Viessmann VITOTRONIC 100 GC1B Installation And Service Instructions Manual page 69

Vitotronic 100, GC1B Installation and Service
Multi Boiler System – Connecting an External Control Unit
Legend
A Control unit
B Junction box
C Burner control unit
D Burner activation - base load
E Isolation valve open
F BMS - Burner modulation control
External Burner Start – Base Load
Contact at terminals "1" and "2" of plug aVD:
Contact closed:
The burner is started with base load.
An external modulation controller regulates the load-
dependent modulation.
The boiler water temperature is limited by the electronic
maximum temperature limiter, if that is set below that
of mechanical adjustable high limit R.
Contact open:
The burner is switched OFF.
Enable Boiler, Isolation Valve
Contact at terminals "2" and "3" of plug aVH:
Contact closed:
The isolation valve opens.
Contact open:
The isolation valve is closed after approx. 5 min.
The burner cannot be switched ON externally;
a minimum temperature will not be maintained.
Installation Sequence
(continued)
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