Blocking Boiler Externally/Adding To The Boiler Sequence - Viessmann VITOTRONIC 300 Installation And Service Instructions Manual

Installation, Vitotronic 300, GW5B

Blocking Boiler Externally/Adding to the Boiler Sequence

Legend
A Blocking boiler externally (floating contact)
B Start boiler externally as the last one in the boiler
sequence (floating contact)
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Vitotronic 300, GW5B & MW1B Installation and Service
Connection at plug aVD.
Note: 'Live' contacts lead to short circuits or phase
failure. The external connection must be floating.
Contact A:
H Contact closed:
The boiler is removed from the boiler sequence.
The butterfly valve or the 3- way mixing valve are
closed for constant return temperature control.
Shunt pump or boiler circuit pump are switched off.
The heat demand has to be met by the other boilers.
Note: If all boilers are blocked or there is no other boiler
available for duty, there will be no frost protection
for the heating system.
H Contact open:
The boiler is integrated into the current boiler sequence.
Contact B:
H Contact closed:
The heat demand of the heating system is met by the
other boilers. This boiler is started if the output of these
boilers is insufficient.
H Contact open:
The boiler is integrated into the current boiler sequence.