Viessmann VITOTRONIC 100 GC1B Installation And Service Instructions Manual page 68

Installation Sequence
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 Burner Modulation up
G Burner Modulation down
Enable Boiler, Isolation Valve
Contact at terminals "2" and "3" of plug aVH:
Contact closed:
Initially, the preheat function for lag boilers is activated.
After the preheat function has expired, the minimum
boiler water temperature is maintained and the burner
is controlled by the on-site modulation controller.
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.
Vitocrossal With Modulating Burner
(on-site modulation controller)
Burner Connection:
Connect plug fA of Vitotronic 100 to the burner.
Plug lÖ of the Vitotronic 100 remains unallocated.
Via external demand aVH, the on-site modulation
controller starts the burner with base load.
68
Vitotronic 100, GC1B Installation and Service
Refer to the burner Installation Instructions.
Low Temperature Boiler With Modulating Burner (on-site
modulation controller)
Burner Connection:
Connect plug fA of Vitotronic 100 to the burner.
Plug lÖ from the Vitotronic 100 via modulation
controller (on site) to plug lÖ on the burner.
Via external demand aVD, the on-site modulation
controller starts the burner with base load.
External Burner Start – Base Load
Contact at terminals "1" and "2" of plug aVD:
Contact closed:
The burner is started with base load.
To maintain the minimum temperature, the burner
is switched to full load via the Vitotronic 100.
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.
(continued)