Viessmann VITOCAL 151-A Installation And Service Instructions Manual page 124

Indoor unit maintenance
Overview of internal components
L
K
H
Fig. 74
Expansion vessel
A
Integrated buffer cylinder
B
Draining indoor unit on the secondary side
Danger
Heating water escaping uncontrolled may cause
scalding.
Allow the heating system to cool down before
draining.
Removing hydraulic components and EPP insulating parts
When replacing hydraulic components and EPP insu-
lating parts, first fold out or remove electrical compo-
nents if required: See chapter "Removing the program-
ming unit and electronics module".
Separate installation instructions are supplied with
some components.
124
M
A
B
C
D
E
F
G
Pressure sensor
C
D 4/3-way valve
High limit safety cut-out (STB), instantaneous
E
heating water heater
Flow sensor
F
Secondary pump
G
Instantaneous heating water heater
H
Safety valve
K
Flow temperature sensor
L
M Return temperature sensor
Set the 4/3-way valve in turn to
no longer comes out.
, and until water