139
Heating mode
The Vitotronic control unit determines a set flow tem-
perature depending on the outside temperature or
room temperature (if a room temperature-dependent
remote control is connected) and the slope/level of the
heating curve.
The process control unit determines a heat demand
from the set flow temperature in the Vitotronic control
unit, the actual flow temperature and the flow rate. The
system keeps this heat demand at a constant average
over time.
This heat demand determines both the actual set flow
temperature and the operating mode within mixed
mode:
■
If more heat is required than is currently being sup-
plied, the system switches firstly into mixed mode
and then, if necessary, into condensing mode.
■
If the supplied heat is sufficient, the system remains
in or reverts to sorption mode.
■
If more heat than required is supplied, the appliance
switches off.
If the heat demand is so high that a sorption cycle
can be completed, the appliance switches on.
DHW heating
Irrespective of the selected operating mode, the set
flow temperature is increased automatically to 80 °C
when there is a heat demand for DHW heating.
If the set flow temperature cannot be achieved with a
sorption cycle, reheating takes place in condensing
mode.
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.
Heating is boosted during the periods selected in this
time phase.
Cooling the process circuit
If the temperature distribution in the appliance is in an
undefined state, the process circuit is cooled down
automatically to achieve a temperature level that is
balanced and as low as possible.
The secondary pump starts so that heat can be trans-
ferred to the secondary circuit. The low temperature
process pump starts and the control valve regulates to
a set flow temperature 5 K higher than the actual
return temperature.
If the evaporator temperature is higher than 3 °C, both
the primary pump and the evaporator pump start. This
balances out the temperatures in the sorption module.
After approx. 10 min, the temperatures in the process
flow, process return and sorber outlet will have con-
verged to within approx. 3 K.
This procedure starts in the following cases:
■
After running the commissioning assistant
■
When the appliance is switched on
■
At the start of the emissions test mode
■
On calling up the
"System functions"
(actuator test,
filling, venting, etc.)
■
On activation of the combustion controller parame-
ters (changing of code "11" in the
"General"
group)
■
When the burner control unit is reset
■
On acknowledgement of fault messages from the
process control unit or burner control unit
■
On ending service mode
■
Before and after sensor calibration
Function description
Control unit
(cont.)
5678 044 GB
Functions
Summary of Contents for D2RA
Page 113: ...113 Maintenance Checking the Vitotronic 200 H accessories cont 5678 044 GB Maintenance ...
Page 133: ...133 Parts lists Sorption module hydraulics cont 5678 044 GB Components ...
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