Viessmann Vitocal 350-A Installation And Service Instructions Manual page 220

Connection and wiring diagrams
Safety chain, control circuit, main power...
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 ~CLOSED, external heat
source
G Heating circuit pump for heating
circuit without mixer A1
H Circulation pump for cylinder heat-
ing
220
(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 215
Z For continuation of control circuit,
see following illustration
aCH Control module, instantaneous
heating water heater (plug in cable
harness)