Hydraulic Connection; Control System; Dhw Heating - Bosch UT-L 1 Technical Manual

48 | System examples
Abbr. Meaning
RWT Condensing heat exchanger return
SH Motorised blending valve
SR Actuator, return temperature raising facility
Actuator, return temperature raising facility
SRWT
for condensing heat exchanger
THV Thermostatic valve
VK Boiler flow
VR Return distributor
VV Flow distributor
VWT Condensing heat exchanger flow
WH Low loss header (hydraulic balancing line)
Table 26 Summary of frequently used abbreviations
9.1.1

Hydraulic connection

Heating circuit pumps
Size pumps in central heating systems in accordance
with current technical rules.
Temperature sensor
A strategy flow temperature sensor (FVS) should be
positioned as close as possible to the boiler system. This
stipulation does not apply if hydraulic balancing has
been provided via a low loss header. Long distances
between the boiler system and the strategy flow
temperature sensor have a negative effect on the control
characteristics, especially in the case of boilers with
modulating burners.
Allow for the temperature sensors required for raising
the return temperature as immersion sensors.
Dirt traps
Deposits in the heating system can lead to local
overheating, noise and corrosion. Any resulting boiler
damage falls outside the warranty obligations.
To remove dirt and sludge, flush an existing heating
system thoroughly prior to installing and commissioning
a boiler. In addition, we recommend the installation of
dirt traps or a dirt separator.
Dirt traps retain contaminants and thereby prevent
faults in control devices, pipework and boilers. Fit these
near the lowest point of the heating system in an easily
accessible position. Clean the dirt traps every time the
heating system is serviced.
The function of a dirt trap can be fulfilled by
a hydraulic balancing line (low loss header)
( page 56).
9.1.2

Control system

The operating temperatures should be controlled with
the Bosch CFB control unit in weather-compensated
mode. It is also possible to control individual heating
circuits in room temperature-dependent mode (with a
room temperature sensor in a reference room). For this,
the actuators and heating circuit pumps are constantly
actuated by the CFB control unit. The number and
version of heating circuits that can be controlled depend
on the boiler control.
6 720 807 794 (2013/04)
The CFB control unit can also actuate the burners,
whether they are 2-stage or modulating pressure-jet
burners. Different types of burners can also be
combined in multi burner systems.
The electrical connection of 3-phase burners and 3-
phase pumps must be made on site. These are switched
by the CFB control unit (230 V).
For more detailed information, see the technical guides
to the control units.
9.1.3

DHW heating

If the DHW temperature is controlled with a CFB control
unit and it is designed accordingly, special functions are
possible, such as the actuation of a DHW circulation
pump or thermal disinfection to prevent the growth of
legionella.
For more detailed information on this
subject, see the technical guide "Sizing and
selecting DHW cylinders".
UNIMAT