External Block Via Switching Contact; External "Mixer Closed"/"Mixer Open - Viessmann Vitotronic 300 Installation And Service Instructions Manual

Installation Sequence
External Blocking via Switching Contact
A Floating contact
B Plug aVD on control unit
A Floating contact
B Extension EA1

External "Mixer Closed"/"Mixer Open"

A External "Mixer open" (floating contact)
B External "Mixer closed" (floating contact)
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Vitotronic 300, GW5B Installation and Service
Connection options:
Plug aBÖ
Plug aVD
Extension EA1 (accessory)
Connection
Note: 'Live' contacts lead to short circuits or phase
failure. The external connection must be floating.
Closing this contact leads to a controlled burner shutdown.
Note: The heating system has no frost protection while it
is blocked. The boiler is not held at the lower boiler
water temperature.
Codes
Plug aVD
Set coding address "99" in
the "General" group.
Connection at plug aVD
Note: 'Live' contacts lead to short circuits or phase
failure. The external connection must be floating.
Codes
External "Mixer open"
This function is assigned
to the heating circuits via
coding address "9A" in the
"General" group.
Extension EA1
Set "5D", "5E" or "5F"
to 3 or 4 in the "General"
group.
External "Mixer closed"
This function is assigned
to the heating circuits via
coding address "99" in the
"General" group.