virgin, food grade, white
vinegar into pail.
6. Place the drain hose (H3) and the hose (H2) to the
pump inlet into the cleaning solution.
7. Open both service valves (V1 and V2) on the hot
water and cold water lines.
8. Operate the pump and allow the cleaning solution to
circulate through the water heater for at least 1 hour
at a rate of 4 gallons per minute (15.1 liters per
minute).
9. Turn off the pump.
10. Rinse the cleaning solution from the water heater as
follows:
a. Remove the free end of the drain hose (H3) from
the pail. Place in sink or outside to drain.
b. Close service valve, (V2), and open shutoff valve,
(V4). Do not open shutoff valve, (V3).
c. Allow water to flow through the water heater for 5
minutes.
d. Close shutoff valve (V4). When unit has finished
draining remove the in-line filter at the cold water
inlet and clean out any residue. Place filter back
into unit and open valve (V4).
e. Close service valve, (V1), and open shutoff valve,
(V3).
11. Disconnect all hoses.
13. Restore electrical power to the water heater.
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