SERVICE PROCEDURES
SERVICE PROCEDURES
38 • On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models
Descaling the Unit
During operation, a tankless water
heater accumulates hard water
deposits on the interior surfaces of the
heat exchanger. These deposits make it
difficult to transfer heat into the water,
lowering the water heater’s efficiency
and causing excessive wear to the
components. Removing any deposits is
essential to the proper operation and
longevity of the water heater.
Tools and Materials:
Submersible transfer pump
3 gallons of 5% acidity white
vinegar (food grade), available
from most grocery stores
Washing machine hoses (2)
Five gallon bucket
Water heater isolation valve kits,
installed on both the cold water
inlet and hot water outlet of the
water heater (See Figure 27.)
1. Press the UP ARROW on the
temperature controller or remote
temperature controller to increase
the set temperature to 140°F.
To increase the temperature
above the 120- and 140-degree
safety stops, press and hold the
increase the temperature by
2.
2.1 Allow the water heater to
operate for 60 seconds.
2.2
Turn o power with the power
switch at the water heater’s
fuse box, by unplugging the
heater (indoor models), or
by turning o the associated
circuit breaker (outdoor
models).
3. Once power to the water heater
has been disconnected, close the
4.
5. Pour the white vinegar (3 gallons)
6. Connect one hose to the transfer
pump’s discharge outlet.
Connect its opposite end to the
7. Place the pump in the bucket of
vinegar.
8. Connect the second hose to the
outlet (A). Place its loose end into
the bucket with the vinegar.
Open the hot and cold service
10. Turn power to the pump on and
let it run.
11.
45 minutes.
12. Ensure that the bucket is placed
underneath the drain port. (See
Figure 17, page 32; see also
13. Remove the drain plug from the
drain port by turning it counter-
clockwise. See Figure 17, page
32.
NOTICE: Do not lose the O-ring.
14. Reinstall the drain port plug
drained out.
15.
and remove the hoses.
16.
D).
17.
nearest to the water heater
and let the water run for several
minutes to remove any remaining
vinegar from the water heater.
18. Close valve D.
Remove the drain port’s plug
again (Figure 17, p. 32), making
sure that the bucket is placed
underneath it.
20. Open valve D for about 10
through the drain port.
21. Close valve D.
22. Reinstall the drain port’s plug.
NOTICE: Be sure that the O-ring is still
attached at the end of the plug.
23. Open valve D again.
24. Turn power to the water heater
back on, then lower the set
temperature to where it was before
you began the descaling procedure.
25.
the water line, then close the open
Descaling the Water Heater
Figure 27.
On-Demand
Water
Heater
H C
A
B
C D
Pump
Outlet Hose
(Hot)
Inlet Hose
(Cold)
Descaling
Soluon
Gas Supply
Pressure Relief
Valve
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