Unimat Ut-L Boiler With Flue Gas Heat Exchanger Or Condensing Heat Exchanger: Return Temperature Raising - Bosch UT-L 1 Technical Manual

9.12 UNIMAT UT-L boiler with flue gas heat exchanger or condensing heat exchanger: return
temperature raising
Fig. 46 Installation of the heat exchanger in the UNIMAT UT-L boiler (list of abbreviations
The circuit diagram is only a schematic
illustration! Information regarding all
system examples  page 47 ff.
AREA OF APPLICATION
• UNIMAT UT-L boiler with flue gas heat exchanger or
condensing heat exchanger
• Oil/gas combi burners
Brief description of the system
• The operating conditions of the flue gas heat
exchanger are safeguarded with at low mains return
temperatures by a separate actuator in conjunction
with a return temperature control unit
Function description
In heating systems where the return temperature can be
very low, the additional SRWT return actuator is
required in the connection pipework of the ECO 7 heat
exchanger or the ECO 6 condensing heat exchange on
the water side. The return temperature control with 3-
step signal output monitors the minimum return
temperature, which depends on the type of flue gas heat
exchanger or on the fireplace. If the temperature falls
below the minimum return temperature of 60 °C, the
mixer closes. The cold return water cannot enter the
ECO 6 or ECO 7. If the temperature in this circuit rises
above 60 °C, the mixer enables the system return.
UNIMAT
RK VK
VWT
RWT
FR
Special design information
• If the SRWT actuator is installed between the boiler
and flue gas heat exchanger, an additional safety valve
and pressure gauge are required at the flue gas heat
exchanger.
• Control of the actuator SRWT should be arranged on
site or in conjunction with a control panel.
• Size the pump for the flue gas heat exchanger
according to its pressure loss and the pressure loss in
the circuit.
• Route away the condensate that occurs in the flue
system separately and neutralise it ( page 82 ff.).
• The flue gas heat exchanger pump is actuated in
parallel to the burner.
HK
THV
FV
PH
SH
SRWT
PWT
6 720 642 347-59.1il

page 47)
System examples | 65
VV
VR
6 720 807 794 (2013/04)