Viessmann Vitodens 333-F Service Instructions Manual page 101

Constant temperature control unit
Heating the DHW primary cylinder from cold
The heating circuit pump is switched
ON and the three-way diverter valve
will be changed over, if the cylinder
temperature sensor captures a tem-
perature lower than the defaulted set
temperature.
& The cylinder primary pump is
switched ON if the boiler water tem-
perature ≥ set DHW temperature.
& The burner is switched ON if the
boiler water temperature ≤ set DHW
temperature, and the cylinder pri-
mary pump is switched ON when
the required boiler water tempera-
ture is reached.
Boosting when DHW is drawn off
When DHW is drawn off, cold water
enters at the bottom of the primary
cylinder.
The heating circuit pump is switched
ON and the three-way diverter valve
is changed over, if the cylinder tem-
perature sensor recognises a tem-
perature lower than the set
temperature.
& The cylinder primary pump is
switched ON if the boiler water tem-
perature ≥ set DHW temperature.
& The burner is switched ON if the
boiler water temperature ≤ set DHW
temperature, and the cylinder pri-
mary pump is switched ON when
the required boiler water tempera-
ture is reached.
Function description
(cont.)
The primary cylinder is heated up to
the set DHW temperature. Heating
stops when the set temperatures have
been reached at the cylinder tempera-
ture sensor and at the outlet tempera-
ture sensor.
After heating, the cylinder primary
pump and the three-way diverter
valve remain ON for a further 30 s.
The DHW is controlled to the specified
temperature via the cylinder tempera-
ture sensor.
The primary cylinder continues to be
heated up after the draw off process
has terminated, until the set DHW
temperature has been reached at the
cylinder temperature sensor.
The cylinder primary pump and the
three-way diverter valve remain ON
for a further 30 s.
101