Viessmann Vitodens 333 Service Instructions Manual page 91

Constant temperature control unit
Heating the DHW storage cylinder from cold
The heating circuit pump is switched
ON and the three-way diverter valve
will be changed over, if the cylinder
primary temperature sensor captures
a temperature lower than the set tem-
perature.
At a boiler water temperature ≥ set
&
DHW temperature, the cylinder pri-
mary pump will be switched ON.
At a boiler water temperature ≤ set
&
DHW temperature, the burner will
be switched ON and, after the
required boiler water temperature
has been reached, the cylinder pri-
mary pump will be switched ON.
Reheating when DHW is drawn off
When DHW is drawn off, cold water
enters at the bottom of the cylinder.
The heating circulation pump is
switched ON and the three-way diver-
ter valve is changed over, if the cylin-
der primary temperature sensor
captures a temperature lower than the
set temperature.
At a boiler water temperature ≥ set
&
DHW temperature, the cylinder pri-
mary pump will be switched ON.
At a boiler water temperature ≤ set
&
DHW temperature, the burner will
be switched ON and, after the
required boiler water temperature
has been reached, the cylinder pri-
mary pump will be switched ON.
Function description
(cont.)
The cylinder is then heated up to the
set DHW temperature. Heating stops
when the set temperature has been
reached at the cylinder primary tem-
perature sensor and at the outlet tem-
perature sensor.
After heating, the cylinder primary
pump and the three-way diverter
valve remain ON for a further 30 s.
The DHW is regulated to the set tem-
perature via the cylinder primary tem-
perature sensor.
The cylinder continues to be heated
up after the draw-off process has
ended, until the set DHW temperature
has been reached at the cylinder pri-
mary temperature sensor.
The cylinder primary pump and the
three-way diverter valve remain ON
for a further 30 s.
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