Viessmann VITOTRONIC 100 Installation And Service Instructions Manual page 49

System version 16
Possible applications
For heating circuits with temperature
differentials y 20 K.
The cascade and cylinder control
must be provided by a higher control
unit.
The Vitocrossal 300 (lead boiler) and
the next low temperature boiler
should be operated via a
weather−compensated control
system with modulating boiler water
temperature and load−dependent
sequential control
modulating burners are regulated.
(cont.)
two−stage or
Heating system designs
Vitocrossal 300 are equipped with
two return connectors. The heating
circuits with the higher return
temperature are connected to the
upper return connector and those
with lower return temperatures to
the lower return connector. Note:
connect at least 15% of the rated
output to the lower return connector.
The Therm−Control temperature
sensor of the low temperature boiler
regulates the boiler circuit pump.
The boiler circuit pump is switched
OFF when the Therm−Control
temperature defaulted by the boiler
coding card is not achieved.
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