Control Unit; Requirements For The Control Unit; Control Unit Of Cfb 800/Cfb 900 Series (Accessories) - Bosch Uni Condens 8000 F Installation And Maintenance Instructions Manual

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Control unit

DANGER:
Danger to life and of system damage through faulty connections.
▶ Only carry out electrical work if you are properly qualified.
▶ Observe the local installation regulations.
▶ The system installer must issue a wiring diagram which records the
interfaces between heating output elements, burner, control unit
(CFB/CC) and additional safety equipment.
▶ Make sure that the electrical installations are suitable for wet areas.
DANGER:
Danger to life due to electric shock!
▶ Before opening the control unit or boiler, isolate the heating system
across all poles and secure against unintentional reconnection.
▶ Carefully route the cables/leads and capillary tubes.
▶ Ensure that the capillaries are never kinked.
▶ Create a permanent connection in accordance with the applicable
international installation standards and local regulations.
7.1

Requirements for the control unit

We recommend using a control unit from the CFB 800/CFB 900 or
CC 8000 series.
The purpose of optimum control unit settings is to achieve long burner
runtimes and avoid rapid temperature changes in the boiler. Gentle
temperature changes result in a longer service life of the heating system.
The control strategy of the control unit must therefore be prevented from
becoming ineffective, i.e. through the boiler temperature controller
switching the burner on and off.
Observe the following points when selecting the control unit.
• The control unit must ensure that the maximum internal boiler water
temperature and the high limit safety cut-out are at least 5 K apart.
• It must also be ensured that the control electronics rather than the
boiler temperature controller switch the burner on and off.
• The control unit must ensure that the burner is switched to low load
before a controlled shutdown. If this is not observed, the safety shut-
off valve (SAV) in the gas train may lock out.
• Select and adjust the control unit so as to allow a gentle start-up of
the boiler with a time delay when the system is cold. The heat energy
demand must only be switched on with time delay.
• After the burner demand, an automatic timer (for example) should
limit the burner to low load for a period of approx. 150 seconds. A
restricted heat demand will prevent uncontrolled starting and
stopping of the burner.
• It must be possible to show the number of burner starts at the control
unit used (or alternatively at the burner control unit).
• The maximum number of burner starts must be monitored. There
should be a maximum of 6 burner starts per hour (averaged over
burner runtime on one day). If the number of starts is higher, the user
should be notified. The system must be checked to find out whether
the number of burner starts can be reduced. The customer service of
the manufacturer can provide assistance with optimisation of the
system.
Uni Condens 8000 F – 6720867056 (2016/10)
▶ Maintain the minimum differential between the selected shutdown
temperature of the high limit safety cut-out, the temperature
controller, the maximum boiler temperature and the maximum
temperature demand ( CFB 800/CFB 900: tab. 12, page 27;
CC 8000: tab. 14, page 31).
The maximum boiler temperature can be selected in the user interface of
the control unit in the "Boiler parameters" menu, under the menu item
"Max. shutdown temperature".
▶ Select set temperatures for the heating circuits that are as low as
possible.
▶ Start heating circuits at 5 minute intervals (e.g. when starting up
in the mornings).
7.2 Control unit of CFB 800/CFB 900 series
(accessories)
The position of the terminal strip in control units of the CFB 800/CFB
900 series varies, depending on the control unit, but the labelling of the
terminal strips is identical. The terminal strip is easy to identify after the
control unit has been opened.
You can use the following control units with the boiler:
• CFB 840
• CFB 810
• CFB 810
• CFB 830
The control unit can be fitted either on top of the boiler or, with the
control unit holder (accessory), onto the boiler side.
When using the side-mounted control unit holder:
▶ Observe the attached installation instructions.
Control unit
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