Mineral Scale Build-Up - Bosch Greentherm T9800 SEC 199 Installation And Operating Instructions Manual

left in a space which is likely to experience freezing
temperatures, all water must be drained from the heater.
NOTE: Use of agents such as anti-freeze is not permitted and
voids the warranty, as they may cause damage to the water
heater's internal components.
1. Hold ON/OFF switch on the water heater for 3 secs. to turn
OFF the heater and unplug the power supply cord. The
display should be blank.
2. Shut off the gas supply to the water heater.
3. Shut off the water supply to the water heater using installer
supplied shutoff valve.
4. Open hot water taps to drain and relieve pressure from the
plumbing system. If water continues to flow after 5
minutes, a crossover of the hot and cold water pipes is
present and must be corrected before proceeding.
5. Disconnect the inlet and outlet water pipes from the water
heater. Place a small bucket underneath the water heater
to catch residual water remaining inside the water heater.
6. Using an air compressor, blow short bursts of air (100psi
max) through the inlet water connection or inlet water filter
until there is no water present coming through the outlet
water connection of the heater.
7. Empty condensate trap.
8. Reconnect the water fittings and return the heater to
service when danger of freezing has passed.
7.3

Mineral scale build-up

Periodic descaling may be necessary in areas with high mineral
content in the water. Scale buildup in the heat exchanger may
result in lower flow rates, error codes of AA, E3,E5 and boiling
sounds in the heat exchanger.
A water softener is required if the water hardness exceeds 14
grains/gal (200 mg/l) calcium carbonate. Damage to the water
heater resulting from hard water/scale deposits will not be
covered under warranty.
Descaling using a pump
▶ Disconnect the electrical supply from the water heater.
▶ Shut off the water supply to the water heater.
▶ Open hot water taps to drain and relieve pressure from the
plumbing system.
▶ Shut off hot water valve to the water heater.
▶ Connect a line (A) from the outlet of the circulating pump
(installer supplied) to the inlet drain connection on the
water heater (see fig. 50.)
▶ Using another line (B), connect the outlet drain connection
on the water heater. Route the other end of this line into a
descaling reservoir.
▶ Using a 3rd line (C) from the descaling reservoir, connect
to the inlet side of circulating pump. Install a filter on the
end of the line in the descaling reservoir.
Greentherm T9800 SE 160/199 | SEC 199
▶ Make sure all connections are water tight.
▶ Fill the descaling reservoir with descaling solution so both
lines inside are submersed. We recommend a straight
white vinegar solution. If using a commercial descalant,
refer to manufacturer's instructions for proper dilution
ratio.
▶ Ensure both drain connections are open.
▶ Operate the circulating pump.
▶ Make sure there are no leaks and the solution is flowing
from the descaling reservoir through the heater and
returning to the reservoir.
▶ Run the solution through the heater until the solution
returning to the descaling reservoir comes out clear.
(Changing to a fresh solution may be necessary during this
process).
▶ Disconnect all lines and drain all solution from heat
exchanger. Properly discard the solution.
▶ Close the inlet drain connection.
▶ Position a container below the outlet drain connection and
connect the cold water supply. Open the cold water supply
shutoff valve and flush the heat exchanger with clean
water.
▶ Close the cold water shutoff valve and reconnect hot water
supply to the water heater.
▶ Close the outlet drain connection.
▶ Reconnect the electrical supply to the unit, open the water
shutoff valves, and return the unit to service.
Fig. 50
[1] Pump
[2] Water filter
Maintenance and service | 51
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