Viessmann Vitotronic 100 GC1 Installation And Service Instructions Manual page 20

Heating system designs
System version 5
(cont.)
Possible applications
Vitocrossal 300 is operated via a
Viessmann boiler control unit with
outdoor reset function, modulating
boiler water temperature, and
load-dependent sequential
control – two-stage or modulating
burners are controlled.
Vitocrossal 300 is equipped with two
return connections. The heating circuits
with the higher return temperature are
connected to the upper return
connection, and those with lower
return temperatures to the lower return
plug. Please note: Connect at least
15% of the rated output to the lower
return connection.
Due to the LON-BUS communication
between controls, a boiler supply
temperature is automatically set.
This temperature is based on the
highest required mixing valve circuit
temperature plus adjustable differential.
IMPORTANT
The connection diagram is only a
recommendation and needs to be
verified for completeness and
functionality at the installation site.
Single-phase and three-phase pumps
must be connected with field supplied
motor contactors and/or motor
starters.
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