Heating Mode; Heating The Dhw Loading Cylinder From Cold; Reheating When Dhw Is Drawn Off; Boosting Dhw Heating - Viessmann Vitodens 222-F Installation And Service Instructions For Contractors

Weather-compensated control unit

Heating mode

The control unit determines a set boiler water tempera-
ture subject to outside temperature or room tempera-
ture (if a room temperature-dependent remote control
is connected) and to the slope
curve.
The determined set boiler water temperature is trans-
ferred to the burner control unit. From the set and
actual boiler water temperatures, the burner control
unit calculates the modulation level and regulates the
burner accordingly.

Heating the DHW loading cylinder from cold

The heating circuit pump is switched ON and the 3-
way diverter valve will be changed over, if the cylinder
temperature sensor captures a temperature lower than
the defaulted set value.
■ The cylinder loading pump is switched ON if the
boiler water temperature
■ The burner is switched ON if the boiler water temper-
ature set cylinder temperature, and the cylinder
≤
loading pump is switched ON when the required
boiler water temperature is reached.

Reheating when DHW is drawn off

When DHW is drawn off, cold water enters the lower
section of the loading cylinder.
The heating circuit pump is switched ON and the 3-
way diverter valve is changed over, if the cylinder tem-
perature sensor captures a temperature lower than the
defaulted set value.
The cylinder loading pump is switched ON if the
■
boiler water temperature
■ The burner is switched ON if the boiler water temper-
ature set cylinder temperature, and the cylinder
≤
loading pump is switched ON when the required
boiler water temperature is reached.

Boosting DHW heating

This function is activated by specifying a second set
DHW temperature via coding address 58 in group
"DHW" and activating the fourth DHW phase for DHW
heating.
(cont.)
level of the heating
/
set cylinder temperature.
≥
set cylinder temperature.
≥
The electronic temperature limiter inside the burner
control unit limits the boiler water temperature.
The loading cylinder is heated up to the set cylinder
temperature. Heating stops when the specified temper-
ature has been reached at the cylinder temperature
sensor.
After loading has stopped, the cylinder loading pump
and the 3-way diverter valve remain on for a further
30 s.
DHW is regulated to the set temperature via the outlet
temperature sensor.
After the draw off process has ended the loading cylin-
der continues to be heated up, until the set DHW tem-
perature has been reached at the cylinder temperature
sensor.
The cylinder loading pump and the 3-way diverter
valve remain ON for a further 30 s.
Heating is boosted during the periods selected in this
time phase.
Function description
121