Weather-Compensated Control Unit - Viessmann Vitodens 333 Service Instructions Manual

Function description

Weather-compensated control unit

Heating mode
The control unit determines a set boi-
ler water temperature subject to out-
side temperature or room temperature
(if a room temperature-dependent
remote control is connected) and the
slope/level of the heating curve. The
determined set boiler water tempera-
ture is then transferred to the burner
control unit. From the set and actual
boiler water temperatures, the burner
control unit calculates the modulation
level and controls the burner accord-
ingly. The burner control unit limits the
boiler water temperature: through the
control thermostat to 74 °C and
through the electronic temperature
limiter to 82 °C. The thermocouple in
the safety chain locks out the burner
control unit at a boiler water tempera-
ture of 100 °C.
Heating the DHW loading 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.
Then,
at a boiler water temperature ≥ than
&
the set DHW temperature, the DHW
loading pump is switched ON.
at a boiler water temperature ≤ than
&
the DHW set temperature, the bur-
ner is switched ON and, after the
required boiler water temperature
has been reached, the DHW loading
pump is switched ON.
96
The cylinder is then loaded up to the
set DHW temperature. Heating stops
when the set temperature has been
reached at the cylinder temperature
sensor and at the loading temperature
sensor. After loading, the DHW load-
ing pump and the three-way diverter
valve remain ON for a further 30 s.
Reheating 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.
Then,
at a boiler water temperature ≥ than
&
the set DHW temperature, the DHW
loading pump is switched ON.
at a boiler water temperature ≤ than
&
the DHW set temperature, the bur-
ner is switched ON and, after the
required boiler water temperature
has been reached, the DHW loading
pump is switched ON.
The DHW is regulated to the set tem-
perature via the loading temperature
sensor. The cylinder continues to be
heated up after the draw off process
has ceased, until the set DHW tem-
perature has been reached at the
cylinder temperature sensor. The
DHW loading pump and the three-way
diverter valve remain ON for a further
30 s.