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Operation And Maintenance; Function; Water Temperature Control; Appliance Adjustments - Bosch W11P Installation And Operating Instructions Manual

Gas instantaneous water heater
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Operation and maintenance

Sealed parts must not be interfered with.
3. 1


This water heater is fitted with piezo ignition that provides
for easy commissioning.
In first place it must dislocate the output control of the off
position to the ignition position (see fig. 5).
Press in the slide control knob and subsequently press the
piezo button. Release the slide control after about 15
seconds, if the pilot flame does not stay alight, repeat the
Ignition may not be successful due to the presence of air
inside the gas supply pipe, especially if first connected or
after long inactive periods. In this case, keep the output
control knob fully depressed until the gas pipe has been
totally purged.
Slide the gas control slide fully to the right to obtain maximum
output. Sliding the gas control slide to the left reduces the
In order to optimise energy consumption, adjust the output
control to supply the minimum output required.
After following these procedures, ignition of the main burner
will automatically take place whenever you turn on a hot
water tap, since the pilot burner is permanently alight.
When you want to switch off the heater, move the slide
control to the far left. After a few seconds the pilot flame
will go out.
If there is a risk of freezing, switch off the appliance and
drain the appliance.
Danger: the area in front of the burner can reach very high
temperatures, and there is a risk of burning on contact.

Water temperature control

The water temperature control is used to adjust the water
flow rate, and thereby the water temperature, to the desired
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
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.

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 (2,8 kPa).
Natural gas appliances are set to a Wobbe Index of 15 kWh/
and a supply pressure of 2.0 kPa.
* Sealed components must not be tampered with.
The appliance should only be serviced by an approved
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
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.

Flue gas safety device

The recommition must be done from a qualified technician
The flue gas safety device must not under any circumstances
be switched off, simulated or replaced by any other
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.
If faults occur on the flue gas safety device, proceed as
- Undo flue gas safety device fixing screw.
- Undo magnetic unit connector
- Remove thermocouple.
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.

Converting to a different gas type

Use only the genuine Bosch conversion kit. Conversion
may only be carried out by an approved technician.
6 720 607 526



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