External "Mixing Valve Closed"/"Mixing Valve Open; External Changeover Of Multi Stage/Modulating Burners - Viessmann VITOTRONIC300 Installation And Service Instructions Manual

Installation Sequence

External "Mixing Valve Closed"/"Mixing Valve Open"

Connection at plug aVD.
Legend
A External "Mixing valve open" (floating contact)
B External "Mixing valve closed" (floating contact)
Codes
External "Mixing valve open"
This function is assigned to the heating circuits via
coding address "9A" in the "General" group.

External Changeover of Multi Stage/Modulating Burners

Connection via plug aVH.
Legend
A External changeover (floating contact)
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Vitotronic 300, GW2B Installation and Service
Note: 'Live' contacts lead to short circuits or phase failure.
The external connection must be floating.
External "Mixing valve closed"
This function is assigned to the heating circuits via
coding address "99" in the "General" group.
Note: 'Live' contacts lead to short circuits or phase
failure. The external connection must be floating.
Code
Set code "02:2" in group 2 "Boiler".
Contact open: modulating mode
Contact closed: two stage mode
Note: When scanning the burner version, the address
for modulation appears even after an external
changeover (no rewriting).