Viessmann VITODENS 333-F WS3A Service Instructions Manual page 94

Function description
Weather-compensated control unit
To 74 °C by the control thermostat
inside the burner control unit.
To 82 °C by the electronic tempera-
ture limiter inside the burner control
unit.
To 100 °C by the temperature limiter
in the safety chain (interlocks the
burner control unit).
Heating the DHW primary cylinder from cold
The heating circuit pump is switched
ON and the three-way diverter valve
will be activated, if the cylinder tem-
perature sensor recognises a tem-
perature lower than the set
temperature.
The DHW primary pump is switched
on if the boiler water temperature
set DHW temperature.
The burner is switched on if the boil-
er water temperature
temperature, and the DHW primary
pump is switched on when the
required boiler water temperature is
reached.
Boosting when DHW is drawn off
When DHW is drawn off, cold water
enters at the bottom of the cylinder.
The heating circuit pump is switched
ON and the three-way diverter valve
is activated, if the cylinder tempera-
ture sensor recognises a temperature
lower than the set temperature.
94
(cont.)
The cylinder is then heated up to the
set DHW temperature. Heating stops
when the set temperature has been
reached at the cylinder temperature
sensor and at the outlet temperature
sensor.
After heating, the cylinder primary
pump and the three-way diverter
valve remain ON for a further 30 s.
set DHW
The DHW primary pump is switched
on if the boiler water temperature
set DHW temperature.
The burner is switched on if the boil-
er water temperature
temperature, and the DHW primary
pump is switched on when the
required boiler water temperature is
reached.
The DHW is controlled to the specified
temperature via the cylinder tempera-
ture sensor.
set DHW