System examples | 61
6 720 807 794 (2013/04)UNIMAT
9.8 2-boiler system with two UNIMAT UT-L boilers: boiler circuit control unit with hydraulic
separation
Fig. 42 System example for a 2-boiler system with boiler circuit control unit and hydraulic separation (list of
abbreviations
page 47)
AREA OF APPLICATION
•UNIMATUT-L boiler
• boiler circuit control unit
– Maintaining the operating conditions
– Enabling of burner stages
• Hydraulic separation
Brief description of the system
• Minimum return temperature controlled via a
separate actuator in the boiler circuit and a boiler
circuit pump
• Either serial or parallel operating mode
• 2-stage or modulating burner mode
• Boiler sequence can be reversed
• Hydraulic shut-off of the lag boiler with time delay
• Automatic or weather-compensated load limitation
• Control of heating circuit using CFB control unit or on-
site control unit
Function description
The 3-way valve is actuated to control the return
temperature. The return temperature sensor measures
the boiler return temperature. If this falls below the set
value, the flow rate to the return is constantly restricted
by actuating the 3-way valve. If the return temperature
rises above the set value, the 3-way valve is reopened
and the flow rate to the heating circuit increases. Any
boilers not in operation are hydraulically shut off.
Special design information
• Allow for a low loss header.
• The boiler circuit pump run-on time after burner
shutdown should be five minutes for the lag boiler,
and 30-60 minutes for the lead boiler.
• We recommend distributing the total rated output
between the boilers so each has 50 % (maximum 60/
40 %).
• This scheme can also be used if a third boiler is
connected.
VK
RK
VK
RK
FZ
FK
FVS
FK
FZ
6 720 803 977-22.1itl
HK
PK
SH
PH
FV
THV
VV
VR
WH
PK
SR
SR
039 BFC019 BFC
+ CMC 930
The circuit diagram is only a schematic
illustration! Information regarding all
system examples page 47 ff.
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