Bosch GWH 2700 ES LP - Manual (Page 33)

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Maintenance and service
33
space which is likely to experience freezing
temperatures, all water must be drained from the heater.
If precautions are not taken, resulting damage will not
be covered under the warranty. NOTE: Use of agents
such as anti-freeze is not permitted as they may cause
damage to the water heater's internal components.
1. Press ON/OFF switch on the water heater to turn
OFF the heater and unplug power supply cord. The
display should be blank.
2. Shut off gas supply to heater.
3. Shut off the water supply to the water heater using
installer supplied shutoff valve.
4. Open hot water taps to drain the plumbing system. If
water continues to flow after 5 minutes, a plumbing
crossover is present and must be corrected before
proceeding.
5. Open service valves (if available) or disconnect 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 outlet water connection
until there is no water present coming through the
inlet water connection of the heater.
7. Reconnect water fittings and return heater to service
when danger of freezing has past.
6.3 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
A7 and E9 and boiling sounds (knocking and banging)
in the heat exchanger.
Descaling using a pump
1. Disconnect electrical supply from the water heater.
2. Shut off the water supply to the water heater using
(installer supplied) shutoff valve.
3. Open hot water taps to drain and relieve pressure
from the plumbing system.
4. Drain water from the unit's heat exchanger by
disconnecting inlet and outlet water connections
from the heater.
5. Connect a line (A) from the outlet of the circulating
pump (installer supplied) to the inlet water fitting on
the water heater (see Fig. 54).
6. Using another line (B), connect to the water outlet
fitting on the water heater. Route the other end of this
line into a descaling reservoir.
7. Using a 3rd line (C) from the descaling reservoir,
connect to the inlet side of circulating pump. Install a
filter on the end of this line in the descaling reservoir.
8. Make sure all connections are "water tight.".
9. Fill tank with descaling solution so both lines inside
are submersed. We recommend straight white
vinegar. If using a commercial descalant, refer to
manufacturer's instructions on dilution with water.
10.Operate the circulating pump.
11.Make sure there are no leaks and the solution is
flowing from the descaling reservoir through the
heater and returning to the reservoir.
12.Run 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).
13.Disconnect all lines and drain all solution from heat
exchanger. Properly discard of solution.
14.Position a container below the hot water outlet and
connect cold water supply. Open cold water supply
isolation valve and flush heat exchanger with clean
water.
15.Shut cold water shutoff valve and reconnect hot
water supply to the water heater.
16.Reconnect electrical supply to unit, open water
shutoff valves, and return the unit to service.
Fig. 54
6.4 Adjusting CO
2
(carbon dioxide)
The CO
2
can only be adjusted by a certified gas
technician with a calibrated CO
2
analyzer.
Caution: One factor that may affect
CO
2
levels is improper gas pressure.
Please see Chapter 3.12 for the
procedure to measure gas pressure
and record your findings below: