Heating Circuit Control - Viessmann Vitotwin 300-W Installation And Service Instructions For Contractors

Function description
Cylinder temperature control
Auxiliary DHW heating function
When the auxiliary function for DHW
heating is active (code 1640), the DHW
cylinder is heated up at preset times
(codes 1641, 1642, 1644) to the set aux-
iliary function for DHW heating (code
1645) value. The set auxiliary function
for DHW heating value is maintained
over the set dwell time (code 1646). If the
auxiliary function for DHW heating circu-
lation pump is switched on (code 1647),
the circulation pump is switched on dur-
ing the auxiliary function for DHW heat-
ing. If DHW heating is switched off, the
auxiliary function for DHW heating starts
again as soon as DHW heating is turned
on again.
Frost protection
If the temperature in the DHW cylinder
falls to 5 °C, DHW is heated to 8 °C.

Heating circuit control

The set flow temperature of the heating
circuits is determined by the following
parameters:
■ Outside temperature
■ Set room temperature
Coding addresses that influence the heating circuit control
include:
830, 1130, 1430
158
(cont.)
Note
Whilst the auxiliary function for DHW
heating is active, there is a risk of scald-
ing in the vicinity of draw-off points.
■ Operating mode
■ Heating curve
The flow temperature of heating circuits
with mixers is controlled by gradually
opening and closing the mixer.
For a description, see codes overview.