Viessmann Vitodens 222-F B2TA Installation And Service Instructions Manual page 151

Weather-compensated control unit
Reheating when DHW is drawn off
When DHW is drawn off, cold water
enters at the bottom of the primary
store.
The heating circuit pump is switched ON
and the 3-way diverter valve is changed
over, if the cylinder temperature sensor
recognises a temperature lower than the
set value.
■ The cylinder primary pump is switched
ON if the boiler water temperature ≥
set DHW temperature.
■ The burner is switched ON if the boiler
water temperature ≤ set DHW temper-
ature, and the cylinder primary 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 activat-
ing the fourth DHW phase for DHW heat-
ing.
Function description
(cont.)
DHW is regulated to the set temperature
via the outlet temperature sensor.
The primary store continues to be heated
up after the draw off process has termi-
nated, until the set DHW temperature
has been reached at the cylinder tem-
perature sensor.
The cylinder primary 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.
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