Viessmann VITOCAL 300-A Installation And Service Instructions Manual page 181

Safety chain, control circuit, main power circuit
A
Switched phase
B
External heat source control
(zero volt)
C
Instantaneous heating water
heater control (accessory) stage
2
D
N/A
E Mixer |OPEN, external heat
source
F Mixer ~CLOSE, external heat
source
G
Heating circuit pump for heating
circuit without mixer A1
H
Circulation pump for cylinder
heating
Connection and wiring diagrams
(cont.)
I
DHW circulation pump ("Wtimer
DHW Circ.")
J
Central fault message (zero volt)
K
Compressor control
L
Instantaneous heating water
heater control (accessory) stage
1
X
For safety chain connection, see
page 176
Z
For continuation of control cir-
cuit, see following illustration
aCH Control module, instantaneous
heating water heater (plug in
cable harness)
181