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6

6 720 607 527

3.

Operation and maintenance

Sealed parts must not be interfered with.

3.1

Function

This water heater is fitted with automatic electronic ignition
that provides for easy commissioning.
All that is required is to press the On/Off switch (Fig. 6).
The appliance will then ignite automatically as soon as a
hot water tap is turned on. The pilot flame ignites first and
then, about four seconds later, the main burner; the pilot
flame subsequently goes out after about 20 seconds.
Consequently, the appliance is substantially more
economical because the pilot flame only remains lit until
the main burner ignites, in contrast with conventional
appliances on which the pilot flame remains alight constantly.
After successful ignition, positioning it according to your
output requirement.

 

The further to the left you position the

output control the higher the output, and consequently the
higher the consumption of gas. Maximum output is obtained
when the slide control is to the far left.
In order to optimise energy consumption, adjust slide control
position to supply the minimum output required.
If there is air in the gas pipe when the appliance is
commissioned, this can cause ignition failure. In such cases,
the hot water tap should be turned off and then on again so
that the appliance repeats the ignition cycle. The procedure
should be repeated as necessary until the gas pipe is purged
of air.

Danger:

 the area in front of the burner can reach very high

temperatures, and there is a risk of burning on contact.

3.2

Water temperature control

The water temperature control is used to adjust the water
flow rate, and thereby the water temperature, to the desired
setting.
Turning the control clockwise reduces the water flow rate
and increases the temperature; turning the control anti-
clockwise increases the water flow rate and reduces the
temperature.
If the temperature is set only as high as required, energy
consumption is reduced and the likelihood of scale deposits
in the heat exchanger minimised.

3.3

Appliance adjustments

All instantaneous water heaters are factory-adjusted and
require no further adjustment.*
Water heaters that use LPG (liquefied petroleum gas, i.e.
butane/propane) are set to the operating pressure stated
on the identification plate (28 mbar).
Natural gas appliances are set to a Wobbe Index of 15 kWh/
m

3

 and a supply pressure of 20 mbar.

Sealed components must not be tampered with

.

3.4

Maintenance

The appliance should only be serviced by an approved
engineer.
A complete overhaul should be carried out after two years.
The overhaul should involve thoroughly cleaning the heat
exchanger, burner, pilot burner and automatic water valve
filter.
If necessary, the inside of the heat exchanger and the

connecting pipes should be descaled.
Check the gas and water valves for leaks and carry out a
complete function check.
If components need to be replaced, 

use only genuine Bosch

spare parts.

3.5

Flue gas safety device

The recommition must be done from a qualified technician
only.
The flue gas safety device must not under any circumstances
be switched off, simulated or replaced by any other
component.

Operation and safety precautions

The flue gas safety device checks the effectiveness of flue
gas extraction by the flue. If it is inadequate, the appliance
switches off automatically so that the combustion fumes do
not escape into the room in which the appliance has been
installed. The flue gas safety device resets after a cooling-
down period.
If the appliance shuts down while in operation, ventilate the
room. Wait about 10 minutes then restart the appliance. If
the problem recurs, call an engineer. The user must never
make any modifications to the appliance.

Maintenance*

If faults occur on the flue gas safety device, proceed as
follows:
- Undo flue gas safety device fixing screw.
- Unplug igniter unit connector
Replace damaged component with new one and refit using
the reverse of the procedure set out in the table above.

Function check

*

Flue gas safety device function check:
- Disconnect flue pipe
- Replace with pipe (about 50 cm long) with sealed end
- Fit pipe vertically
- Start up appliance at rated output and set temperature

control to maximum temperature.

Under those conditions, the appliance should shut down
after two minutes. Remove temporary pipe and reconnect
flue pipe.
* This work may only be carried out by an approved engineer.

3.6

Converting to a different gas type

Use only the 

genuine Bosch conversion kit

. Conversion

may only be carried out by an approved technician.

Summary of Contents for W11B

Page 1: ...d installer Do not use or store easily combustible materials in the vicinity of the appliance Gas Instantaneous Water Heater Installation and Operating Instructions Installation and servicing of the appliance may only be carried out by an approved technician The appliance should be regularly serviced in order to ensure that it remains in perfect and safe working order If there is a risk of freezin...

Page 2: ...es Semi permanent pilot flame functions only during the time between opening of the water valve and activation of the main burner Heat exchanger has no tin lead lining Automatic water valve made of glass fibre reinforced polyamide 100 recyclable Automatic control of water flow maintains constant flow rate even with fluctuating supply pressure Green LED indicates burner condition 1 2 Explanation of...

Page 3: ...arge level 24 Servo valve 25 Output control 26 Gas valve 27 Gas valve for pilot burner 28 Pilot burner injector 29 Igniter electrode 30 Pilot burner 31 Temperature limiter 32 Flue gas safety device 33 LED indicator for burner status 1 Outer case 2 Hole for fixing to wall 3 Observation window 4 Temperature control 5 LED indicator for battery charge level 6 On Off switch 7 Output control 8 Gas conne...

Page 4: ... 31420 40300 52082 Output modulation range Btu h 31420 65570 40300 80595 52082 104165 Rated max heat input Qn Btu h 74450 92210 117825 Rated min heat input Qmin Btu h 36200 46105 58912 Supply pressure Natural gas mbar kPa 20 2 0 20 2 0 20 2 0 LPG butane propane mbar kPa 28 2 8 28 2 8 28 2 8 Consumption Natural gas G20 m3 h 2 2 2 77 3 5 LPG butane propane G30 G31 kg h 1 75 2 2 2 79 Number of inject...

Page 5: ...ut control Remove the outer case by sliding it forwards and then lifting upwards Fix the appliance using the sleeves and hooks supplied so that it is vertical Never allow the appliance to rest against water or gas pipes 2 4 Water connection It is advisable to drain the appliance before installing it as any dirt or grit inside it could reduce the water flow rate and in extreme cases could completel...

Page 6: ...G liquefied petroleum gas i e butane propane are set to the operating pressure stated on the identification plate 28 mbar Natural gas appliances are set to a Wobbe Index of 15 kWh m3 and a supply pressure of 20 mbar Sealed components must not be tampered with 3 4 Maintenance The appliance should only be serviced by an approved engineer A complete overhaul should be carried out after two years The ...

Page 7: ...t water temperature Water not hot enough no flame Gas supply dynamic pressure too low Check gas cylinder governor and replace if incompatible or damaged Check whether gas cylinder butane is freezing when appliance is in operation and re site in warmer location if necessary Flame goes out while appliance is in operation Temperature limiter has tripped Wait 10 minutes then restart appliance If probl...

Page 8: ...ain burner on On I Off 0 Turning control anti clockwise increases water flow rate and reduces water temperature Turning control clockwise reduces water flow rate and increases water temperature Temperature adjustment Starting up Low water temperature Lower output High water temperature Higher output Safety precautions for use of batteries Do not dispose of batteries with normal household waste tak...

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