Viessmann VITOTRONIC 100 Installation And Service Instructions Manual page 78

Installation
External hook−up in multi−boiler systems without LON
143
A Vitotronic 100
B Burner control
78
146 Zero volt contacts of the higher control unit
with modulation controller:
Enable boiler, open or close the butterfly
valve
Burner stage 1 (base load) ON
Modulation controller:
Reduce burner output
Increase burner output
(cont.)