Functional Description - Viessmann VITODENS 222-F Service Instructions Manual

Outdoor Reset Programming Unit

Functional Description

32
Vitodens 222-F B2TB 19 and 35 Service
Heating mode
The control unit determines a set boiler water temperature
subject to outside temperature or room temperature (if a
room temperature-dependent remote control is connected)
and to the slope/ shift of the heating curve.
The determined set boiler water temperature is transferred
to the burner control unit. From the set and actual boiler
water temperatures, the burner control unit calculates the
modulation shift and regulates the burner accordingly.
The electronic temperature limiter inside the burner
control unit limits the boiler water temperature.
Heating the DHW primary tank from cold
The heating circuit pump is switched ON and the three-
way diverter valve will be changed over, if the DHW tank
temperature sensor captures a temperature lower than the
defaulted set temperature.
H The DHW tank primary pump is switched ON if the
boiler water temperature ≥ set DHW temperature.
H The burner is switched ON if the boiler water
temperature ≤ set DHW temperature, and the DHW
tank primary pump is switched ON when the required
boiler water temperature is reached.
The primary DHW tank is heated up to the set DHW
temperature. Heating stops when the set temperatures
have been reached at the DHW tank temperature sensor
and at the outlet temperature sensor.
After heating, the DHW tank primary pump and the three-
way diverter valve remain ON for a further 30 sec.
Boosting when DHW is drawn off
When DHW is drawn off, cold water enters at the bottom
of the primary DHW tank.
The heating circuit pump is switched ON and the three-
way diverter valve is changed over, if the DHW tank
temperature sensor recognizes a temperature lower than
the set temperature.
H The DHW tank primary pump is switched ON if the
boiler water temperature ≥ set DHW temperature.
H The burner is switched ON if the boiler water
temperature ≤ set DHW temperature, and the DHW
tank primary pump is switched ON when the required
boiler water temperature is reached.
The DHW is controlled to the specified temperature via
the DHW tank temperature sensor.
The primary DHW tank continues to be heated up after
the draw off process has terminated, until the set
DHW temperature has been reached at the DHW tank
temperature sensor.
The DHW tank primary pump and the three-way diverter
valve remain ON for a further 30 sec.
Boosting DHW heating
The booster heating function is activated if a switching
period is selected for the fourth time phase.
The set temperature value for the heating boost is
adjustable in coding address "58".