Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 227

Overview of the PCBs and connection options
Terminals Function
X3.12 External demand to the
X3.13 heat pump; mixer OPEN;
or to exter- operating status change-
nal exten- over
sion H1
X2.2 ON/OFF switch
X2.3
X3.16
X3.17
X3.17 Fuse F1 6.3 A (slow)
X3.18
Connection and wiring diagrams
Explanation
Zero volt contact required:
■ Closed: Demand
■ Open: No demand
■ Breaking capacity 230 V, 2 mA
Connect on site
At the programming unit
(cont.)
227