Figure 47
Circulating
Pump
H3
H2
H1
V1
V2
V3
V4
Hot water
line
Cold water
line
Gas supply line
56
Rinnai Tankless Water Heater Installation and Operation Manual
6.2 Flushing the Heat
Exchanger
This water heater includes a service indicated/
reminder (Service Soon,
SS
). When selected in
the parameter settings, an
SS
code will display on
the controller indicating that it is time to flush and
service the water heater. An LC diagnostic code
also 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 water heater’s warranty. Rinnai strongly
recommends installation of isolation valves to
allow for flushing of the heat exchanger.
1. Turn power on at the controller.
2. Disconnect electrical power from the source.
3. Close the shutoff valves on both the hot water
and cold water lines (V3 and V4).
4. Connect pump outlet hose (H1) to the cold
water line at isolation valve (V2).
5. Connect drain hose (H3) to the hot water line
at isolation valve (V1).
6. Pour four gallons of undiluted virgin, food
grade, white vinegar into pail.
7. Place the drain hose (H3) and the hose (H2)
to the pump inlet into the cleaning solution.
8. Open both isolation valves (V1 and V2) on the
hot water and cold water lines.
9. Restore power to the water heater for 20-30
sec. (this will open the water flow servo).
10. Disconnect electric power from the source.
11. Operate the pump and allow the vinegar to
circulate through the water heater for at least 1
hour at a rate of four gallons per minute (15.1
liters per minute).
12. Turn off the pump.
13. Rinse the vinegar 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 isolation valve (V2) and open shutoff
valve (V4). DO NOT open shutoff valve
(V3).
C. Allow water to flow through the water heat
-
er for five 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 isolation valve (V1) and open shutoff
valve (V3).
14. Disconnect all hoses.
15. Restore electrical power to the water heater.
Scale build-up will affect the performance of the
water heater. Water should be treated. Rinnai
offers water conditioning solutions that provide
superior lime scale prevention and corrosion
control by feeding a blend of scale control
compounds into the cold water supply. Refer to
section "3.5 Accessories" for more information.
NOTE
