Viessmann VITOLADENS333-F Service Instructions Manual page 83

Control unit
(cont.)
Heating mode
The control unit calculates a set boiler
water temperature depending on the
outside temperature and/or the room
temperature (if a room temperature-
controlled remote control facility is
connected) and the slope/level of the
heating curve. The determined set
boiler water temperature is then trans-
ferred to the burner control unit.
DHW heating
The burner, the circulation pump and
the three-way valve are started or
changed over, if the cylinder tempera-
ture lies 2.5 K below the set cylinder
temperature.
Boosting DHW heating
The booster heating function is acti-
vated if a switching period is selected
for the fourth time phase.
Function description
The burner control unit calculates the
heat demand and controls the two-
stage burner accordingly. The burner
control unit limits the boiler water tem-
perature: to 74 °C by the temperature
controller, and to 82 °C by the electro-
nic temperature limiter. The tempera-
ture limiter of the safety chain locks
out the burner control unit at a boiler
water temperature of 100 °C.
The set boiler water temperature is
adjusted 20 K higher than the set
DHW temperature (adjustable via
coding address "60"). The burner will
be switched OFF and the circulation
pump run-on time will begin, if the
actual cylinder temperature exceeds
the set cylinder temperature by 2.5 K.
The set temperature value for the
heating boost is adjustable in coding
address "58".
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