Bosch Zwb283 Manual

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Fig. 2  
Page 29 contains a quick reference. You can fold this outward and 
keep these operating instructions in the control panel cover. 
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4.1 Overview of controls
Fig. 3  
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[1] Emission test button for contractors (see installation instructions)
[2] Service button for contractors (see installation instructions)
[3] Burner ON indicator lamp
[4] ON/OFF switch
[5] Key pad lock
[6] ECO button
[7] Reset button
[8] Display
[9] Boiler water pressure gauge
[10] DHW thermostat
[11] Safety relief valve discharge hose
[12] Condensate drain hose
[13] Heating return pipe
[14] Cold water pipe - combi boiler only
[15] Gas pipe
[16] DHW pipe - combi boiler only
[17] Supply pipe
[18] Boiler high limit dial
[19] Mounting socket for outdoor reset controls 
						

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4.2 Switching the appliance ON/OFF
Startup
▶ Switch the appliance ON using the ON/OFF switch.
The display shows the supply temperature.
Fig. 4  
Shutdown
▶ Switch the appliance OFF using the ON/OFF switch.
The diplay goes out.
▶ If the appliance is taken out of service for a longer period: Observe frost 
protection ( Section 4.8).
4.3 Turning the space heating ON
The maximum supply temperature can be set from 95 °F (35 °C) up to approx. 
194 °F (90 °C). The current supply temperature is shown on the display.
If the display shows   in alternation with the supply temperature, 
the appliance operates at its lowest output for 15 minutes per the 
initial startup sequence.
With radiant floor heating, limit the maximum permissible supply 
temperature.
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▶ Adjusting the supply temperature with the boiler high limit dial  :
– Radiant floor heating: e.g. setting 3 (approx. 122 °F (50 °C))
– Panel or cast iron radiator heating: setting 6 (approx. 167 °F (75 °C))
– Heating with supply temperatures up to 194 °F (90 °C): setting max 
Fig. 5  
The burner ON indicator lamp lights up if the burner is operating.
Boiler high limit 
dial Typical supply 
temperaturesSample application
1 approx. 95 °F (35 °C)Frost protection
2 approx. 109 °F (43 °C)
3 approx. 122 °F (50 °C)Radiant floor heating system
4 approx. 140 °F (60 °C)
5 approx. 153 °F (67 °C)
6 approx. 167 °F (75 °C)Radiator heating system
max approx. 194 °F (90 °C)Convector heating
Table 3   Typical supply temperatures
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4.4 Programming the heating control unit
Fig. 6  
4.5 ZBR..-3A appliances with DHW tank: 
Setting the DHW temperature
Observe the operating instructions for the heating control unit 
included in the scope of delivery. There you can read:
▶ How to set the operating mode and the heating curve for outdoor 
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▶ How to adjust the room temperature
▶ How to heat economically and save energy
DANGER: Danger of scalding!
▶ In normal operation, it is recommended to limit the DHW 
temperature to 122 °F (50 °C) to limit the risk of scalding.
▶ Only set temperatures up to 158 °F (70 °C) for thermal 
disinfection ( page 22).
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▶ Set the DHW temperature on the DHW thermostat  .
The set DHW temperature flashes on the display for 30 seconds.
Fig. 7  
If there is reason for concern for contamination from bacteria such as 
legionella, consider setting the DHW thermostat   to at least “e” 
(131 °F (55 °C)).
This setting ensures an economical and comfortable DHW 
generation. Consult your local water department or municipality for 
further information.
DHW thermostat Typical DHW temperatures
min approx. 59 °F (15 °C)
e approx. 131 °F (55 °C)
max approx. 158 °F (70 °C)
Table 4  
Always set the DHW temperature as low as possible. A lower setting 
on the thermostat means a higher rate of energy savings.
Furthermore, higher DHW temperatures result in increased limescale 
deposits and thereby may impair the function of the appliance (e.g. 
longer times for heating up or lower output).
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ECO button
Pressing and holding the ECO button until it lights up switches between Comfort 
mode and Economy mode.
•Comfort mode, ECO button is not lit (default setting)
In Comfort mode, the DHW tank has priority. The DHW tank is heated to the set 
temperature first. Then the appliance switches to central heating mode.
•Economy mode, ECO button lit
In Economy mode, the appliance alternates between central heating mode and 
DHW mode.
4.6 ZWB..-3A appliances (combi boilers): 
Setting the DHW temperature
▶ Set the DHW temperature on the DHW thermostat  .
The set DHW temperature flashes on the display for 30 seconds.
Fig. 8  
DHW thermostat Typical DHW temperatures
min approx. 104 °F (40 °C)
e approx. 122 °F (50 °C)
max approx. 140 °F (60 °C)
Table 5  
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ECO button
Pressing and holding the ECO button until it lights up switches between Comfort 
mode and Economy mode.
•Comfort mode (default setting)
The appliance is continually maintained at the set temperature. Consequently, 
DHW draws are immediate, however the appliance may run even if no DHW is 
being drawn.
•Economy mode, ECO button lights up
– DHW is only generated when DHW is drawn.
–On demand: Quickly open and close a DHW tap to signal the appliance to heat 
to the selected temperature. After a short wait DHW will be available.
4.7 Setting manual summer mode
In summer mode or warm weather shut down (WWSD), the heating zone pump and 
consequently central heating are switched off. DHW generation remains active 
following the DHW program.
▶ Make a note of the setting of the boiler high limit dial  .
The DHW on demand signal allows maximum gas and water savings.
NOTICE: Heating system at risk of freezing. In manual summer 
mode, only the appliance is protected from freezing.
▶ Observe frost protection measures where there is a risk of 
freezing ( page 20). 
						

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▶ Turn the boiler high limit dial   counterclockwise to  .
Fig. 9  
For further information, see the operating instructions for the heating control unit 
included in the scope of delivery.
4.8 Setting frost protection
Frost protection of the heating system:
▶ Leave the appliance switched ON; turn the boiler high limit dial   at least to 
position 1. 
Fig. 10  
For further information, see the operating instructions for the heating control unit 
included in the scope of delivery.
Alternatively if you prefer switching the appliance OFF:
▶ Ask a trained and certified heating contractor to mix anti-freeze (see installation 
instructions) into the heating water. All DHW pipes and DHW tank must be 
completely drained.
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