Viessmann VITOTRONIC 100 GC1B Installation And Service Instructions Manual page 67

Vitotronic 100, GC1B Installation and Service
Multi Boiler System – Connecting an External Control Unit
Legend
A Boiler enable (dry contact)
Legend
A Burner stage 1 "ON"
B Burner stage 2 "ON"
C Boiler enable
Motorized isolation valve "Open" or "Close"
Enable Boiler, Isolation Valve
Contact at terminals "2" and "3" of plug aVH:
Contact closed:
– Vitocrossal:
The isolation valve opens.
– Low temperature boiler:
Initially, the preheat function for lag boilers is activated.
After the preheat function has expired, the minimum
boiler water temperature will be maintained and the
burner stages can be controlled externally.
The isolation valve opens.
Contact open:
The isolation valve is closed after approx. 5 min.
Burner stages cannot be switched ON externally;
a minimum temperature will not be maintained.
Make connection at plug aVH.
Note: This contact must always be closed on the lead
boiler.
Closed Contact
Boiler enabled and
A
held at its minimum
temperature. The
isolation valve opens.
External Burner Start – Burner Stage 1
Contact at terminals "1" and "2" of plug aVD:
Contact closed:
Burner stage 1 is switched on.
Burner stage 2 is switched ON only for maintaining
the minimum temperature.
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:
Burner stage 1 is switched off.
External Burner Start – Burner Stage 1 and 2
Contact at terminals "2" and "3" of plug aVD:
Contact closed:
Both burner stages are switched ON.
The boiler water temperature is limited by the
electronic maximum temperature limiter, if it is set
below that of mechanical control thermostat "R".
Burner stage 2 is switched OFF 2 K sooner.
Contact open:
Burner stages 1 and 2 are switched OFF.
External Demand Via Switching Contacts
Connection at plug aVD/aVH of the control unit.
The set boiler water temperature is adjusted via code
"9b" in category 1 "General".
Two-Stage Burner
A, B and C are dry contacts of the higher control
unit.
Installation Sequence
(continued)
Open
The isolation valve is
closed after approx.
5 min. External burner
start not possible.
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