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Locked Condition; Maintenance And Service; Annual Maintenance; Winterizing For Seasonal Use - Bosch C 950 Installation Manual

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▶ Press "Program" key.
LCD shows pre-memorized temperature, which is now the hot water
selected temperature.

Locked condition

This condition is only valid for appliances with one or more remote
controls installed.
Fig. 68 Locked condition
Whenever LCD shows
, the temperature setting cannot be
adjusted because the appliance is in use by a user which already
selected a different temperature. Appliance will be automatically unlock
5 minutes after closing hot water tap.

Maintenance and service

▶ Always shut off the electrical power supply, shut off
the manual gas valve and shut off the water valves
whenever servicing.
▶ Inspect and clean the complete water heating system
once a year.
▶ Carry out maintenance as required. Immediately
repair all faults to avoid damage to the system.
Annual maintenance table
Inspect venting system
Inspect combustion chamber
Inspect burner
Inspect pressure relief
Inspect water filter
Inspect Heat
Fin Coils
Inspect condensate trap
Table 47 Annual maintenance

Annual maintenance

(To remove front cover, see page 8.)
Venting System
• Venting system - inspect inside of flue pipe for any blockage or
restriction. Observe burner flames during heater operation. (front
cover must be removed). Burner flames should be steady and blue.
Yellow, inconsistent (bouncing) flames may be an indication of poor
ventilation or combustion air supply. Inspect the combustion air inlet
pipe for blockage or debris. Inspect combustion air and exhaust
terminations for blockage or debris.
Every year
Combustion Chamber
• Inspect burner observation window (Fig.80, #14) for cracks or
spillage of flue gases. Observe burner flames during heater
operation. Flames should be steady and blue with no signs of
yellowing. Yellow burner flames are an indication of improper
combustion. Refer to Section 4.4, page 26, chapter 4.3, page 11 of
this manual to verify exhaust system and combustion air supply
meets manufacturer's specifications.
Pressure Relief
• Manually open the pressure relief valve to ensure proper operation.
Inlet Water Filter
• Verify the inlet filter screen is clean and undamaged. The inlet water
filter is located on the bottom of the appliance, to the right of the cold
water inlet fitting. (See Fig.36, page 32). Close installer supplied
water shutoff and remove wireform spring clip from filter. Remove
filter, clean and or replace if damaged.
• In areas where the water supply has a high mineral content, the heat
exchanger should be flushed with a descaling solution. Scale build up
will shorten the life of the water heater and damage resulting from
scale is not covered under warranty. Refer to section7.3 for detailed
instructions on descaling the heat exchanger.
Fin Coils
• Inspect heat exchanger fin coils for soot build-up or blockage. To
access fincoil, consult service bulletin at If
there is evidence of soot build-up or blockage, the heat exchanger
should be removed by a professional and cleaned thoroughly. Soot is
in indication of incomplete combustion and a clear sign of a serious
problem. Venting, gas pressure and flue gases should be examined to
determine the cause of the problem. Damage to the water heater
caused by incorrect installation or adjustment are not covered by the
manufacturer's warranty.
Condensate trap
• Check water level in the condensate trap, see fig. 38.
• If appliance is out of service for more than 10 days, fill as described
on page 33.
• Check for debris and clean if needed.

Winterizing for seasonal use

The water heater must not be installed in a location where it may be
exposed to freezing temperatures. If the heater must be left in a 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 and voids the warranty, 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 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
5. 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 inlet water connection until there is no water present
coming through the outlet water connection of the heater.
7. Reconnect water fittings and return heater to service when danger of
freezing has passed.
Maintenance and service | 41
6 720 805 440 (2014/11)



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This manual is also suitable for:

1050 esC 950 esC 1050 es